Changes to Earth

1
Changes to Earths SurfaceChapter 9

• Lesson 1 What Are Some of Earths Landforms?
• Lesson 2 What Causes Changes to Earths
  Landforms?
• Lesson 3 Hoe Do Movements of the Crust Change
  Earth?

2
Lesson 1 VOCABULARY

• Landform a natural shape of feature of Earths
  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.

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Lesson 1 What are some of Earths landforms?

• The land has many shapes.
• A landform is a natural shape or feature.
• There may be several landforms in a certain area
  (topography).

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Lesson 1 What are some of Earths 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.

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Lesson 1 What are some of Earths 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.

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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.

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Lesson 2 What causes changes to Earths
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.

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Lesson 2 What causes changes to Earths
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.

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Lesson 2 What causes changes to Earths
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.

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Lesson 2 What causes changes to Earths
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.

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Lesson 2 What causes changes to Earths
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.

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Lesson 2 What causes changes to Earths
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).

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Lesson 2 What causes changes to Earths
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.

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Lesson 3 VOCABULARY

• Earthquake a shaking of the ground caused by a
  sudden release of energy in the Earths crust.
• Epicenter the point on the Earths surface
  directly above an earthquake.
• Plate A block of Earths crust and mantle. (They
  fit together like puzzle pieces)
• Fault a break in the Earths crust.
• Magma melted or molten rock that forms under the
  Earths surface.
• Lava is magma that reaches Earths surface.
• Volcano a mountain of lava, ash, or other
  materials from eruptions.

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Lesson 3 How do movements of the crust change
Earth?

• Earths structure
• Earth has 4 main layers and each layer is quite
  different.
• Inner core
• Outer core
• Mantle
• Crust

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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.

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Lesson 3 How do movements of the crust change
Earth?

• Earths 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 Earths
  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 Earths
  surface looks.

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Lesson 3 How do movements of the crust change
Earth?

• Volcanoes
• Melted rock beneath Earths 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 Earths
  surface.
• The magma that flows onto Earths surface turn
  into lava.

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Lesson 3 How do movements of the crust change
Earth?

• Earthquakes
• When Earths 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 Earths surface directly above the
  focus is called the epicenter.
• Earthquakes often occur along a fault,
• or a break in Earths crust.

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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 Earths tallest
• landforms.