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Plates Rigid blocks of crust and upper mantle rock.

Earthquake A shaking of the ground caused by the sudden release of

energy.

mountains A landform that is much higher than the land around it.

landform Physical (natural) feature on Earth's surface.

volcano A volcano is an opening, or rupture, in Earth's surface or

crust, which allows hot, molten rock, ash, and gases to escape

from below the surface.

crater A large basin formed at the top of the volcano when it fell in

on itself after the eruption

vent A rocky opening in Earth's surface through which magma

flows onto the surface.

Magma molten rock from Earth's mantle

fault A break in the crust along which rock moves.

Weathering The process by which rocks are broken down into smaller

pieces.

Erosion The movement of weathered rocks and soil from one place to

another

Continental drift The theory of how Earth's continents move over its surface.

Seismograph An instrument that records earthquake waves.

deforestation The cutting, clearing, and removal of forest or rainforest

ecosystems.

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Earth is made up of three layers which are:

1. The crust 2.the mantle 3. the core

Earth's crust is the layer we can walk on.

The crust includes the rock of the ocean floor and large areas of land called

continents

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Below the crust is the mantle. It is the thickest layer of the planet.

Most of the mantle is solid rock. Some of this layer, though, is partly melted.

This partly melted rock flows slowly like a very thick liquid.

Deep inside Earth is the core.

The core is dense ball made mostly of two metals, iron and nickel.

Earth’s core can be divided into two layers, the inner core and the outer core.

The outer core is a pool of hot, liquid metal.

The inner core is a solid ball made mostly of iron and nickel. It is the hottest

layer of Earth.

Earth's surface is not a single piece of rock. Instead, it is made up of many

plates.

Earth’s crust and upper mantle are broken into continent-sized slabs called

plates. There are 12 major plates in all.

Plates that form the ocean floor are called oceanic plates or oceanic crust.

Plates that form the continents are called continental plates or continental crust.

Continental crust is less dense that oceanic crust.

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Earth's plates fit together like the pieces of a jigsaw puzzle.

Although these plates are enormous, they actually float on soft rock of the

mantle.

Pressure and heat within the Earth produce currents in the soft rock of the

mantle. As the mantle moves, the plates floating on it move, too.

Plates move very slowly across Earth’s surface on a thin layer of partly melted

mantle.

Most plates move only a few centimeters a year. But because plates are next to

each other, the movement of one plate affects other plates.

Plates can move a way from each other, toward each other, or slide past each

other. As plates move around, they cause great changes in Earth's landforms as

shown in the following table.

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Plate motion Changes in Earth's landforms

On land On the ocean floor

toward each other

(colliding)

Mountains rise and

volcanoes erupt

e.g. America's Andes

Mountains

Deep trenches form.

Pull apart

Valleys dotted with

volcanoes develop.

e.g. Africa's Great Rift

Ridges and volcanoes form

(This spreading forms new

sea floor at the ridges)

Scrap and slide past

each other Can form earthquakes

Can form earthquakes.

And earthquakes can cause

tsunamis.

Plates move in different

ways

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Mountain formation

Mountains are the Earth's highest landforms. They form as the crust folds,

cracks, and bends upward because of the movement of Earth's plates.

Many of the highest mountains form where continental plates collide. E.g. the

Himalayas.

At some places, continental and oceanic plates collide. Because continental rock is

less dense than seafloor rock, the continental plate moves up and over the

oceanic plate. E.g. the Cascade Mountain near the Pacific ocean.

Some mountains form where pressure from movement at the boundaries pushes a

block of rock upward. E.g. the Grand Tetons.

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Plates that pull apart leave gaps between them. Magma bubbles up between the

plates. Magma builds up along the cracks, forming long chains of mountains under

the ocean. These mountains called mid-ocean ridges. E.g. The Mid-Atlantic Ridge.

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Earthquakes

An earthquake is a shaking of the ground caused by the sudden release of energy

in Earth's crust.

The energy released as plates crush together, scrape past each other, or bend

along jagged boundaries can cause great damage.

Earthquakes also occur along faults in the crust. As Earth's crust can bend or

break in the middle of a plate as forces press in on it. These breaks can form

faults, or places where pieces of the crust move.

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An earthquake sends out energy in the form of seismic waves.

Seismic waves are like ripples that form on a pond when a stone is tossed in.

Scientists measure and record seismic waves on an instrument called a

seismograph.

Scientists also use numbers to measure earthquakes. The Mercalli

scale measures the movement and damage that an earthquake

causes. The scale uses Roman numerals from I to XII.

We are more familiar with the Richter scale. This scale uses the numbers 1 to 9

to measure the energy an earthquake releases.

A seismograph has two main parts: a pen and a paper-covered rotating drum

For further reading about seismograph visit the following site

http://slohs.slcusd.org/pages/teachers/rhamley/Plate%20Tectonics/seismogra

ph.html

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Volcanoes

A volcano is a mountain that forms when red-hot melted rock flows through a

crack onto the Earth's

surface.

Melted rock inside Earth is called magma.

Some Effects of Earthquakes

Leave cracks in Earth's

surface

Destroy building and

cities

Cause big sea waves called tsunamis

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Melted rock that reaches Earth's surface is called lava.

Ways A Volcano Can Form

1-Some volcanoes form in the ocean where plates are moving away from each

other. As the plates move a part, magma slowly rises toward the surface from

deep in the mantle.

When the magma gets to the surface, it cools and hardens to form new ocean

floor.

2- Other volcanoes form where plates are moving toward each other. When a

plate made of ocean crust collide with, or hits, one made of continental crust, the

plate made of ocean crust forced down into the mantle. There it partly melts,

forming magma.

The magma flows onto the surface through a rocky opening called a vent to form

a volcanic mountain

3- Some volcanoes form when a plate moves over a

hot spot in the mantle.

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Fountains of hot rock punch through the crust to form volcanoes.

The following figure shows the different parts of a volcano

The following figure shows some effects of volcanoes.

Some Effects of volcano

Cover the land with ash and lava

Blow off mountaintops

Send out clouds of ash, rocks, and gases

Can burn nearby areas

N.B. although volcanic eruptions

are often harmful, they can have

good effects on the land around

them. The soil around an active

volcano often has minerals that

help crops grow

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Continental Drift

Earth's surface has not looked the way it does today.

The surface is constantly changing because of continental drift.

The following diagram summarizes the theory of continental drift.

According to the theory, about 225

million years ago, all of the land on

Earth was joined together in one super

continent called Pangea.

Evidence suggests that about 200 million

years ago, Pangea broke into two big

continents. The southern one, Gondwana and

the northern continent, laurasia.

Earth's surface may look even different

in the future.

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Evidence supporting continental drift

Fit of the Continents: Noted the similarity in the coastlines of North and

South America and Europe and Africa. Today the fit is done at the continental

shelf and it is nearly a perfect match.

Fossil Similarities: Mesosaurus, reptile similar to modern alligator which lived

in shallow waters of South America and Africa.

Rock Similarities: Rocks of same age juxtaposed across ocean basins.

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Paleoclimatic Evidence: Glacial deposits at equator / Coral reefs in Antarctica

For further reading about continental drift visit the following web

site

http://geology.csupomona.edu/drjessey/class/Gsc101/Plate.html

Earth's surface also can change due to some forces such as

weathering and erosion. . (Revise Earth and Space summary

for 1st. semester p. 6-8)

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Some Ways in Which Humans Can Change the Land

Human activities can cause changes to Earth

Some human activities can cause catastrophic changes to Earth's surface as

shown in the following diagram.

Human beings can change the Earth's surface.

Humans make these changes to obtain their needs.

Deforestation is one kind of these changes.

People obtain wood, paper, food, and other resources from the plants and animals

in these forests.

deforestation

Mining resources

buildings

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Some natural resources found under the Earth's surface such as coal and oil.

To find these resources, humans need to mine them.

Mining can be done in several ways such as digging tunnels deep under the ground,

or scrape away soil and rocks.

Mining also causes changes to the land.

Buildings, roads, houses, and parks around us are built by humans and as such, are

changes to the land.

Human activities also can cause greenhouse effect. (Revise Earth and Space

summary for 1st. semester p. 9-11)

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Use the terms below to complete the sentences below Weathering Erosion Crust Mantle Core Plate Magma Volcano Earthquake Fault Continental Drift Pangea fossils

1. An …………………….. is a sudden release of energy in Earth's …………….. causing

the ground to shake.

2. A rigid block of Earth's crust and upper mantle rock is a ……………..

3. The remains or traces of past life found in Earth's crust are called…………..

4. Molten rock from Earth's mantle is ………………

5. A …………………. Is a break in Earth's crust, along which pieces of crust move.

6. …………………… is the process of breaking rock into silt, sand, and other tiny

pieces called sediment.

7. Laval is magma that reaches Earth's surface through an opening, called a

…………………….., in Earth's crust.

8. The …………………. Is the layer of rock beneath Earth's crust.

9. The theory that the continents move over Earth's surface is

……………………………….

10. …………………….. is the supercontinent that held all of Earth's land 225 million

years ago.

11. …………………… is the process of moving sediment from one place to another.

12. The …………….. is the center of Earth.

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Circle the letter of the best choice

13. Gondwana and Laurasia were formed by ……..

A. continental drift B. erosion C. deposition D. earthquake

14. Which of the following is not an ancient continent?

A. Pangea B. Laurasia C. Gondwana D. inner core

15. Scientists use a ………… to measure earthquake waves.

A. lava B. thermometer C. seismograph D. vent

16. A vibration of Earth's crust is an …..

A. earthquake B. plate C. volcano D. flood

17. Most of the magma from a volcano comes up through a rocky opening

called………………..

A. Pangea B. vent C. crater D. inner core

18. Earth's crust and upper mantle are broken into several…………….

A. epicenters B. faults C. plates D. oceans

19. A mountain that forms from lava is a ………

A. continent B. volcano C. Gondwana D. crust

20. The layer of Earth tha is the hottest is the ………

A. mantle B. outer core C. crust D. inner core

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Answer the following questions

21. What are Earth's three main layers? (illustrate your answer with a labeled

drawing)

22. How fast do Earth's plates move?

23. What are two scales that scientists use to measure earthquakes?

24. What causes and Earthquake?

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25. How do scientists measure the damage caused by an Earthquake?

26. How do many of the highest mountains form?

27. What is magma and where does it come from?

28. What is deforestation?

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A B

29. How can humans change the land?

30. What is the difference between weathering and erosion?

31. The following pictures show some changes that are made by humans.

Write the kind of change under each picture.

A

B

C

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