Transcript 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: Hoe Do Movements of the Crust Change Earth?
Lesson 1: VOCABULARY
 Landform: a natural shape of 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, flattopped 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:
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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
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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
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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
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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.