Chapter 2 Lesson 3Chapter 2 Lesson 3How Do Movements Of How Do Movements Of

The Earth’s Crust The Earth’s Crust Change Landforms?Change Landforms?

S5E1A: Students will identify features caused by S5E1A: Students will identify features caused by destructive/constructive processes destructive/constructive processes

Vocabulary PreviewVocabulary Preview

PlatePlate: a section of Earth’s crust and : a section of Earth’s crust and mantle that fits together with other mantle that fits together with other sections like puzzle piecessections like puzzle pieces

EarthquakeEarthquake: a shaking of the Earth’s : a shaking of the Earth’s surface, caused by movement of rock surface, caused by movement of rock in the crustin the crust

EpicenterEpicenter: the point on Earth’s : the point on Earth’s surface directly above the focus of an surface directly above the focus of an earthquakeearthquake

FaultFault: a crack in the Earth’s surface: a crack in the Earth’s surface

Vocabulary PreviewVocabulary Preview

MagmaMagma: melted rock that is beneath : melted rock that is beneath Earth’s surfaceEarth’s surface

LavaLava: molten rock that flows from a : molten rock that flows from a volcano onto Earth’s surfacevolcano onto Earth’s surface

VolcanoVolcano: a mountain that forms as : a mountain that forms as molten rock flows through a crack molten rock flows through a crack onto Earth’s surfaceonto Earth’s surface

Earth’s StructureEarth’s Structure

Imagine you’re a miner digging for Imagine you’re a miner digging for gold or gems. You dig deep into Earth, gold or gems. You dig deep into Earth, maybe 1 or 2 miles down. But even at maybe 1 or 2 miles down. But even at this depth, you’ve barely scratched this depth, you’ve barely scratched Earth’s surface.Earth’s surface.

You’d need to dig down about 4,000 You’d need to dig down about 4,000 miles to reach the center of the Earth. miles to reach the center of the Earth. What do you think you’d find at the What do you think you’d find at the center?center?

Earth’s StructureEarth’s Structure You would think maybe you would find rock, but You would think maybe you would find rock, but

you wouldn’t. Earth has 4 layers-crust, mantle, you wouldn’t. Earth has 4 layers-crust, mantle, outer core, and the inner core. outer core, and the inner core.

If you could dig a hole to the center of the Earth, If you could dig a hole to the center of the Earth, you’d find that the layers are different from one you’d find that the layers are different from one another. another.

The thin crust is solid rock. The mantle also has a The thin crust is solid rock. The mantle also has a thin crust. thin crust.

But some rock within the mantle is soft, like But some rock within the mantle is soft, like melted candy. The deeper you’d go, the hotter melted candy. The deeper you’d go, the hotter things would get. things would get.

The outer core is liquid, but it’s iron, not rock. The outer core is liquid, but it’s iron, not rock. The inner core is also metal, but its solid due to in

tense pressure.

Crust 5-70 km (3-43 mi The crust is the surface layer of Earth.Mantle 2885 km (1790 mi)

The mantle has two parts: the upper mantle and the lower mantle. Most of the mantle is solid rock, but some mantle rock is soft.

Outer Core 2270 km (1410 mi) The hot outer core is liquid iron.Inner Core 1210 km (750 mi)

Inner core is iron and nickel. Even though the core is very hot, great pressure at the center of Earth keeps the inner core solid.

Layers of the Earth

Earth’s StructureEarth’s Structure Earth’s crust and uppermost mantle are Earth’s crust and uppermost mantle are

divided into sections, called divided into sections, called platesplates. . Plates are blocks of crust and upper are blocks of crust and upper

mantle rock that fits together like puzzle mantle rock that fits together like puzzle pieces. pieces.

Look at the map on the next slide. There Look at the map on the next slide. There are 10 major plates. are 10 major plates.

Most of North America, Greenland, and Most of North America, Greenland, and part of the Atlantic Ocean are on the North part of the Atlantic Ocean are on the North American Plate. American Plate.

Part of California and most of the Pacific Part of California and most of the Pacific Ocean are on the Pacific Plate. Ocean are on the Pacific Plate.

Earth’s Structure

Plates “float” on the softer rock of the Plates “float” on the softer rock of the mantle. As the rock flows, plates move. mantle. As the rock flows, plates move.

Because plates fit together so closely, the Because plates fit together so closely, the movement of one plate affect the other movement of one plate affect the other plates. plates.

At different places, plates move toward At different places, plates move toward each other, away from each other, or each other, away from each other, or alongside each other. alongside each other. These plate movements cause many changes in Earth’s surface.

Earth’s Structure

EarthquakesEarthquakes Suppose you press your Suppose you press your

palms together as hard as palms together as hard as you can. you can.

If one hand slips, energy is If one hand slips, energy is released suddenly and your released suddenly and your hands move past each other. hands move past each other.

When two of Earth’s plates When two of Earth’s plates move suddenly past each move suddenly past each other, energy is also released other, energy is also released and the ground shakes. and the ground shakes.

An An earthquakeearthquake is movement is movement of the ground caused by a of the ground caused by a sudden release of energy in sudden release of energy in the Earth’s crust. the Earth’s crust.

EarthquakesEarthquakes

The place within the crust where energy The place within the crust where energy is released during an earthquake is is released during an earthquake is called the focus. called the focus.

The release of energy may hardly be The release of energy may hardly be noticed, or it may cause a lot of noticed, or it may cause a lot of damage.damage.

The greatest damage is likely to occur The greatest damage is likely to occur directly above the focus. directly above the focus.

The point on Earth’s surface directly The point on Earth’s surface directly above the focus is called the epicenter. above the focus is called the epicenter.

An earthquake occurs when Earth’s crust moves and releases energy. The energy of an earthquake spreads out like ripples on a pond. Places farther from the epicenter are likely to experience less damage than places near the epicenter.

Earthquakes Earthquakes are caused by three different Earthquakes are caused by three different

types of plate movement. Plates pushing types of plate movement. Plates pushing together, plates sliding past each other, together, plates sliding past each other, and plates pulling apart all produce and plates pulling apart all produce earthquakes. earthquakes.

Most earthquakes occur along a fault, or Most earthquakes occur along a fault, or break in the Earth’s crust. Some faults break in the Earth’s crust. Some faults occur in the middle of plates, but most are occur in the middle of plates, but most are found near the edge of plates. Faults found near the edge of plates. Faults develop as plate movements bend and develop as plate movements bend and crack the crust. crack the crust.

EarthquakesEarthquakes

Earthquakes caused by plates or pieces of Earthquakes caused by plates or pieces of crust pushing together or sliding past each crust pushing together or sliding past each other are usually very strong. other are usually very strong.

Earthquakes caused by plates or pieces of Earthquakes caused by plates or pieces of crust pulling apart are usually weak. crust pulling apart are usually weak.

Scientists classify earthquakes by Scientists classify earthquakes by estimating their magnitude, or amount of estimating their magnitude, or amount of energy being released. This is reported energy being released. This is reported using a scale of magnitude. using a scale of magnitude.

Earthquakes This scale is called the Richter Scale. An earthquake measuring 2.0 on the scale

is too small to be felt. There are millions of earthquakes like this

every year. An earthquake measuring 6.0 or higher on An earthquake measuring 6.0 or higher on

the Richter Scale can cause a great deal of the Richter Scale can cause a great deal of damage. damage.

Each increase of 1 on the Richter Scale is Each increase of 1 on the Richter Scale is an increase in strength of about 32 times. an increase in strength of about 32 times.

About 20 earthquakes of magnitude 6.0 or About 20 earthquakes of magnitude 6.0 or greater occur each year. greater occur each year.

An earthquake in Seattle in 2001 measured 6.8 on the Richter scale and caused a lot of damage.

Major Earthquakes Read the information in the table. Then, on a world map, mark the areas where these major earthquakes occurred. Using the information in the text below, estimate how many times stronger the 1964 Alaska earthquake was than the 1976 China earthquake.

The pattern of the rocks after an earthquake clearly show the San Andreas Fault. The map shows the location of this fault

VolcanoesVolcanoes You know that there are You know that there are

places in Earth’s mantle places in Earth’s mantle where solid rock melts.where solid rock melts.

Melted, or molten, rock Melted, or molten, rock beneath Earth’s surface beneath Earth’s surface is known as is known as magmamagma. .

Magma forms in places Magma forms in places where plates push where plates push against each other or against each other or pull away from each pull away from each other. other.

Magma is less dense Magma is less dense than solid rock, so it’s than solid rock, so it’s pushed upward through pushed upward through the mantle and crust. the mantle and crust.

VolcanoesVolcanoes As magma travels upward, As magma travels upward,

it sometimes reaches an it sometimes reaches an opening, or vent, in the opening, or vent, in the crust. crust.

Magma that has flowed out Magma that has flowed out of a vent is called lava. of a vent is called lava.

LavaLava is molten rock that is molten rock that reaches Earth’s surface. reaches Earth’s surface.

As more and more lava As more and more lava flows from a vent, a flows from a vent, a volcano begins to form. volcano begins to form.

A A volcanovolcano is a mountain is a mountain made of lava, ash, or other made of lava, ash, or other materials from eruptions. materials from eruptions.

VolcanoesVolcanoes

Lava may ooze slowly out of a vent Lava may ooze slowly out of a vent or it may explode from a vent with or it may explode from a vent with tremendous force. tremendous force.

The 1883 eruption of Krakatoa in The 1883 eruption of Krakatoa in Indonesia blew lava 17 miles into the Indonesia blew lava 17 miles into the air!air!

Krakatoa before 1883 Krakatoa before 1883

Krakatoa after 1883

VolcanoesVolcanoes Some volcanoes form Some volcanoes form

above an especially hot above an especially hot column of magma. column of magma.

This column is called a hot This column is called a hot spot. A hot spot can melt a spot. A hot spot can melt a hole through the crust as hole through the crust as the magma rises to the the magma rises to the surface. surface.

As a plate moves slowly As a plate moves slowly over a hot spot, volcanoes over a hot spot, volcanoes form in new locations. form in new locations. Eventually, a hot spot can Eventually, a hot spot can produce a chain of produce a chain of volcanoes. volcanoes.

This is how the Hawaiian This is how the Hawaiian Islands were formed. Islands were formed.

Volcanoes

Composite, Shielded, Cinder Cone Volcanoes

How Mountains FormHow Mountains Form Mountains are the Mountains are the

tallest landforms on tallest landforms on Earth. Earth.

They form where the They form where the crust is crumpled and crust is crumpled and pushed upward by the pushed upward by the movements of plates. movements of plates.

Many mountains form Many mountains form where plates come where plates come together. together.

The edge of the denser The edge of the denser plate is forced into the plate is forced into the mantle, while the mantle, while the dense plate is pushed dense plate is pushed up.up.

How Mountains FormHow Mountains Form

The Appalachian Mountains are The Appalachian Mountains are mostly the result of normal faults mostly the result of normal faults folding and thrusting upwards. folding and thrusting upwards.

The Valley and Ridge region, and the The Valley and Ridge region, and the Blue Mountains, on the other hand, Blue Mountains, on the other hand, were built up by a series of reverse were built up by a series of reverse faults that force large sheets of rock faults that force large sheets of rock to pile up. to pile up.

The diagrams show two different ways The diagrams show two different ways that faults can move. that faults can move.

How Mountains FormHow Mountains Form Mountains may also Mountains may also

form in the middle of a form in the middle of a plate. plate.

Suppose you hold a Suppose you hold a cracker and push down cracker and push down on the opposite edges. on the opposite edges.

The cracker would soon The cracker would soon break, with jagged, break, with jagged, broken edges in the broken edges in the center moving up. center moving up.

This is how the Grand This is how the Grand Teton Mountains in Teton Mountains in Wyoming, formed. Wyoming, formed.

How Mountains FormHow Mountains Form

Millions of years ago, surrounding Millions of years ago, surrounding plates put tremendous pressure on plates put tremendous pressure on the edges of the N. American plate. the edges of the N. American plate.

The pressure snapped a block of rock The pressure snapped a block of rock in the middle of the plate. in the middle of the plate.

The rock rose up from the land The rock rose up from the land around it, forming mountains. around it, forming mountains.

Cloudland Canyon State Park in northern Georgia was produced by the movement of faults.

The layers of rock in this mountain in Montana are the result of reverse faults.

In a reverse fault, the rock layers above the fault move up.

In a normal fault, the rock layers above the fault move down

How Mountains FormHow Mountains Form

Plates that move apart leave gaps Plates that move apart leave gaps between them. between them.

When this happens, mantle rock When this happens, mantle rock moves in to fill the gaps. moves in to fill the gaps.

Magma builds up along plate Magma builds up along plate boundaries, forming a ridge. boundaries, forming a ridge.