Changes to Earth’s Surface Chapter 9

Changes to Earth’s Surface

Chapter 9

Lesson 1: What Are Some of Earth’s Landforms?

Lesson 2: What Causes Changes to Earth’s Landforms?

Lesson 3: How Do Movements of the Crust Change Earth?

Lesson 1: VOCABULARY

Landform: a natural shape or feature of Earth’s surface.

Topography: is all the kinds of landforms in a certain place.

Glacier: is a large, thick sheet of ice that stay frozen all the time.

Sand dune: is a hill of sand that was formed and shaped by the wind.

Lesson 1: What are some of Earth’s landforms?

The land has many shapes.

A landform is a natural shape or feature.

There may be several landforms in a certain area (topography).

Lesson 1: What are some of Earth’s landforms?

A mountain is a high landform that often occurs in groups (ranges).

A volcano is a kind of mountain but usually occur by themselves.

Hills are landforms that are similar to mountains but much lower and have rounded slopes.

A plain is a large, flat area.

Lesson 1: What are some of Earth’s landforms? A glacier is a large, thick

sheet of ice and when they move they can change how the land looks around them.

A sand dune is a hill made of sand and cause by the wind.

A mesa is a tall, flat-topped rock formation that forms when running water erodes away the rock nearby.

Canyons are deep valleys with steep sides.

Lesson 2: VOABULARY

Delta: is an area of new land at the mouth of a river. A delta is formed from sediments carried by the river.

Sinkhole: is a large hole formed when the roof of a cave collapses.

Lesson 2: What causes changes to Earth’s landforms? Changes cause by

WIND: Wind carries sand, which hits

rock. Over time the rock wears away

and changes in shape and size.

This process is called weathering.

Wind also carries sand and creates piles of sand until they become a sand dune.

Lesson 2: What causes changes to Earth’s landforms?

Changes cause by EROSION:

The sides and bottom of a river are mixed with sand and clay (sediment).

The moving water in the river causes erosion when the water picks up and carries away sediment.

This erosion can cause the shape and depth of the river to change.

Rain can also cause erosion as it falls on a hill or mountain and runs downhill.

The rain picks up the sediment and carries it downward.

Ocean waves also cause erosion by moving sand and shells on a beach.

When waves crash again rocks, they also carry away bits of rock.

Constant wave action can carve shorelines into cliffs which is also a form of erosion.

Lesson 2: What causes changes to Earth’s landforms? Changes caused

by DEPOSITION: The process by which

sediment drops out of the water is called deposition.

Some river deposit sediments at their mouth and a delta is formed.

A delta is an area of new land at the mouth of a river.

When flooding occurs, sediment from the river will be carried onto land.

The water will eventually go down but the sediment remains. This is also deposition.

Lesson 2: What causes changes to Earth’s landforms? Changes caused by SINKHOLES: Water underground (groundwater) causes rock under

the soil to erode which causes a cave to form. Sometimes a roof of a cave collapses from the weight

of the material above it. This is how a sinkhole is formed in the earth.

Lesson 2: What causes changes to Earth’s landforms? Changes caused by

LANDSLIDES:

Gravity can also cause changes to the land.

It can make soil, mud, and rocks move quickly down a slope which is called a landslide.

These often happen quite quickly and after a heavy rain when the soil is soaked with water.

Lesson 2: What causes changes to Earth’s landforms? Changes cause by ICE: Rainwater can go into cracks

and openings in rocks. During the winter the water will

freeze and expand. This makes the cracks and

openings in the rocks bigger. After this happens several times

a rock will break into pieces. Glaciers can change the shape

of landforms when they move and scrape the landscape.

When glaciers melt, they leave large amounts of sediment behind (moraines).

Lesson 2: What causes changes to Earth’s landforms? Changes caused by PLANTS: When a tree or other plant grows, its roots may grow

in small openings of rocks and cause the rock to break.

Earthworms and other animals break these small pieces down even more.

Lesson 3: VOCABULARY Earthquake: a shaking of the ground caused by a

sudden release of energy in the Earth’s crust. Epicenter: the point on the Earth’s surface directly

above an earthquake. Plate: A block of Earth’s crust and mantle. (They fit

together like puzzle pieces) Fault: a break in the Earth’s crust. Magma: melted or molten rock that forms under the

Earth’s surface. Lava: is magma that reaches Earth’s surface. Volcano: a mountain of lava, ash, or other materials

from eruptions.

Lesson 3: How do movements of the crust change Earth? Earth’s structure: Earth has 4 main layers

and each layer is quite different.

Inner core Outer core Mantle Crust

Lesson 3: How do movements of the crust change Earth? The thin crust is solid rock. Some of the mantle is solid rock and

some is softer, like melted candy. The outer core is liquid iron. The inner core is also iron but has

become solid because of the great pressure it bears.

Lesson 3: How do movements of the crust change Earth?

Earth’s crust and mantle are broken into different pieces that fit together like a puzzle.

These pieces are called plates.

There are 10 major plates covering the Earth’s surface.

The plates float on the soft rock of the mantle.

As the mantle moves, so do the plates.

Sometimes the plates push together and sometimes they move apart.

Each kind of movement can change how the Earth’s surface looks.

Lesson 3: How do movements of the crust change Earth? Volcanoes: Melted rock beneath Earth’s

surface is called magma. Magma forms in places

where plates meet up. When magma finds a vent

(opening) between the plates it sometimes pushes through to Earth’s surface.

The magma that flows onto Earth’s surface turn into lava.

Lesson 3: How do movements of the crust change Earth? Earthquakes: When Earth’s plates push or scrape against one another

energy is released in the crust and an earthquake will occur.

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

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

Earthquakes often occur along a fault, or a break in Earth’s crust.

Lesson 3: How do movements of the crust change Earth? How Mountains Form: Some plates are moving toward each other and they

sometimes crash together. The edges of the plates may be pushed up and

continue to move toward each other and eventually the crust is pushed upward.

In this case, mountains are formed. Mountains are Earth’s tallest

landforms.