Unit C - Earth Science - Grade 3

By Warren Spencer,2014-06-26 20:20
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Unit C - Earth Science - Grade 3

    Unit C - Earth Science - Grade 3

Chapter 1

    Changes in the Earth’s Surface

Lesson 1

    How Do Volcanoes and Earthquakes Change the Earth?

    - How do volcanoes form?

    - How do volcanoes change the earth? - How do earthquakes change the earth? - How do scientists study volcanoes and earthquakes?

    - How can you be safe during earthquakes?

Lesson 2

    What Landforms Are on the Earth’s Surface?

    - Where are some landforms?

    - What are some kinds of landforms?

Lesson 3

    How Do Water and Wind Change the Earth’s Surface?

    - How does weathering change rocks? - How does erosion change the earth?

Lesson 4

    How Can Living Things Affect the Earth’s Surface?

    - How do plants and animals change the earth? - How do people change the earth?


Lesson 1 pg. C8-9

    How Do Volcanoes and Earthquakes Change the Earth? How Volcanoes Form

     A volcano (vol ka no) is a special type of mountain (mown ten) with an opening at the top. It took thousands of years for the volcano to form.

     It begins deep inside the earth. The inside of the earth is very hot. It is so hot that some rocks melt and become a very thick liquid called magma (mag ma). Magma gathers far underground for hundreds and thousands of years.

     Powerful forces push the magma up to the earth’s surface. The magma erupts (e rupts) from the deep cracks in the ground. Erupt means to burst out. When magma erupts, we then call it lava (la va). Like

    magma, lava is melted rock.

    Q. Melted rock that is deep inside the earth is called ______.

    A. _____________________________________________________


Lesson 1 pg. C10

    How Volcanoes Change the Earth’s Surface

     Over time, the hot lava that comes out of a volcano cools. It becomes solid rock. As more and more lava builds up on the earth’s surface, a volcanic mountain forms. Each time a volcano erupts, more lava spreads. The volcano gets taller. Volcanoes change the earth’s surface when a volcanic mountain forms.

     Sometimes, a volcano forms under the ocean. If it gets tall enough, it will reach the surface and becomes an island (i lend). Hawaii (huh why ee) and Japan are groups of islands that formed from volcanoes.

    Q. When lava builds up after many eruptions, it forms a _______.

    A. ______________________________________________________


Lesson 1 pg. C11

    How Earthquakes Change the Earth’s Surface

     Layers of huge blocks of rock lie far below the ground. In some places deep in the earth, the blocks push against each other. The blocks usually do not move. After many years, the pushing moves one or both of the blocks.

     The surface of the earth has many large cracks. When the blocks of rock move, new cracks can form. When some of these blocks move, an earthquake (erth kwake) happens. The land above the cracks may move up, down, or sideways. An earthquake is a shaking or sliding of parts of the earth’s surface.

     Earthquakes can shake the ground a little or a lot. Like volcanoes, earthquakes change the earth’s surface.

    Q. When the rocks inside the earth move and shake, there is an ______.

    A. ________________________________________________________


Lesson 1 pg. C12

    How Scientists Study Volcanoes and Earthquakes

     Most volcanoes and earthquakes happen in the same parts of the world. Earthquakes often happen during or just before a volcano erupts.

     Scientists (sy en tists) try to predict earthquakes. There are instruments (in strew ments) that can show the tiny movements of the earth. Is an earthquake about to happen? These movements also happen before volcanoes erupt. Satellites (sat el ites) in space can also show warning signs that an earthquake or volcanic eruption might happen.

     A scientist who studies volcanoes is called a volcanologist (vol can ol o gist). They will study samples of lava to find out more about the inside of the earth.

Q. Scientists try to predict earthquakes. This means:

     a. they compare them to volcanoes

     b. they talk about them on TV

     c. they try to tell when they are going to happen


Lesson 1 pg. C13

    Safety During Earthquakes

     Earthquakes can be very dangerous. We don’t usually have any warning. You can help protect yourself if you know what to do.

     You should know how to Duck, Cover, and Hold. Go under a strong table or desk. Hold onto it. If it moves along the floor - move with it. Stay there until the ground stops shaking.

     Stay away from windows, trees, signs, electric wires, pictures on walls. Don’t go near furniture that could fall over. In school, follow your

    teacher’s instructions.

Q. Why shouldn’t you stand near a tall bookcase in an earthquake?

    A. ________________________________________________________


Lesson 2 pg. C14-15

    What Landforms Are on the Earth’s Surface?

    Landforms in North America

     The surface of the earth has many different shapes. Each kind of shape is a landform (land form). Three important landforms are

    mountains (mown tens), plains (planes), and plateaus (pla toes).

     Volcanoes are formed in thousands of years. Other mountains are formed more slowly by forces deep inside the earth. These mountains take millions of years to form. The pushing of huge blocks of rock that cause earthquakes are the forces that make these mountains. The mountains, like the Rocky Mountains, are still growing.

     In the center of the United States are the Great Plains. A plain is a large, flat area of land. A plateau is a large, flat area that is high. Our country has two main areas of plateaus.

Q. Do you think Rockford’s landform is a plain, mountain, or plateau?

    A. ________________________________________________________

     Plateau Plains



Lesson 2 pg. C16-17

    Kinds of Landforms

     You have already read about these landforms, mountains, plains, and plateaus. There are many more kinds of landforms. All landforms are shaped by some kind of force. Some forces come from inside the earth. Other forces are moving water and wind. They can work to shape a landform.

     A glacier (gla sher) is a mountain of moving ice. Glaciers form in the very cold parts of the world. They move very slowly.

     A valley is a low area between mountains or hills.

     A bay is a part of an ocean or lake. The shore of a bay goes in toward the land.

     A cliff is a very steep wall of rock or soil. Water or glaciers pushed rock or soil from the sides of hills or mountains to form them. It took thousands of years to change.

     The ocean (o shun) is all the salt water that covers most of the earth’s surface.

     A river is a stream of water. It usually flows to a lake or the ocean.

     A lake is a large body of water almost surrounded by water. It is bigger than a pond.

     A hill is a high place on the earth’s surface. They are smaller than mountains. Hills have rounded tops. Mountain tops are usually pointed.

     A coast is a place where land meets the ocean. Some coasts are sandy beaches, some are rocky cliffs. Wind and water always change them.

    Q. Name any of these landforms that we have in Rockford.

    A. ________________________________________________________


Lesson 3 pg. C20-21

    How Do Water and Wind Change the Earth’s Surface?

    How Weathering Breaks Rocks

     Landforms change all the time. All surfaces on the earth can change. Even something as hard as rock can change.

     Weathering (weth er ing) is usually a slow change. Weathering is when rocks break down and change. Weathering can be caused by several things.

     Water causes weathering in a few ways. Water can get into cracks in rocks. When it freezes it grows larger and pushes on the cracks. Cracks get larger when this happens year after year. After time, the rocks may break apart. Pieces can fall off.

     Water can also break up parts of rock. These bits of rock wash away. This could form caves.

     Plants can also break down rocks. Plant roots grow into cracks. As the roots get bigger, the rocks can break. A tree root could break a very large rock.

     A good example of weathering that you can see is a pothole in the street. Water gets into a crack, freezes, melts, freezes again. After time the rock in the street gets weak. The cars that drive over it break it up.

Q. Weathering is when ______ break down and change.

    A. ________________________________________________________


Lesson 3 pg. C22-23

    How Erosion Changes the Earth’s Surface

     Each year, wind, water, and gravity move weathered rocks and soils. The moving of the rock and soil is erosion (e ro shun).

     Erosion changes the earth’s surface everywhere. These changes usually happen slowly. Sometimes erosion can be fast.

     The Grand Canyon was formed by the moving waters of the Colorado River. It took thousands of years for the water to erode bits of rock and cut the canyon deeper and deeper.

     A glacier is a mountain of moving ice that forms over many years. Glaciers move slowly. They carry rocks and leave them as they move and melt. They also push soil away.

     Wind erosion mostly happens in dry, sandy places. Strong winds can carry small bits of sand a long way. When the wind slows, the sand drops. Sand blown by wind can hit against rock. After many years, some of the rock will wear away.

     Gravity is a force that pulls objects down. It can cause erosion. It causes rocks and dirt to move down slopes. Rain helps gravity work quickly. After a big rainfall, a mud slide can happen right before your eyes.

Q. Which of these kinds of erosion can happen fast?

    A. ________________________________________________________


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