Elementary Earth and Space Science Methods

Ted Neal

Elementary Earth and Space Science Methods by Ted Neal is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

1

Introduction

Introduction

Dear Future Science Teachers,

We created this book to help you as both a college student and a future teacher. Dr. Ted Neal asked us to help him create this resource from the perspective of students who have taken Science Methods II–what would we want in a textbook for this course? With this in mind, we have gathered and created resources to help you better understand science and feel confident in your abilities as a future teacher.

This book is divided into four parts which align with the Science Methods II course: Space Science, Earth Science, Climate Change, and Pedagogy. Within each part, the material is broken down into smaller chapters. Here you will find written explanations, video links, glossary terms, key takeaways, and practice quizzes to help you understand the material. This book is designed to be a flexible resource; use it as much or as little as you need throughout the course.

As Ted likes to say, science is everywhere and it is everything. We hope this book can help you on your journey as a learner and teacher of science.

Cheers,

Rachel Dunn, Jenny Haley, Ella McDonald, Ben Smith

Welcome to Space Science. This part is divided into four chapters:

1. Earth

2. The Moon

3. Our Solar System

4. Origins and the Universe

Additionally, there is a practice quiz at the end that covers the entire unit.

1

Earth

Heliocentrism vs Geocentrism

In early times, humans believed in geocentrism–the theory that Earth is at the center of the solar system, and the Sun and other planets revolve around it. During the Renaissance in the 1500s, Copernicus popularized the concept of heliocentrism–the theory that the Sun is at the center of the universe and Earth orbits the Sun.

Throughout Copernicus’ lifetime, the scientific community widely denied the theory of heliocentrism. A generation later, the Sun-centered theory became more commonly accepted when Galileo invented the telescope in 1609, making it easier to observe space. Additionally, Galileo made a variety of discoveries about our solar system that disproved the geocentric model of the universe. Despite these new discoveries, however, there was still significant pushback against heliocentrism, particularly from the Catholic Church.

At the time, the Church defended its stance on geocentrism because it believed Galileo’s discoveries left too many questions unanswered and did not explicitly prove heliocentrism. During this period, a case could still technically be made for geocentrism until technology advanced enough for scientists to discover more evidence supporting heliocentrism.

Additionally, the Church had certain clergy who interpreted parts of the Bible very literally, as if it were a science textbook rather than a theological work. Galileo’s claims were scandalous in their eyes because heliocentrism directly conflicted with certain biblical passages. For these reasons, the Church put Galileo on trial, convicted him of heresy, and sentenced him to house arrest for the remainder of his life. In 1822, the Church eventually accepted the theory of heliocentrism once there was enough scientific evidence to claim it as truth.

Key Takeaway

To remember the theories of heliocentrism and geocentrism, break down the names and look at the etymology.

- The root geo– means “earth”, and centr– means “center”. So, geocentrism is the theory in which Earth is at the center of the solar system.

- The root helio– means “sun”, and centr– means “center”. So, heliocentrism is the theory in which the Sun is at the center of the solar system.

Equinox & Solstice

There are 2 equinoxes and 2 solstices per year – Spring Equinox, Autumn Equinox, Winter Solstice, and Summer Solstice. Equinoxes (which sounds like the word equal) mark the day in which all of Earth receives an equal amount of sunlight–12 hours. This equal amount of sunlight occurs when the Equator is directly in line with the Sun. The Spring Equinox happens around March 20th and the Autumn Equinox happens around September 23rd each year.

Equinox
“Illumination of Earth by Sun on the day of equinox” by Przemyslaw “Blueshade” Idzkiewicz is licensed under CC BY SA-2.0

Solstices mark the days of the year in which a hemisphere receives the least amount of sunlight (aka the shortest day of the year) and the most amount of sunlight (aka the longest day of the year). These days occur when one of the tropic lines are directly in line with the Sun. In the Northern Hemisphere, the Winter Solstice (the day with the least sunlight, usually around December 21) occurs when the Tropic of Capricorn (the southern tropic line) is in line with the Sun. The Summer Solstice (the day with the most sunlight, usually around June 21) occurs when the Tropic of Cancer (the northern tropic line) is in line with the Sun.

Winter Solstice
“Illumination of Earth by Sun on the day of summer solstice in the northern hemisphere” by Przemyslaw “Blueshade” Idzkiewicz is licensed under CC BY SA-2.0

Summer Solstice
“Illumination of Earth by Sun on the day of summer solstice in the northern hemisphere” by Przemyslaw “Blueshade” Idzkiewicz is licensed under CC BY SA-2.0

Eclipses

Eclipses happen when light is blocked. There are two types of eclipse that we can see on Earth: solar eclipses and lunar eclipses.

To understand each type of eclipse, you must determine whether the Sun or Moon is being blocked.

- In a solar eclipse the Sun is being blocked–this happens when the Moon perfectly crosses between Earth and the Sun. A solar eclipse always occurs during a new moon.

Solar Eclipse
Image credit: “Total Solar Eclipse” by NASA

- In a lunar eclipse, the Moon is blocked when it passes through Earth’s shadow. When the Moon is in this position, the Sun’s light cannot reach it. A lunar eclipse always occurs during a full moon.

Lunar Eclipse
“Lunar Eclipse” by NASA’s Marshall Space Flight Center is licensed under CC BY-NC 2.0

For more explanation of lunar eclipses, watch the video below.

A YouTube element has been excluded from this version of the text. You can view it online here: https://pressbooks.uiowa.edu/methodsii/?p=36

Video credit: “Lunar Eclipse Essentials” by NASA is public domain

Seasons

Earth orbits in the same plane as the other planets in our solar system: the Plane of the Ecliptic. However, Earth’s is also tilted on it axis. This tilt never changes in relation to space, so different areas of Earth are tilted toward the Sun at different times of year. This is why we have seasons.

- If a hemisphere is tilted towards the Sun it gets more sunlight and it warms up–aka summer.

- If a hemisphere is tilted away from the Sun it gets less sunlight and it cools down–aka winter.

Additionally, the Northern and Southern Hemispheres have opposite seasons due to the tilt of Earth’s axis. When the Northern Hemisphere is tilted towards the Sun it is summer (this is winter in the Southern Hemisphere). When the Southern Hemisphere is tilted towards the Sun it is summer (this is winter in the Northern Hemisphere).

Earth’s seasons are explained in the image below.

Image credit: Seasons by NASA Space Place is public domain

Key Takeaways

- As Earth orbits around the Sun, different areas receive direct or indirect sunlight due to the tilt of Earth on its axis. This is what causes seasons.

- Earth’s distance away from the Sun does not cause the seasons.

2

The Moon

Phases of the Moon

The Moon orbits around Earth once every 28 days, or about once a month. Depending on where the Moon is in its orbit, it appears different from Earth. However, everyone on Earth sees the same phase of the Moon on the same day.

The phases of the moon are:

- New: The Moon’s face is not visible from Earth

- Crescent: Between a new moon and a quarter moon

- Quarter: From Earth, we can see half of the moon’s face which is a quarter of the entire moon

- Gibbous: Between a quarter moon and a full moon

- Full: All of the Moon’s face is visible from Earth

For the first half of this cycle, the visible part of the Moon waxes or grows larger. After reaching a full moon, the Moon wanes or grows smaller for the second of the cycle.

The image, below, shows the Moon’s phases.

“Moon Phases from Earth” by pmonaghan is licensed under CC-By-NC-ND 2.0

For further explanation of the Moon’s phases, watch the following video.

A YouTube element has been excluded from this version of the text. You can view it online here: https://pressbooks.uiowa.edu/methodsii/?p=38

Video credit: “The Moon” by Khan Academy is licensed under CC BY-NC-SA 3.0. Note: All Khan Academy content is available for free at khanacademy.org.

Characteristics of the Moon

- Distance from Earth: 239,000 miles

- Size: As seen in the image, below, the Moon is about 1/4 the size of Earth.

“The Earth and the moon with their size at the exact same scale” by Lsmpascal–
Own work is licensed under CC BY-SA 3.0.

- Composition:

- Very similar to Earth

- Has an iron core, mantle, and crust

- Surface: The Moon’s rocky surface is covered in dormant volcanoes and craters which are the results of impacts from meteorites and asteroids over billions of years. The Moon is covered with craters for two reasons:

1. It does not have an atmosphere to protect it from the impact of objects such as asteroids in space.

2. There is no wind on the Moon to erode existing craters.

- Climate: The Moon has no atmosphere, wind, or weather. Thus, the temperature can range from extremely hot to extremely cold since there is no atmosphere to protect it from the Sun’s heat or insulate the surface.

- Gravity: Remember, more mass=more gravity and less mass=less gravity. As such, the Moon has 1/6 of the gravity of Earth. This means if you weigh 60 lbs on Earth, you would weigh 10 lbs on the Moon.

- The Moon’s gravity, although weaker than Earth’s gravity, has enough pull to move water. This is what causes tides on Earth. As Earth rotates on its axis, the area on the near side of the Moon feels its gravity. As seen in the image below, this causes the water on that side–as well as the opposite side of Earth–to bulge out and create a high tide. As Earth continues to rotate, the gravitational pull weakens and the water recedes, creating a low tide. Since Earth completes one full rotation on its axis each day, most areas have two high tides and two low tides per day.

“Tidal Force” by NOAA SciJinks is public domain

Sides of the Moon

There are two sides of the moon: the near side (the side we can see from Earth) and the far side (also known as the dark side). The Moon does not create its own light; it gets light from the Sun. As such, the dark side is not actually dark–it is just called the dark side because we cannot see it from Earth.

The near side of the Moon (left) vs. the far side of the Moon (right). Image credit: Near and far side of the moon by NASA

Since Earth has a larger mass, it exerts a stronger gravitational pull on the Moon. Earth’s pull controls the Moon’s orbit so that the Moon rotates once on its axis in the same amount of time it takes to orbit Earth. Therefore, the same side of the Moon is always facing Earth and we have a near side and a dark side. This effect is called tidal locking.

Click this link to see animation of how tidal locking works as the Moon orbits Earth.

Near side of the Moon

Far side of the Moon

- The side we can see from Earth

- Not visible from Earth

- Thinner crust: The Moon was in a molten state when it was first created. This side of the Moon is closer to Earth, so it received more heat and cooled off more slowly.

- Thicker crust: This side of the Moon is farther from Earth, so it received less heat and cooled more quickly.

- Large dark spots called maria (singular is “mare”) were formed from ancient volcanic eruptions. The leftover basalt rock spread out and cooled forming the maria. Early astronomers thought these dark spots were actual seas and thus used the word mare which is Latin for sea.

- Rugged and marked with many small craters as a result of impacts from space debris.

Sputnik and the Space Race

On October 4th, 1957 the Soviet Union successfully launched Sputnik, the world’s first artificial satellite, into Earth’s orbit.  This successful launch of Sputnik sparked the Space Race between the Soviet Union and the United States. These two countries competed to get the first human to land on the Moon.

On January 31, 1958, the United States launched Explorer 1, a satellite that discovered the magnetic radiation belts around Earth. That same year, the United States created the National Aeronautics and Space Administration (NASA). In 1959, the Soviet Union launched Luna 2, the first spacecraft to land on the Moon. In April 1961, the Soviet astronaut Yuri Gagarin became the first person in space when he orbited Earth. Shortly after, astronaut Alan Shepard became the first American in space in May 1961.

The Space Race heated up and President John F. Kennedy claimed that the United States would put a man on the Moon before the end of the decade. In 1962, American astronaut John Glenn successfully orbited the Earth. In 1968, American mission Apollo 8 orbited the Moon. Finally, in 1969, the American mission Apollo 11 successfully landed the first two people on the Moon: astronauts Neil Armstrong and Buzz Aldrin.

Interesting Fact

Dr. James Van Allen from the University of Iowa created the radiation detector that launched on the Explorer 1 satellite. This led to the discovery of magnetic radiation belts around Earth which are known as Van Allen radiation belts in his honor. Van Allen Hall on Iowa’s campus is also named after him.

Women and Space

Traditionally, the story of the Space Race features male scientists and astronauts. However, women have played a key role in the history of American space exploration. NASA mathematicians Katherine Johnson and Dorothy Vaughan along with engineer Mary Jackson were key members of the team that launched John Glenn into space in 1962. In addition to this mission, these women had long careers at NASA. Their stories have recently been popularized in the movie Hidden Figures.

Katherine Johnson by NASA

Mary Jackson by NASA

Dorothy Vaughan by NASA

Initially, women were seen to have a physical advantage as astronauts; they tend to be lighter, shorter, and consumer less food. In 1960, astronaut Jerrie Cobb had logged twice as many flying hours as John Glenn. But NASA made a requirement that astronauts had to be military pilots, a job only men could have. A group of 13 female astronauts, including Cobb, was gathered and subjected to the same tests as the male astronauts. The women passed all of the tests, and in many cases, performed better than the men. Still, NASA refused to support the female astronauts. In 1983, Sally Ride became the first female astronaut in space.

Sally Ride by NASA

Jerrie Cobb by SDASM Archives

3

Our Solar System

The Milky Way

A galaxy is a collection of billions of stars, gas, and dust held together by gravity in space. Our solar system is located in the Milky Way Galaxy. The Milky Way is a large spiral galaxy; it got its name because it appears as a milky band of light in the sky. There are hundreds of billions of stars in our galaxy. Our Sun, Earth, and all the planets are located halfway between the center and the outer edge on a small partial arm called the Orion Spur. At the center of the Milky Way is a supermassive black hole named Sagittarius A which has a mass of 4 million suns.

Image of the Milky Way Galaxy taken in Chile
“La Silla Dawn Kisses the Milky Way” by ESO/B. Tafreshi is licensed under CC BY 4.0

Spiral shape of the Milky Way Galaxy. Our solar system is located on the Orion Spur. “The Milky Way Galaxy” by NASA/JPL-Caltech/R. Hurt

Planets

Planets in the Solar System “A representative image of the solar system with sizes, but not distances, to scale” by WP is licensed under CC BY-SA 3.0

There are 8 planets in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. To remember the order of the planets (closest to farthest from the sun), use the acronym “My Very Educated Mother Just Served Us Nutella.”

The four inner planets–Mercury, Venus, Earth, and Mars–are rocky planets because they have a solid surface. The four outer planets–Jupiter, Saturn, Uranus, and Neptune–are gaseous planets because they are composed of gases, mainly hydrogen and helium. Notice that the rocky planets are much smaller in size and the gaseous planets are larger. One theory for this is that when the Sun turned on and became a star, it caused the gas clouds of the four inner planets to blow away. The rocky planets were left with a smaller, solid planet. The gaseous planets are farther from the sun, so they retained their composition. As they increased in mass, their gravity increased which allowed them to attract more and more material from space and grow larger in size.

Sizes and Distances of Planets

The image below shows the huge variance in size between planets in our solar system. Notice the differences in size between the inner, rocky planets and the outer, gaseous planets.

“Size planets comparison” by Lsmpascal-Own work is licensed under CC BY-SA 3.0/labels added from original

Measurements of Our Solar System

Element

Diameter (km)

Distance from the Sun (x10^6) (km)

Sun

1,392,000

————————–

Mercury

4,897

57.9

Venus

12,104

108.2

Earth

12,756

149.6

Mars

6,794

227.9

Jupiter

142,980

778.6

Saturn

120,540

1433.5

Uranus

51,120

2872.5

Neptune

49,530

4495.1

A YouTube element has been excluded from this version of the text. You can view it online here: https://pressbooks.uiowa.edu/methodsii/?p=40

Why is Pluto Not a Planet?

Pluto was the ninth planet in our solar system until a controversial 2006 decision when it was reclassified as a dwarf planet. Pluto meets two requirements to be a planet: it orbits around the sun and its gravity formed the planet into a round shape. However, it does not meet the third requirement of “clearing the neighborhood.” Planets must have gravitational dominance and clear the neighborhood around their orbit; this means that large planets (more mass=more gravity) either attract or eject other, smaller bodies from that region of space. Several other dwarf planets and similarly-sized space objects were discovered in the solar system near Pluto’s orbit in the Kuiper Belt. Therefore, Pluto has not cleared the neighborhood and so it cannot be considered a planet.

Asteroids

During the early life of our solar system, dust and rocks in space were pulled together by gravity to form the planets. Not all the dust and rocks were made into planets; smaller, rocky remnants called asteroids remain and orbit the Sun in our solar system. Between Mars and Jupiter, you can find the Main Asteroid Belt which is where most of the known asteroids orbit.

Other Objects in the Solar System

- Comet: A frozen ball of gas, rock, and dust that orbit the Sun. When a comet gets close to the Sun, it heats up and the gas and dust form a tail.

- Meteor: A small rock in space that orbits around the Sun. Most meteors have broken off of larger objects such as asteroids or comets. They can be as small as a grain of sand or as large as a pickup truck.

- Meteoroid: The streak of light that is caused when a meteoroid enters Earth’s atmosphere and burns up due to friction. Also known as a shooting star.

- Meteorite: A meteoroid that survives its trip through the atmosphere and lands somewhere on Earth. The impact of a meteorite can cause a crater on the surface of a planet.

Image of Halley’s Comet by NASA is public domain

Meteorite found in the Nubian Desert in northern Sudan by NASA

4

Origins and the Universe

This timeline shows the key events in the formation of the universe. Each event is explained in more detail in this chapter.

The Big Bang

The Big Bang is the best-supported scientific theory for how the universe was created. 13.7 billion years ago there was nothing and nowhere. Everything that ever existed was contained in a subatomic particle that was billions of times smaller than an atom. Within a fraction of a second, this amazingly tiny particle stretched and inflated to an unimaginably huge size. Space, time, and the fundamental particles of the universe were created in this instant.

Key Takeaway

Although the word “bang” is part of the name, the Big Bang was an expansion or an inflation rather than an explosion.

Although there are alternate theories, the Big Bang theory is supported by multiple sources of scientific evidence.

1. Edwin Hubble discovered that the universe is still expanding today. If it is constantly expanding and growing now, that means it was smaller before–and likely the size of an unimaginably small particle at the beginning.

2. Scientists detected Cosmic Microwave Background, a type of radiation that is present everywhere in the universe. Evidence suggests that this is leftover radiation from the energy of the Big Bang.

For more explanation of the Big Bang theory, watch the following video.

A YouTube element has been excluded from this version of the text. You can view it online here: https://pressbooks.uiowa.edu/methodsii/?p=42

Video credit: “Big Bang Introduction” by Khan Academy is licensed under CC BY-NC-SA 3.0. Note: All Khan Academy content is available for free at khanacademy.org.

The Life Cycle of Stars

All stars begin their lives as clouds of gas and dust which are called nebulae. The particles in a nebula start to attract, so their combined mass increases. Therefore, they have more gravity which pulls in even more particles. Eventually, there will be enough particles under intense heat and pressure in the center core and nuclear fusion can occur. The star ignites and becomes a fully functioning star.

The image, below, shows the life cycles of different types of stars.

Life Cycle of Stars “Universal Element Formation” by Science Learning Hub-Pokapū Akoranga Pūtaiao, University of Waikato

Depending on the amount of material in the nebula, an average star (like the Sun) or a supermassive star is formed. As the star burns through its fuel, it loses mass; therefore, it has less gravity and its size increases. An average star turns into a red giant. As it continues burning fuel, the red giant becomes very large. Then, the outer layers are blown off creating a planetary nebula and the inner core of the star remains, called a white dwarf star.

A supermassive star turns into a super red giant. These stars have more mass so they burn through their fuel more quickly, therefore losing gravity and becoming extremely large. Eventually, the super red giant will run out of fuel, collapse in on itself, and create a giant explosion called a supernova. From there, the star can either form a black hole or an extremely compact neutron star.

Interesting Fact: We Are Made of Stardust

- Nuclear fusion in stars begins with hydrogen atoms which fuse together to make helium. Eventually, the reactions increase and atoms continue fusing into different elements; stars can fuse all of the elements up to iron on the periodic table.

- When the dust and debris from a star is blown away in a planetary nebula or supernova, all of these elements scatter into space where they will become the basis for all new stars and matter in the universe. Therefore, we are made of stardust.

Galaxies

A galaxy is a collection of billions of stars, gas, and dust held together by gravity in space. Using the Hubble Space Telescope, scientists can take images of space. In one small area, called the eXtreme Deep Field or XDF (image below) each of the bright spots is an entire galaxy–there are 5,550 galaxies within the image.

“Hubble eXtreme Deep Field” by NASA

For comparison, the area in the image is much smaller than the size of our Moon (image below). There are probably 100 hundred billion galaxies in the entire universe.

Image credit: “Size of Hubble eXtreme Deep Field on the Sky” by NASA

As seen in the image, below, there are 3 shapes of galaxies: spiral, elliptical, and irregular. Our galaxy, the Milky Way, is a spiral galaxy. Most galaxies have a supermassive black hole at the center which has an extremely strong gravitational pull that holds the entire galaxy together.

“Galaxies” by NASA

Black Holes

A black hole is an area in space with extremely strong gravity from which no light can escape. Thus, the area appears black. At the end of its lifecycle, a supermassive star collapses in on itself which causes a huge explosion called a supernova; this results in the formation of a black hole.

Seen below, scientists captured the first image of a black hole in 2019 using powerful telescopes.  Since black holes trap all light inside, the dark spot in the center of the image is the black hole’s shadow surrounded by a ring of glowing gas in space. Based on this image, scientists were able to determine that the this black hole’s mass is 6.5 billion times larger than the mass of our Sun.

“Black Hole” by Event Horizon Telescope is licensed under CC BY 4.0

For more explanation of black holes, watch the following video.

A YouTube element has been excluded from this version of the text. You can view it online here: https://pressbooks.uiowa.edu/methodsii/?p=42

Video credit: “What is a Black Hole?” by NASA Space Place

Origins of the Sun, Earth, and Moon

Our solar system was most likely formed from a giant rotating nebula after a former star underwent a supernova. 4.65 billion years ago, this rotation and intense gravity caused the nebula to collapse on itself. This caused it to spin faster and flatten into a disk shape, the Plane of the Ecliptic. Much of this material was pulled toward the center of the disk and a star was formed: the Sun. The Sun contains 99.8% of the mass in our solar system.

Scale image of the Sun compared to the planets in our solar system “Planets and sun size comparison” by Lsmpascal-Own work is licensed under CC BY-SA 3.0

Although it is enormous compared to the size of Earth, the Sun is an average-sized star. It is mostly made of hydrogen and helium. Currently, it is halfway through its fuel supply. In around 5-6 billion years, the Sun will burn all of its fuel and become a white dwarf star.

After the Plane of the Ecliptic was formed, the planets formed from the leftover gas and dust orbiting around the Sun. One theory says that when the Sun turned on and became a star, the force of its energy blew off the gas clouds around the four inner planets which is why they are rocky and the outer planets are gaseous. Earth, a rocky planet, is about 4.65 billion years old. Scientists believe that life on Earth appeared approximately 3.5 billion years ago, based on evidence found in fossils.

Key Takeaway

Earth was NOT formed during the Big Bang.

- The Big Bang occurred 13.7 billion years ago.

- Earth was formed 4.65 billion years ago.

- This means there is a lapse of 9 billion years between the Big Bang and the formation of Earth.

The Moon was formed when a Mars-sized object named Theia collided with the Earth. Early in its creation, Earth was molten. When it collided with Theia, chunks of Earth’s crust were ejected into space. Gravity bounded these pieces together and the Moon was formed, eventually cooling and hardening into its current rocky state. Evidence which supports this theory include that the Moon and Earth have very similar composition including an iron core, mantle, and crust, although the Moon is less dense since it was formed from lighter elements in Earth’s crust. The Moon is held to Earth by gravity and it is Earth’s only natural satellite object, although the distance between them is increasing by about 1.6 inches per year.

5

Space Science Practice Quiz

Follow this link to take the space science practice quiz. You will get immediate feedback on your answers.

“Hubble eXtreme Deep Field” by NASA

Welcome to Earth Science. This part is divided into three chapters:

1. History of Earth

2. Earth’s Structure: At the Surface and Underground

3. Rocks and the Rock Cycle

Chapters one and two will be covered on the midterm exam. Chapter three will be covered on the final exam. Additionally, there are two practice quizzes at the end.

6

History of Earth

Geologic Time

Earth was formed about 4.65 billion years ago. Scientists use the geologic time scale to describe events that have happened throughout Earth’s history.

In this image, Ma is an abbreviation for millions of years and Ga is an abbreviation for billions of years.  “Geologic Clock” by Woudlouper is public domain

If the entirety of Earth’s history was represented on a clock, humans would appear at 11:59:40 PM.

“History of Earth in a Day” by CK-12 is licensed under CC BY-NC 3.0

Origins of Life on Earth: Bacteria, Plants, and Animals

- 4.65 billion years ago: Earth is formed

- 4 billion years ago: The first life on Earth was simple, prokaryotic bacteria.

- 600 million years ago: Aquatic plants and animals evolved. It is likely that life originated in water because it offered early organisms more temperature stability compared to land, currents provided early movement, and they didn’t have to fight gravity.

- 500 million years ago: Huge period of evolution and diversification of life known as the Cambrian Period.

- 400 million years ago: Terrestrial plants and animals evolved.

- 65-250 million years ago: Dinosaurs lived during the Mesozoic Era.

- 200,00-300,000 years ago: Homo sapiens, early ancestors of humans, evolved.

Snowball Earth

At least three times in Earth’s history, the planet was engulfed almost entirely in ice–an event called Snowball Earth. These events happened between 580 and 750 million years ago. Evidence for Snowball Earth comes from sedimentary rocks. In a normal ice age, the types of rock deposited by glaciers would be found mostly near Earth’s poles. However, geologists found glacial rocks of similar ages around the world, at both the poles and equatorial regions. This led to the Snowball Earth theory.

“Snowball Earth” by NASA is public domain.

Snowball Earth was caused by a chain of events called a positive feedback loop. Ice has a high albedo and is very insulating, so it is not heated up efficiently by sunlight. As ice accumulated on the planet, it increasingly reflected more sunlight and cooled Earth even further. Thus, this created a cycle of ice formation, increased albedo, and cooling of Earth which continued until the entire planet was covered in ice.

“Positive Feedback Mechanism” by David Bice/Penn State College of Earth and Mineral Sciences is licensed under CC BY-NC-SA 4.0

Why is Earth not covered in ice now if the positive feedback loop continues forever? The leading theory is that volcanoes continued erupting during Snowball Earth, emitting high levels of carbon dioxide, which was trapped under the ice. Eventually, the carbon dioxide built up enough to start melting the ice. Ice turned to water, which has a lower albedo and thus absorbed more of the Sun’s energy. This led to a new positive feedback loop that resulted in warming of the planet and the end of Snowball Earth. Additionally, it is believed that bacterial life on Earth survived the harsh conditions during Snowball Earth events by living near the heat sources from volcanoes.

“Positive Feedback Mechanism” by David Bice/Penn State College of Earth and Mineral Sciences is licensed under CC BY-NC-SA 4.0

Pangaea

Due to plate tectonics, Earth’s land is constantly shifting and changing over time. 250 million years ago, all of Earth’s landmass was united in a single supercontinent called Pangaea. About 200 million years ago, this supercontinent began to break up into pieces as the plates moved away from each other. Smaller landmasses were formed until, eventually, the continents we recognize today were shaped. It is easy to see how certain continents, like South America and Africa, once fit together. Even today, the location of the continents continues to fluctuate. Scientists theorize that a new supercontinent, called Pangaea Proxima, could form 250 million years in the future.

“Pangaea to Present” by USGS is public domain.

Continental Drift

Proposed by scientist Alfred Wegener, the theory of continental drift was one of the earliest ways to explain why continents moved over time. Wegener noticed that the shape of Earth’s continents, such as South America and Africa, could fit together like a jigsaw puzzle. He also studied fossils from different continents that showed the remains of identical plants and animals spread throughout the world. For example, dinosaurs lived during the Triassic, Jurassic, and Cretaceous periods. As Pangaea broke into different pieces, fossils show that dinosaurs spread to different continents and evolved into different species over time. Based on this evidence, Wegener theorized that all of Earth’s continents were originally united in the supercontinent Pangaea. Over time, they drifted apart to their current positions.

“Continental Drift” by USGS is public domain

While parts of this theory were correct, Wegener’s ideas had some flaws. For example, Wegener was unable to explain how the continents had separated over time. Consequently, this theory was replaced by the plate tectonics theory which is discussed in the next chapter, “Earth’s Structure: At the Surface and Underground”.

Animation of continental drift “Pangaea Animation” by USGS is public domain

Key Takeaways

Timeline of Earth’s History:

**Change so dinosaurs come before humans, I put the stuff about plants and animals in a purple box above…so then this timeline can kind of be the summary from the whole chapter.

7

Earth’s Structure: At the Surface and Underground

Layers of Earth

“Earth’s Layers” by NASA Space Place

Earth is made up of four layers. The outermost layer is called the crust. The crust is made up rocks such as basalt and granite and it is very thin in comparison to the other layers. The crust is broken into many pieces called plates. There are two types of plates: continental plates and oceanic plates. Continental plates are much thicker than oceanic plates. Picture the depth of the ocean floor compared to the land; the ocean floor is much far below the land and, therefore, oceanic plates are thinner than continental plates.

The next layer is the mantle which is between the crust and core. This is the largest and thickest layer of Earth. The upper part of the mantle is made of magma; the tectonic plates float on this layer which is how they move.

Finally, Earth’s core is made of two layers: the outer and inner core. The liquid outer core is mostly made of iron and nickel. It is incredibly hot, so the metals remain in a liquid state. The flow of the liquid metals creates Earth’s magnetic field which is why compasses always point north. Additionally, the magnetic field protects the planet from extreme weather and radiation in space. The solid inner core is also made of iron and nickel. However, this layer is solid because the materials are under intense pressure at the center of Earth. Scientists know that the inner core is solid because of how seismic waves from earthquakes travel through the interior of Earth. The waves are unable to travel straight through the layers; instead they are refracted or bent by the dense inner core, so scientists believe this layer is solid.

A YouTube element has been excluded from this version of the text. You can view it online here: https://pressbooks.uiowa.edu/methodsii/?p=359

Video credit: “Structure of the earth” by Khan Academy is licensed under CC BY-NC-SA 3.0. Note: All Khan Academy content is available for free at khanacademy.org.

Plate Tectonics

Plate tectonics explains how Earth’s plates move. Earth’s crust is divided into many plates which float on the molten upper layer of the mantle. This area is called the lithosphere. The movement of the plates is driven by convection currents in the mantle. Heat rises from the mantle and cools as it gets closer to the surface; from there, it sinks down where it is reheated and the cycle repeats. This creates a current that moves the plates. Although they are constantly moving, each plate moves very slowly–about 3 to 5 centimeters (1 to 2 inches) per year.

Tectonic Plate Boundaries

There are three types of tectonic plate boundaries:

1. Transform boundary: plates sideswipe each other

2. Divergent boundary: plates pull apart from each other

3. Convergent boundary: plates push into each other

Transform, divergent, and convergent plate boundaries. “Plate tectonics” by USGS is public domain.

Depending on the type of tectonic plate and the type of plate boundary, different landforms can occur along plate boundaries.

- Convergent plates:

- When two continental plates converge, the land is pushed into each other and upward forming a mountain.

- When two oceanic plates converge, one plate is subducted under the other. In this situation, a trench or an island arc is formed.

- When a continental plate converges with an oceanic plate, the denser oceanic plate is subducted under the continental plate. As the oceanic plate is forced deeper underground, it reaches very high temperatures and melts into magma. Then, magma can rise up into the space and form volcanoes. This can also form a mountain range; for examples, the Andes mountains were formed in this way.

- Divergent plates

- In the ocean, magma rises up to fill the space between plates and a volcano is formed. When the material from the volcanic eruptions builds up over time, it forms a mid-ocean ridge.

- On land, a rift valley, or large crack is formed.

“Tectonic Plate Boundaries” by Jose F. Vigil/USGS is part of the public domain

As seen in the map below, the Ring of Fire is an area in the Pacific Ocean bounded by several tectonic plates. Most of Earth’s earthquakes and volcanoes occur in this area due to the shifting of tectonic plates along these boundaries.

“Map of Tectonic Plates” by NOAA is part of the public domain

Volcanoes

A volcano is a vent that allows magma, rock fragments, ash, and gases to escape to the surface of a planet or moon. Volcanoes have created more than 80% of Earth’s surface. Volcanoes are found on every continent and on the sea floor in Earth’s oceans, as well as on several planets and moons in space.

When the material (magma, ash, and gases) from a volcano comes to Earth’s surface, it is called an eruption. There are two different types of volcanic eruptions: explosive and effusive. Explosive eruptions are when the magma is fiercely fragmented and rapidly expelled from a volcano. Effusive eruptions are when lava steadily flows out a volcano onto the ground.

Effusive Eruptions

- lava steadily flows out a volcano onto the ground

- occurs when magmas reaches the surface

- builds up gentle sloping shield volcanoes

“Effusive eruption” by Michael Ryan/USGS is public domain

Explosive Eruptions

- the magma is fiercely fragmented and rapidly expelled

- occurs where cooler magmas reaches the surface

- builds up steep sloping composite volcanoes

“Explosive eruption” by Mike Doukas/USGS is public domain

How Volcanoes are Formed

Volcanoes form when magma from deep within Earth rises to the surface. Volcanoes can be formed in 3 ways: converging tectonic plates, diverging tectonic plates, or over a hot spot.

- Convergent plates

When an oceanic plate converges with a continental plate, the oceanic plate subducts under the continental plate forming a subduction zone. At this zone, the denser plate is pushed under the other and the rock melts under intense heat and pressure as it is pushed further into Earth. Thus, the melted rock turns to magma and is able to rise to Earth’s surface as a volcano.

- Divergent plates

When two plates diverge, magma rises up to fill the space in between and an underwater volcano forms.

- Hot spots

A hot spot is an extremely hot area in the mantle where magma can rise up to the surface and create volcanic activity. The heat comes from deep within Earth, melting rock at the crust and forming magma. More typically, volcanoes occur along plate boundaries, but hot spots are located in the middle of tectonic plates. Yellowstone National Park in Wyoming is a supervolcano located over a hot spot. It hasn’t erupted for 174,000 years and is not expected to erupt soon. However, features in the park such as the geyser Old Faithful are fueled by volcanic activity over the hot spot.

“Volcano formation” by NASA Space Place

The Hawaiian Islands, an island arc, were also formed by hot spot volcanoes on the Pacific Plate. The Pacific Plate is slowly moving northwest over time while the hot spot stays in the same place. As such, different areas of the plate are located over the hot spot at different times. Material from underwater volcanic eruptions at the hot spot builds up until it eventually reaches the surface, forming an island.

Based on the ages of rocks found on the islands, scientists can determine that the westernmost island, Kauai, is the oldest. 5 million years ago, Kauai was located over the hot spot. As the Pacific Plate shifted west, new islands in the chain were formed. Therefore, the easternmost island, the Big Island, is the youngest island and it is currently located over the hot spot. Eventually, new islands will continue to form in Hawaii. Scientists have detected a the beginnings of a new island, named Loihi, located southwest of the Big Island. Although it is currently located far below the ocean surface, volcanic eruptions have started to form Loihi and it will reach the surface in tens of thousands of years.

A YouTube element has been excluded from this version of the text. You can view it online here: https://pressbooks.uiowa.edu/methodsii/?p=359

Video credit: “Hawaiian Islands Formation” by Khan Academy is licensed under CC BY-NC-SA 3.0. Note: All Khan Academy content is available for free at khanacademy.org.

Earthquakes

Tectonic plates float on the mantle, the layer below the crust. Breaks in the rock of the plates are called faults; these can occur in the form of plate boundaries as well as smaller cracks on the interior of plates. The rock moves along these fault lines at transform boundaries. Sometimes, however, they are unable to easily pass. The plates continue to push into or slide past each other which causes intense stress to build up. Eventually, the rocks will snap and the pressure will be released in the form of powerful seismic waves. This causes the ground to shake–an earthquake.

Law of Superposition

The Law of Superposition states that deeper layers of rock are older; deeper layers of rock were formed before layers that are closer to the surface. The Law of Original Horizontality states that successive layers of rock are formed in flat, horizontal layers; this is because gravity pulls down on the rock when it forms. Using these laws, geologists and archaeologists can determine the relative age the layers of rocks.

Sometimes, however, layers of rock do not match up horizontally. Due to the movement of Earth’s plates, the layers constantly shift and may become skewed or tilted. Additionally, surface level factors such as erosion and weathering can affect the top layer of earth by washing parts of it away. Finally, intrusions of magma (which forms igneous rock) can disrupt the horizontal layers beneath the surface. All of these factors provide clues for scientists to understand what occurred and when it happened at different times on Earth.

“Laws of Superposition and Original Horizontality” by CK-12 is licensed under CC BY-NC 3.0

In the image, above, the layers of rock oldest to youngest are C, B, A, D.

- C is the oldest because it is the deepest layer.

- Next, B was formed on top of C.

- Then, A was formed on top of B.

- D is an intrusion of magma. We can tell it happened after A, B, and C were formed because it intrudes through all three layers and reaches the surface of Earth.

- Finally, a shift occurred in the layers due to plate tectonics, represented by the line, E. We can tell this happened last because every layer of rock and the intrusion have been disrupted and they are skewed horizontally.

To learn more about the Law of Superposition, the following video is highly-recommended viewing:

A YouTube element has been excluded from this version of the text. You can view it online here: https://pressbooks.uiowa.edu/methodsii/?p=359

Video credit: Law of Superposition by Bozeman Science is licensed under CC BY 3.0

Fossils

Fossils are the remains of plants or animals that have been preserved in rock. Fossils form when the remains of a plant or animal are quickly buried after they die. Over time, the remains are replaced by minerals and compacted between layers of sediment to form fossils in sedimentary rock. Fossils are very fragile so they can only be found in sedimentary rocks; the extreme heat and pressure needed to form igneous and metamorphic rocks would destroy the fossil.

Fossils can also tell a story. Using the Laws of Superposition and Original Horizontality, geologists can figure out the relative age of a certain layer of rock. Sometimes, a specific type of fossil is found widely throughout one of these horizontal layers. Scientists can infer, then, that the organism lived during the same geologic time; this is called an index fossil. If the same type of fossil is found in other areas of rock, scientists can figure out that certain layers of rock were formed at the same time as well. In this way, fossils are a record of geologic time that tell a story to the people who find them.

Disciplinary Core Ideas

ESS1.C: The History of Planet Earth

- Local, regional, and global patterns of rock formations reveal changes over time due to earth forces, such as earthquakes. The presence and location of certain fossil types indicate the order in which rock layers were formed.

8

Practice Quiz (Midterm Earth Information)

Follow this link to take the earth science midterm quiz. The information on this quiz will be on the midterm exam. You will get immediate feedback on your answers.

“Hawaii Volcano Eruption” by USGS is public domain

9

Rocks and the Rock Cycle

Types of Rocks

Rocks are classified as three types: Igneous, Sedimentary, and Metamorphic.

Igneous

Sedimentary

Metamorphic

- formed when magma cools

- formed when many small particles called sediments are compacted together over time

- formed when existing rocks undergo extreme heat and pressure

- The early Earth was made of liquid magma that then cooled to form solid rocks, so this was the first type of rock.

- Fossils are always found in sedimentary rocks.

- The word metamorphic means to transform or change shape; you may have heard the term metamorphosis–the process in which a caterpillar transforms into a butterfly.

Intrusive Igneous Rocks

Extrusive Igneous Rocks

When magma cools underground, it cools more slowly. Since it is inside Earth, it is well protected and forms larger crystals. This is called an intrusive rock.

When magma cools in water or on the surface of Earth, like after a volcano erupts, it cools more quickly and forms smaller crystals. This is called an extrusive rock.

Rock Cycle

The key processes in the rock cycle are heat & pressure and weathering & erosion. Each type of rock can undergo different changes that affect its form and the type of rock it is.

Igneous rocks:

- Can undergo heat and pressure to become a metamorphic rock

- Can undergo weathering and erosion to become a sedimentary rock

- Can melt and become magma again. Then, it will cool and re-form as an igneous rock.

Sedimentary rocks:

- Can undergo heat and pressure to become a metamorphic rock

- Can undergo weathering and erosion, thereby breaking apart into sediments. Then, these sediments can be compacted again into sedimentary rocks.

- Can melt and become magma or igneous rock

Metamorphic rocks:

- Can undergo heat and pressure to transform into another metamorphic rock

- Can undergo weathering and erosion to become a sedimentary rock

- Can melt and become magma and igneous rock

“The Rock Cycle“
Copyright © 1999-2003, Wheeling Jesuit University/Center for Educational Technologies®. All rights reserved. Full copyright statement found here.

Geodes

A geode forms when a cavity forms in a rock, which can occur in different ways. One way a cavity can form occurs when a bubble of carbon dioxide and water vapor forms in flowing lava. As the molten rock cools and the gas dissolves, an empty space is left behind. Another possibility in which a cavity can form occurs when lava solidifies under water. Sometimes the outside of the melted rock cools before the inside, which becomes brittle and breaks a little bit due to the weight of the liquid inside. That liquid then leaks out, leaving a hollow space and a crack for minerals to seep into overtime. Cavities that allow geodes to form are most commonly found in igneous rock formed by cooling lava or magma.

However, cavities can also form in sedimentary rocks, such as limestone and sandstone. In these particular rocks, the cavity generally forms a solid core. In some cases, in the sediment, a mass of minerals begin to dissolve and leave behind space. In other cases, organic material, like a piece of wood, gets buried in the sediment and eventually weathers over time, leaving behind empty space. Once these rocks are hollow, or at least semi-hollow, various minerals are able to seep in through the rock’s microscopic pores, creating crystalline structures over long periods of time. Different minerals form different types and colors of crystals inside the geodes.

Archimedes’ Principle

Archimedes’ Principle is a law of physics regarding buoyancy. The principle states, “The buoyant force applied by the fluid is equal to the weight of the displaced fluid. Essentially, when an object is immersed fully or partially in a fluid, the upward force applied by the fluid on the object is the same as the weight of the fluid displaced by the object.” We can apply Archimedes’ Principle with the equation W(air) / (w(air)-W(water)) to determine how much of the geode is solid and how much is hollow.

Key Takeaways

- W(air) / (w(air)-W(water)) = Archimedes’ Law

- This helps to find how much of the geode is solid and how much is hollow

- Weight of displaced liquid = weight of the object

Archimedes’ Principle explained (explanation of the principle technically begins around 5:54, but the additional information about fluids at rest leading up to it is helpful to have a better understanding of Archimedes’ Principle):

A YouTube element has been excluded from this version of the text. You can view it online here: https://pressbooks.uiowa.edu/methodsii/?p=361

Weathering, Erosion, and Deposition

Weathering is the breakdown of rocks on Earth’s surface. There are two types of weathering:

1. Mechanical: also known as physical weathering, rock is broken down into smaller fragments due to water, wind, or other conditions such as temperature and pressure changes

2. Chemical: chemical reactions change the molecular structure of the rock

After the rocks are broken down through weathering, erosion can occur. Erosion is the process by which the small bits of rock are transported to a new location. Finally, deposition occurs when the particles are added to or deposited at a new location. These three processes act as a cycle, continually breaking down and building up different parts of Earth’s landscape.

Key Takeaway

Weathering is the making the mess and Erosion is cleaning it up.

Sand

Sand is any rocky material that is bigger in size than silt and smaller than gravel. Sand is created when rocks are weathered, or broken down, in one of two ways: by water or by wind. When wind or water continually passes over a rock, it breaks it down into smaller and smaller pieces and sand is formed. Sand that was formed from weathering by wind tends to be pitted and frosted in appearance because other grains of sand have constantly been pelted against the rock. Sand that was formed from weathering by water tends to be smooth and polished because the water has continually passed over the rock.

Where did this sand come from?

Type of Sand

Location

Characteristics

Weathering by wind

Dunes in the desert

Scratched or frosted, pitted, uniform in size

Weathering by water

Rocks near water

Rounded, polished, smooth

Like fossils, sand can also tell a story. Based on where it is found in the world, sand is composed of different materials. Thus, it can also come in a variety of colors such as black, white, green, red and pink. Black sand, for example, is made from lava that has cooled to form an igneous rock; one place it can be found is near volcanoes in Hawaii.

“Hawaii Black Sand Beach” by Ryan Keene is licensed under CC BY-NC-ND 2.0

10

Practice Quiz (Final Exam Earth Information)

Follow this link to take the earth science final quiz. The information on this quiz will be on the final exam. You will get immediate feedback on your answers.

“Sand Under a Microscope“

11

Climate vs. Weather

Weather vs. Climate

Weather is the short-term atmospheric conditions in an area like, “It’s raining” or “It’s sunny today”. As such, weather can change day to day.

Climate is the usual weather activity that can be expected for an area and time of year such as, “Minnesota is so snowy during the winter” or “Florida is sunny in the summer”. Climate is measured in 30-year intervals, so the term climate change refers to the continual change of the climate over time from what is typically expected to happen.

Some people confuse weather and climate. For example, you may hear something like, “This snowstorm is crazy…we need global warming!” However, this statement confuses weather and climate. A snowstorm that lasts for a few days is a weather event; global warming is part of climate change which is measured over decades. Earth could have its hottest day on record–a weather event–but we cannot call that climate change unless a trend indicating a change in temperature can be measured over a 30-year period.

Key Takeaways

- Weather: what is happening NOW

- Climate: what happens USUALLY

What factors determine whether an area has a hot or cold climate?

L.O.W.E.R. Near Water

- L: Latitude

- Latitudes near the Equator have warmer temperatures.

- Latitudes near the North and South poles have colder temperatures.

- O: Ocean currents

- The temperature of an ocean current affects the temperature of the air that passes over it.

- Example: The California Current brings cooler air from north to south; therefore, California’s coastal cities tend to have a cooler climate. Conversely, the Gulf Stream carries warmer air from tropical areas to the southeastern United States; therefore, this region tends to have a warmer climate.

On this map, you can see the cold California Current (#6) that carries cold air to the west coast and the warm Gulf Stream (#1) that carries warm air to the east coast. “Global Conveyer Belt” by Heinrich-Böll-Stiftung is licensed under CC BY 2.0

- W: Wind and air masses

- Air masses take on the climatic conditions of the area where they are formed. When wind moves these air masses to a new area, they bring the climatic conditions with them which can affect the weather and climate of the new location.

- Example: If the wind or air mass is coming from the Arctic, it will bring colder air to an area. If the wind or air mass is coming from the tropics, it will bring warmer air to an area.

- E: Elevation

- Higher altitudes tend to be cooler, while lower altitudes tend to be warmer. This is because there is less pressure at higher altitudes, so the air expands and cools.

- R: Relief (aka topography)

- When an air mass rises to pass over topography such as a mountain, it expands and cools. This causes precipitation on that side of the mountain. A rain shadow is created because the precipitation cannot pass over the mountain to the other side.

“Rain Shadow” by NPS is public domain

- Example: The Sierra Nevada mountain range in California is a topographical feature that affects climate. West of the mountains, moist air comes off the Pacific Ocean. As this air rises to go up the mountains, precipitation occurs; San Francisco, a city west of the Sierra Nevada, is known for having a cool and wet climate. On the other side of the mountain, precipitation is blocked and the area becomes a desert known as a rain shadow; Death Valley, one of the hottest and driest places in the world is located east of the Sierra Nevada.

- Near Water:

- In the summer, water acts like an air conditioner to keep the air temperatures cool. In the winter, water acts like a heater to keep the temperatures from getting too cool.

- Continental climate=far from water; maritime climate=near water.

- Example: As seen in the map below, Ontario, Canada–an inland province–has a moderate climate due to its proximity to the Great Lakes. Ontario is cooler in the summer and warmer in the winter than other areas at the same latitude due to the effects of the Great Lakes.

“Map of Canada” by E Pluribus Anthony is public domain

12

Climate: Background Information

Climate is what happens USUALLY

Earth’s Atmosphere

Earth’s atmosphere is a layer of gases, mainly nitrogen and oxygen, between Earth’s surface and space. From space, the atmosphere can be seen as a thin blue line around Earth’s circumference in the image below.

“The Atmosphere” by NASA is public domain

The atmosphere is relatively thin, 60 miles wide, but it plays an important role for the planet. It lets in heat from the Sun so Earth has a livable temperature, while also acting a shield to block much of the Sun’s harmful radiation. When Earth’s systems are in balance, the atmosphere is a key part of regulating temperature, weather, and climate.

What is a greenhouse gas?

Certain gases in Earth’s atmosphere are called greenhouse gases. Like a greenhouse, they let sunlight through to reach the surface of Earth and then trap its heat in the atmosphere. The most abundant greenhouse gases are:

- Carbon dioxide (CO2)-Carbon dioxide is naturally released from decaying organisms and volcanic eruptions. However, humans are the main cause of excess carbon dioxide in the atmosphere from burning fossil fuels.

- Nitrous oxide (N_2O)-Bacteria naturally produce nitrous oxide, but humans create more from industrial activities such as factory waste and agricultural products such as fertilizer.

- Methane (CH4)-Methane is naturally created in wetlands and oceans, but humans also contribute to excess methane through agriculture; cows release a significant amount of methane by burping when they digest their food.

- Water Vapor (H_2O)-From the effects of climate change, there is more energy in Earth’s systems and the global water cycle. As the temperature increases, this causes more water to evaporate and enter the atmosphere as water vapor, a heat-trapping molecule.

- Ozone (O_3)-High in the atmosphere, the ozone layer (naturally occurring ozone) blocks the Sun’s radiation and helps regulate Earth’s temperature. Lower in the atmosphere, however, human activities such as vehicle emissions create additional ozone. This ozone is bad because it traps heat in the atmosphere and creates smog.

“Greenhouse Gases” by NASA Space Place is public domain

Greenhouse gases are complex molecules made of three or more atoms bonded together. Gases move quickly and collide with other molecules in the atmosphere. This causes greenhouse gas molecules to vibrate and have an asymmetrical shape.

Because of this asymmetrical shape, they can absorb infrared radiation from the Sun. Then, the radiation is released back into the atmosphere which helps keep the planet warm enough to support life. Other gases in Earth’s atmosphere such as nitrogen and oxygen are more abundant, but they do not absorb infrared radiation because their molecular structure stays symmetrical.

The Greenhouse Effect

Watch the following video for a short explanation of carbon dioxide and the greenhouse effect.

A YouTube element has been excluded from this version of the text. You can view it online here: https://pressbooks.uiowa.edu/methodsii/?p=613

Video Credit: “Earth’s Gas Problem” by NASA Global Climate Change is public domain

What is the greenhouse effect?

The greenhouse effect describes how greenhouse gases in Earth’s atmosphere trap heat.

When infrared radiation from the Sun reaches Earth:

- Some radiation is reflected back into space by the atmosphere and surfaces with a high albedo such as ice.

- Other radiation is absorbed by greenhouse gases and surfaces with a low albedo such as land and water.

- Absorbed radiation is later released as heat which increases Earth’s temperature.

Watch the animation, below, to see the greenhouse effect in action.

“The Greenhouse Effect” by NASA is public domain

The greenhouse effect is a key part of Earth’s natural processes. Without heat from the Sun’s radiation and the atmosphere’s protection, Earth’s temperature would not be regulated to support life. However, the greenhouse effect can go too far when Earth’s systems are out of balance.

Earth’s atmosphere can be compared to a blanket that is wrapped around the planet; the planet needs this blanket to survive in outer space. But when there are too many greenhouse gases in the atmosphere (from burning fossil fuels, for example), they radiate more heat than normal. This causes Earth’s blanket to get thicker and thicker and global temperature increases. Unfortunately, Earth cannot simply take the blanket off in order to cool down. Over time, this leads to our current situation: global climate change with wide-reaching and serious consequences.

Albedo Effect

Albedo is the amount of energy reflected by a surface. Light surfaces tend to have a high albedo because they reflect more energy. Dark surfaces tend to have a low albedo because they absorb more energy.

As seen in the image, below, the Sun’s rays project solar radiation to Earth’s surface. Lighter-colored surfaces such as ice reflect the radiation. Darker-colored surfaces such as land and water absorb the Sun’s heat.

“Albedo” by NASA is public domain

Currently, Earth’s albedo is decreasing as a result of climate change. As ice melts at the poles and glaciers, it is replaced by land and water. Because of their darker colors, land and water have low albedo–they absorb radiation which increases Earth’s temperature and leads to increased ice melt. This relationship, a positive feedback loop, is shown in the image below.

“Positive Feedback Mechanism” by David Bice/Penn State College of Earth and Mineral Sciences is licensed under CC BY-NC-SA 4.0

Key Takeaways

- Darker materials absorb heat–low albedo

- Lighter materials reflect heat–high albedo

“Albedo” by NASA is public domain

The Carbon Cycle

Carbon is an abundant element that is critical for life on Earth. As seen in the image, below, carbon naturally moves between the atmosphere, land, and water in the carbon cycle. Most of Earth’s carbon is stored in rocks and sediments, but also in the oceans and in the atmosphere.

“Carbon Cycle” by NOAA is public domain

Carbon dioxide, a greenhouse gas, is important for life on Earth. For example, it traps heat to regulate Earth’s temperature and is a key component of photosynthesis, the process by which plants create their own food. Due to human activities, however, carbon dioxide is increasing to abnormally high levels in the atmosphere and causing Earth’s temperature to heat up.

The following video shows the global carbon cycle, how carbon dioxide in Earth’s atmosphere fluctuates and moves around the globe over the course of a year.

A YouTube element has been excluded from this version of the text. You can view it online here: https://pressbooks.uiowa.edu/methodsii/?p=613

Video Credit: “A Year in the Life of Earth’s CO2” by NASA is public domain

What is ppm?

Carbon dioxide in the atmosphere is measured in parts per million (ppm).

So, if the CO_2 concentration is 400 ppm, that means 400 molecules out of every one million gas molecules in the atmosphere are carbon dioxide.

Scientists use ice cores, samples of ice drilled from ice sheets and glaciers, to gather data about carbon dioxide levels over time. The Law of Superposition and the Law of Original Horizontality can be applied to ice cores as well: Older layers of ice are compacted and trapped beneath newer layers over time. Within each layer, bubbles of carbon dioxide are trapped; this provides scientists with a record of atmospheric levels of carbon dioxide going back hundreds of thousands of years. Scientists can also use this data to create climate models which help predict future climate change.

“Ice Core” by Ludovic Brucker/NASA Goddard Space Flight Center is public domain

The graph, below, was created using ice core data. As shown in the graph, carbon dioxide levels on Earth have naturally fluctuated for hundreds of thousands of years. Still, CO_2 levels were relatively stable within a certain range and never exceeded 300 ppm.

At the far right side of the graph, there is a sharp uptick in CO_2 levels, indicating the rise of fossil fuel use. By 2017, the average was 405 ppm. NASA’s most recent data from July 2019 measured 411 ppm of CO_2 in the atmosphere. All of this data indicates that Earth’s systems are out of balance from typical patterns that have been established over millennia.

“CO2 Graph” by NOAA Climate.gov is public domain

13

Climate Change

Climate Change

According to a recent report from scientists at the National Oceanic and Atmospheric Administration (NOAA):

Click hereto read the full report: NOAA. (2019). July 2019 was the hottest month on record for the planet. Retrieved from https://www.noaa.gov/news/july-2019-was-hottest-month-on-record-for-planet

Fast Facts:

- Since record keeping began in 1880, July 2019 was the hottest month on record.

- Year-to-date, January to July 2019 was the second-hottest time period on record with temperatures 1.71 degrees F higher than average globally.

- Arctic and Antarctic sea ice levels were both at record lows for the month of July.

At the most basic level, climate change is a significant change over a 30-year period from the typical or expected weather patterns of an area. Earth’s climate has always fluctuated; the difference now is that Earth is experiencing significant climate change in a much shorter time period–decades rather than millions of years.

Climate change is human-caused. Since the rise of industrialization in the 19th century, humans have relied more and more on fossil fuels for energy. However, fossil fuels release a significant amount of greenhouse gases, especially carbon dioxide, into the air when they are burned. This has led to a rapid rise in global temperature as well as many other significant changes to Earth’s natural balance.

The video, below, shows Earth’s temperature increase between 1880 and 2017.

A YouTube element has been excluded from this version of the text. You can view it online here: https://pressbooks.uiowa.edu/methodsii/?p=794

Video Credit: “Global Temperature” by NASA Climate Change is public domain

Tipping Points: The Point of No Return

Human caused climate change is not a new idea.

- In 1861, scientist John Tyndall explained how greenhouse gases like carbon dioxide and water vapor absorb heat in the atmosphere.

- In 1896, scientist Svante Arrhenius built upon Tyndall’s work and predicted global warming.

- In 1956, an article published in the New York Times discussed the role of carbon dioxide in human-caused climate change (Click here to access the article).

- In 2006, Al Gore’s popular documentary An Inconvenient Truth warned the public of imminent and serious consequences of climate change.

Despite decades of warnings and scientific data, human-caused climate change has severely escalated. Atmospheric carbon dioxide has massively increased leading to higher global temperatures and a multitude of other serious consequences for the planet.

Recently, scientists have warned that we are near to reaching a tipping point, a place of irreversible damage where abnormal and extreme climate change conditions become the norm. Some climate models predict that Earth could reach a tipping point by 2060 if significant action is not taken to reduce greenhouse gas emissions and other human factors that accelerate climate change.

Global Impact of Climate Change

Due to climate change, Earth’s systems are out of balance. Global systems have more energy than normal and climate change events are often amplified by each other. This creates a positive feedback loop which has wide-ranging effects. including more extreme temperatures, more extreme weather events, melting sea ice, glacier retreat, sea level rise, and ecosystem disruption.

Watch the video, below, for a quick overview of the impacts of climate change.

A YouTube element has been excluded from this version of the text. You can view it online here: https://pressbooks.uiowa.edu/methodsii/?p=794

Video Credit: “Earth Has a Fever” by NASA Global Climate Change is public domain

More Extreme Temperatures

Climate change is not just global warming. Although Earth’s climate is heating up overall, climate change leads to increased frequency and intensity of temperature–a weather event–at both the high and low range of the spectrum.

For example, July 2019 was the hottest month on record globally. On the map, below, the pink and red shading indicates areas that had warmer than average temperatures.

“Temperature Map” by NOAA is public domain

On the other hand, climate change can also cause extreme and abnormally cold temperatures. As seen in the images below, the polar vortex–a system of freezing wind and air–split from its normal position over the Arctic in January 2019. The vortex, now unstable, caused the jet stream to warp from its normal pattern. This pushed extremely cold Arctic air down to the midwestern United States while areas of Alaska experienced warm weather. While the polar vortex is an example of weather, not climate, it is likely that the planet will experience more frequent and unexpected temperature extremes such as this due to the effects of climate change.

“Polar Vortex” by NOAA is public domain

More Extreme Weather Events

An increase in the frequency and intensity of extreme weather events is one way many people can observe and recognize climate change. The image, below, shows weather events that typically increase due to climate change. From left to right they are: heat waves, drought, hurricanes, wildfires, and melting sea ice.

“Photo Collage” by NOAA is public domain

The map, below, shows the cost per state in weather disasters causing $1 billion or more in damages between 1980 and 2019. In total, these disasters costed the U.S. more than $1.7 trillion, although different states were affected by different types of weather.

- Iowa (shaded a medium red color on the map) has experienced the most impact from drought and flood-related damages, each costing between $10-20 billion.

- Texas (shaded a dark red color on the map) has suffered the most from tropical cyclones–including Hurricanes Rita, Ike, and Harvey–with a total cost of $100-200 billion.

Click  here  to access the interactive map and see data for other states.

“Billion-Dollar Weather Events” by NOAA National Centers for Environmental Information is public domain

Melting Sea Ice

Temperatures at the North and South Poles are rising at twice the rate of the rest of the world due to melting ice and the albedo effect. This is an example of a positive feedback loop: As temperatures warm, more sea ice melts into water which absorbs solar radiation and causes temperatures to warm even further. The image, below, illustrates this positive feedback loop.

“Positive Feedback Loop” by NASA Climate Kids

The photos, below, show the Bering and Chukchi Seas which are located in the northern Pacific Ocean between Alaska and Russia. These seas typically have maximum ice cover in late March and early April; as seen in the image on the left, most of the sea is covered in ice. Just five years later, the image on the right shows significantly less ice on the sea. In fact, 2019 had the lowest levels of ice on record for this region.

“Sea Ice” by NOAA is public domain

Ice has a higher albedo than water so it reflects the Sun’s rays back into the atmosphere. When sea ice melts, darker-colored seawater absorbs the sun’s radiation which heats the oceans. Higher ocean temperatures negatively affect plants and living creatures in marine ecosystems which affects marine-based economic industries, such as fishing, in turn.

Glacier Retreat

Glaciers are large bodies of snow and ice that move slowly across land. Glaciers naturally fluctuate in size with the seasons, but climate change has led to warmer temperatures overall. This means that glaciers melt at a faster rate than snow falls to rebuild the glacier’s mass, a phenomenon called glacier retreat. Melting glaciers affects the ecosystem of an area because different plants and animals will not be able to survive in a changing landscape. Additionally, humans rely on typical ice melt from glaciers as a critical water source which dwindles when glaciers retreat.

For example, when Montana’s Glacier National Park was created in 1910, it had 150 glaciers. Today, only 26 remain and they are all significantly smaller than their original size. The image, below, shows the significant retreat of the Boulder Glacier. Today, the glacier is so small it is considered inactive. Click here to see more images of glacier retreat.

“Retreat of Boulder Glacier“. Left photo by George Grant. Right photo by Jerry DeSanto. Images courtesy of NOROCK are public domain.

Sea Level Rise

The main cause of sea level rise is thermal expansion. When water is heated, its volume increases. Picture a pot of water boiling on the stove: When the liquid water heats, it expands and turns to steam which has a larger volume.

The same thing happens with water in the ocean. As Earth’s temperature increases due to climate change, the oceans are absorbing 90% of the increased heat. As the temperature of the ocean increases, its volume increases so sea level rises.

Watch the following video for more explanation of thermal expansion.

A YouTube element has been excluded from this version of the text. You can view it online here: https://pressbooks.uiowa.edu/methodsii/?p=794

Video Credit: “The Secret to Rising Sea Levels–Thermal Expansion” by ASAP Science, video used with permission

The second cause of sea level rise is ice melt from land. As global temperatures rise, ice sheets and glaciers are melting at increasingly fast rates. However, it is important to note that only ice melt from Antarctica and other land masses contributes to sea level rise.

- Antarctica is a continent so it has land underneath the ice. When the ice melts, it runs off into the ocean. Thus, there is more water in the ocean and sea level rises.

- Ice at the North Pole floats in the ocean; it does not have land underneath. Therefore, the volume of water in the ocean stays the same and sea level does not change when Arctic ice melts.

Like Antarctica, ice melting off of Greenland contributes to sea level rise because Greenland is an island. Watch the following short video for further explanation.

A YouTube element has been excluded from this version of the text. You can view it online here: https://pressbooks.uiowa.edu/methodsii/?p=794

Video Credit: “Greenland Ice” by NASA Global Climate Change is public domain

Ecosystem Disruption

As the climate changes, the delicate balance of many ecosystems is disrupted or even destroyed. One example is coral reefs. Coral reefs play a critical role in the ocean ecosystem–they provide shelter for thousands of marine species, they regulate carbon dioxide levels in the ocean, they protect the shoreline from rough waters and storms, and they generate billions of dollars in revenue from fishing and tourism.

Coral reefs are severely impacted by climate change. Scientists estimate that more than a quarter of coral reefs have died worldwide in the last three decades. Read the infographic below to learn more about coral reefs and climate change.

“Threats to Coral Reefs” by NOAA National Ocean Service is public domain

Climate Change in Iowa  ppt 7.1

General trends from climate change in Iowa

-More rain, warmer winters, hundred-year floods

Iowa Climate Statement 2019: “Dangerous Heat Events Will Be More Frequent and Severe”

Based on data which has been peer-reviewed by thousands of scientists, researchers and educators from colleges and universities across Iowa release an annual Iowa Climate Statement each year. According to the Iowa Climate Statement 2019, “Dangerous Heat Events Will Be More Frequent and Severe”. Click here to access the one-page report.

Previous topics have included the impact of climate change on Iowa agriculture, droughts in Iowa, humidity and heat, and calls to politicians to address climate change. Click here to access previous Iowa climate statements.

Misinformation and Doubt

Among scientists, there is nearly universal consensus that human-caused climate change is occurring and it has serious ramifications for life on Earth. Nonetheless, there is still widespread misinformation and doubt about global climate change.

Politics/Economics-Resistance to climate science and data, fake news/science

What is Being Done?

Paris Climate Agreement ppt 8.2

What individuals can do

Educate yourself

14

Weather

Weather is what is happening NOW

Warm and cold fronts

A warm front is the boundary where a warmer air mass is moving in to replace a cooler air mass; the air behind a warm front is warmer than the area it is moving into.

A cold front is the boundary where a cooler air mass is moving in to replace a warmer air mass; the air behind a cold front is cooler than the area it is moving into.

Pressure systems

The air pressure on Earth changes throughout the day which affects the weather of an area. A high or low pressure system indicates higher or lower pressure than what is typical for an area. In general, air moves from high pressure areas to low pressure areas.

In a low pressure system, there is less pressure on Earth’s surface so air rises. The rising air carries water vapor into the atmosphere which forms clouds and leads to precipitation. As such, a low pressure system is associated with more volatile weather conditions such as clouds, rain, and wind.

In a high pressure system, there is more pressure on Earth’s surface so air descends. Consequently, fewer clouds form. Therefore, the weather is typically sunny and clear in a high pressure system.

How to Read a Weather Map

A red line indicates a warm front. The circles point in the direction that the front is moving.

A blue line indicates a cold front. The triangles point in the direction that the front is moving.

A line that alternates blue and red indicates a stationary front–an area where a warm and cold front meet, but neither replaces the other.

A blue H is used to indicate a high pressure system. A red L is used to indicate a low pressure system.

All weather symbols by NOAA are public domain

On the weather map, below, different symbols are used to indicate weather conditions across the United States.

“Weather Map” by NOAA is public domain

“Red sky at night, sailor’s delight. Red sky in morning, sailors take warning.”

This saying has been used to predict the weather for many years; similar sayings have even been quoted in the Bible and Shakespeare’s plays. However, this saying is also scientifically accurate.

Light from the Sun is made of all the colors of the rainbow. Picture the arc of a rainbow: The red wavelengths on the outside are longer and the blue wavelengths on the inside are shorter. On a typical day, the blue light is scattered and reflected by particles in the atmosphere most efficiently because it travels in shorter wavelengths. This is why the sky is blue.

“Blue Sky” by NASA Space Place is public domain

A high pressure system is associated with good weather. However, the air is filled with dust and aerosols because the air is pushed down closer to the surface of Earth. These particles scatter long red wavelengths through the atmosphere more efficiently than blue wavelengths which gives the sky a red appearance at sunrise and sunset.

“Red Sky” by NASA Space Place is public domain

“Red sky at night, sailor’s delight.”

In the middle latitudes, between 30 and 60 degrees, weather generally moves from west to east. The Sun sets in the west, so a red sky at night indicates that good weather will be moving toward you the next day.

“Red sky at morning, sailors take warning.”

The Sun rises in the east, so a red sky in the morning indicates that the good weather has already passed. Therefore, a low pressure system, and bad weather, will likely be moving in next.

Carbon Cycle

Within the carbon cycle, there are two interconnected subcycles. One is dealing with the rapid carbon exchange with living organisms. The other one is dealing with long-term cycling of carbon through geologic processes. In this cycle, carbon dioxide goes through make changes. Photosynthesis can convert carbon dioxide gas into organic carbon. Also, when matter from living organisms are buried deep underground, they become fossilized which is a form of long-term storage of organic carbon.

Biogeochemical cycles by OpenStax College CC by 4.0; modification of work by John M. Evans and Howard Perlman, USGS

A YouTube element has been excluded from this version of the text. You can view it online here: https://pressbooks.uiowa.edu/methodsii/?p=615

Video credit: “The Carbon Cycle” by Khan Academy is licensed under CC BY-NC-SA 3.0. Note: All Khan Academy content is available for free at khanacademy.org.

Water Cycle

Although it may seem to change, the amount of water on Earth is actually constant. However, the water’s physical state and its location change in a process called the water cycle.

“The Water Cycle” by John Evans and Howard Periman/USGS is public domain

Key Terms in the Water Cycle

- Liquid water evaporates from Earth’s surface or bodies of water and enters the atmosphere as a gas called water vapor.

- Water vapor condenses into tiny liquid water droplets which form clouds.

- The water droplets combine into larger drops and precipitation such as rain occurs.

- Sometimes, water in clouds skips the liquid precipitation phase and goes straight from water vapor to solid form. This process, called desublimation, results in snow. The opposite of desublimation is sublimation, where water changes straight from its solid state to gas. This process is difficult to visualize in the water cycle, but it is the same process that occurs with dry ice–when exposed to air, carbon dioxide from solid dry ice is released in the form of gas through sublimation.

- When precipitation hits the surface of Earth, it becomes surface runoff. The water flows over the land and reenters bodies of water such as lakes, rivers, and oceans. where it will eventually evaporate again, thus continuing the water cycle.

- Some water will infiltrate the ground, becoming groundwater that can seep into aquifers.

- Precipitation can also evaporate from the surface of the land. Or, plants can absorb water through their roots. The water moves through the plant and is released through the plant’s leaves where it can evaporate back into the atmosphere. This process is called evapotranspiration.

“Evapotranspiration” by Salinity Management Org. is public domain

For more explanation, watch the following video from Khan Academy:

A YouTube element has been excluded from this version of the text. You can view it online here: https://pressbooks.uiowa.edu/methodsii/?p=615

Video credit: “The Water Cycle” by Khan Academy is licensed under CC BY-NC-SA 3.0. Note: All Khan Academy content is available for free at khanacademy.org.

Wind

Wind is caused when Earth’s surface is heated unevenly by the Sun. Different types of surfaces on Earth, such as land or water, absorb heat differently. Additionally, darker-colored areas absorb more heat than lighter-colored surfaces. Finally, Earth is tilted on its axis so the Sun hits certain areas of the surface more directly than others which causes temperature differences. All of these factors contribute to the uneven heating of Earth’s surface.

Remember that warm air rises and cool air descends. When warm air rises, it leaves a low pressure area behind. In order to maintain balance, air from a cooler, high-pressure area moves in to fill the space and wind occurs.

“Wind” by NOAA is public domain

15

Before the Flood

The link below is a guide to use while watching Before the Flood (2016). This is not required for class, but can be used as an additional resource.

Click here to access and download the watching guide.

“The Garden of Earthly Delights” by Hieronymus Bosch is public domain

16

Climate Science Practice Quiz

Follow this link to take the climate science practice quiz. You will get immediate feedback on your answers.

“La Fortuna Waterfall Costa Rica” by Boris G is licensed under CC BY-NC-SA 2.0

In addition to the content presented in the first three sections, pedagogy for science teachers is an important part of this course. This section includes the following chapters:

1. Big Ideas: Key topics for pedagogy in this course

2. Course Readings and Videos: Links to course materials

3. Helpful Links: Links to additional resources for science education

17

Big Ideas

Key ideas of pedagogy in this class

The following TED Talk discusses the history of our education system, current issues in education, and ways we can reform education to be more relevant for the future. This video is highly recommended viewing.

A YouTube element has been excluded from this version of the text. You can view it online here: https://pressbooks.uiowa.edu/methodsii/?p=743

Video Credit: “Changing Education Paradigms” by Sir Ken Robinson and RSA Animate. TED Talks are licensed under CC BY-NC-ND 4.0

Misconceptions

18

Course Readings and Videos

Click on the links below to access the Science Methods course readings and videos

Five Good Reasons to Use Science Notebooks

Gilbert, J. & Kotelma, M. (2005). Five good reasons to use science notebooks. Science and Children, November/December, 28-32.

A Private Universe

A Vimeo element has been excluded from this version of the text. You can view it online here: https://pressbooks.uiowa.edu/methodsii/?p=715

Harvard-Smithsonian Center for Astrophysics. (1987). A private universe [Video documentary]. Retrieved from https://vimeo.com/113349804

Introduction to Earth/Space Science

National Research Council (2012). A framework for k-12 science education: Practices, crosscutting concepts, and core Ideas. Washington, DC: The National Academies Press. https://doi.org/10.17226/13165.

Space Science Overview

Rutherford, F. J. (1990). The physical setting. In Science for all Americans online (Chapter 4). Retrieved from http://www.project2061.org/publications/sfaa/ online/chap4.htm

Misconceptions Die Hard

Stepans, J. I., Beiswenger, R. E., & Dyche, S. (1986). Misconceptions die hard. The Science Teacher, September, 65-69.

Sweater Article

Watson, B. & Konicek, R. (1990). Teaching for conceptual change: Confronting children’s experience. Phi Delta Kappan, May, 35-40.

Environmental Education–School of the Wild

Braus, J.A. & Wood, D. (1993). Environmental education in the schools: Creating a program that works. Peace Corps Information Collection and Exchange. 4-13.

19

Helpful Links

Next Generation Science Standards (NGSS)

Science Methods 2 YouTube Channel

1

Glossary

Air Mass

A large body of air that takes on the climatic conditions of the area where it is formed.

Albedo

The amount of energy reflected by a surface. Light surfaces tend to have a high albedo because they reflect more energy. Dark surfaces tend to have a low albedo because they absorb more energy.

Aquifer

An underground area of rock that stores groundwater. Humans often pump out groundwater from aquifers or use them as a source for wells.

Asteroid

Rocky celestial bodies left over from the formation of the solar system that are smaller than planets and orbit the Sun.

Big Bang Theory

Scientific theory for how the universe was created.

Black Hole

An area in space with extremely strong gravity from which no light can escape.

Boundary

The border between two tectonic plates.

Buoyancy

the ability or tendency to float in water or air or some other fluid

Climate

The typical weather conditions in an area over a 30-year period.

Climate Change

A significant change over a 30-year period from the typical or expected weather patterns of an area. Modern climate change is human-caused.

Comet

A frozen ball of gas, rock, and dust that orbit the Sun. When a comet gets close to the Sun, it heats up and the gas and dust form a tail.

Condensation

Process by which water changes states from water vapor to liquid water.

Continental Drift

Theory that states that all of Earth's land was originally a united supercontinent that drifted apart over time. This theory was eventually replaced by the theory of plate tectonics.

Continental Plates

Less dense tectonic plates that make up the surface of land on Earth.

Convergent Boundary

Tectonic plates push into each other.

Core

The innermost layers of Earth; made of a liquid outer core and a solid inner core.

Crater

Depression formed by an impact.

Crust

The outermost layer of Earth.

Desublimation

Process by which water vapor (gas) converts straight to solid form, resulting in snow.

Divergent Boundary

Tectonic plates pull apart from each other.

Ecosystem

An interconnected community of all the living organisms and the physical landscape of an area.

Equinox

The day when there is an equal amount of day and night (12 hours each). Occurs when the Sun shines directly on the Equator.

Erosion

Process by which broken down rocks are carried to a new location.

Evaporation

Process by which water changes states from liquid to gaseous water vapor.

Evapotranspiration

Process by which water evaporates from the surface of the land or from plant's leaves.

Fault

Break or crack in the plates on Earth's crust.

Fossil Fuels

Finite sources of energy derived from ancient remains of decomposing organisms. The main fossil fuels are coal, oil, and natural gas.

Galaxy

A collection of billions of stars, gas, and dust held together by gravity in space.

Geocentrism

The theory that Earth is at the center of our solar system, and the Sun and other planets revolve around it.

Geode

a rock containing a cavity lined with crystals or other mineral matter

Greenhouse Gas

An asymmetrical gas in Earth's atmosphere that traps heat. The main greenhouse gases are carbon dioxide, nitrous oxide, methane, and water vapor.

Heliocentrism

The theory that the Sun is at the center of our solar system.

High Pressure System

Air pressure on Earth is higher than normal, so air descends. A high pressure system is associated with good weather--sunny and clear skies.

Hot Spot

An extremely hot area located in the center of a tectonic plate where magma can rise to the surface. Some volcanoes are located over hot spots, rather than at tectonic plate boundaries.

Infiltration

The process by which surface water soaks into the ground.

Island Arc

A chain of islands in the ocean in an arc shape. Formed by two convergent oceanic plates and volcanic eruptions.

Jet Stream

A large current of wind which carries warm and cold air masses to different areas of Earth.

Latitude

A location's distance from the Equator.

Law of Original Horizontality

Due to the pull of gravity, new rock is initially formed in flat, horizontal layers.

Law of Superposition

Deeper layers of rocks are older than layers closer to the surface.

Lithosphere

Part of Earth made of the crust and the upper molten part of the mantle.

Low Pressure System

Air pressure on Earth is lower than normal, so air rises. A low pressure system is associated with bad weather--clouds, rain, and wind.

Magma

Molten rock beneath Earth's surface.

Mantle

The middle layer of Earth between the crust and the core.

Meteor

The streak of light that is caused when a meteoroid enters Earth’s atmosphere and burns up due to friction. Also known as a shooting star.

Meteorite

A meteoroid that survives its trip through the atmosphere and lands somewhere on Earth. The impact of a meteorite can cause a crater on the surface of a planet.

Meteoroid

A small rock in space that orbits around the Sun. Most meteoroids have broken off of larger objects such as asteroids or comets. They can be as small as a grain of sand or as large as a pickup truck.

Mid-Ocean Ridge

An underwater chain of mountains formed at a divergent plate boundary.

Nebula

A cloud of gas and dust in space.

Nuclear Fusion

The process by which stars get their energy. Atoms fuse together creating a nuclear reaction which releases energy in the form of heat and light in the star.

Oceanic Plates

Denser tectonic plates that make up the ocean floor on Earth.

Pangaea

A supercontinent made of all of Earth's landmass that existed 200-250 million years ago.

Plane of the Ecliptic

The disk-shaped plane in which everything in our solar system orbits around the Sun.

Plate Tectonics

Theory that Earth's crust is divided into many pieces, called tectonic plates, which move over time due to convection currents in the mantle.

Positive Feedback Loop

A process where one change triggers the next in a continuous cycle that encourages the initial change.

ppm

Parts per million; a unit of measurement for carbon dioxide and other gases in the atmosphere.

Precipitation

Heavier water droplets condense and fall from clouds to Earth's surface in the form of rain, snow, or hail.

Rain Shadow

A desert area that is created when a mountain blocks precipitation from passing to one side.

Red Giant

Phase in a star's life cycle where it greatly increases in size as it burns fuel through nuclear fusion.

Ring of Fire

An area in the Pacific Ocean bounded by several tectonic plates. Due to tectonic activity along these plates, this area has a high number of earthquakes and volcanic eruptions.

Snowball Earth

A period of extreme glaciation where a positive feedback loop led to Earth being covered almost entirely by ice.

Solar System

Our Sun and all of the planets and other bodies in space (comets, asteroids, meteoroids) that orbit around the Sun in the plane of the ecliptic.

Subduction

When two tectonic plates converge, the denser plate is pushed under the other.

Subduction Zone

The boundary between two convergent tectonic plates where one plate subducts under the other.

Sublimation

Process by which water changes straight from its solid state to gas. This is the same process that occurs with dry ice--when exposed to air, carbon dioxide is released in the form of gas through sublimation.

Summer Solstice

The day with the most sunlight. In the Northern Hemisphere this occurs when the Sun shines directly on the Tropic of Cancer.

Supernova

The giant explosion of a supermassive star at the end of its life cycle.

Thermal Expansion

An increase in the volume of matter when its temperature increases.

As global temperature increases, ocean water heats and expands which contributes to sea level rise.

Topography

The physical features of an area of land.

Transform Boundary

Tectonic plates sideswipe each other.

Trench

A long depression formed on the ocean floor from the convergence of two oceanic plates. Trenches are some of the deepest place on Earth's surface.

Volcano

A vent that allows magma, rock fragments, ash, and gases to escape to the surface of a planet or moon.

Water Cycle

Process of how water in different states continuously moves on, above, and below Earth's surface.

Weather

The short term atmospheric conditions in an area.

Weathering

The breakdown of rocks on Earth's surface

Winter Solstice

The day with the least of sunlight. In the Northern Hemisphere this occurs when the Sun shines directly on the Tropic of Capricorn.