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Created By: Miss. Hoover
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Some of the changes happen so slowly that you would
never see them.
For instance, it took about 6 million years for the
Colorado River to carve the Grand Canyon.
 Earth’s
surface is exposed to water,
wind, ice, and growing plants. Each
one of these can break down rocks
into smaller pieces. This breaking
down of rocks is called weathering.
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Some of the minerals in rocks dissolve in water.
When this happens under ground, huge caverns can
form.
Moving water that carries rough pieces of sand can
also chip away rocks.
 Wind
that contains sand wears away rock
like sandpaper wears away wood.
 If you imagine workers sandblasting a
building, that is how wind can weather
rocks.
Liquid water collects in cracks in a rock.
When the water freezes, it expands.
 The expanding ice pushes apart the rock and
breaks it.
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When you look at a side of a cliff, you might
see a plant sprouting from a crack in the rock.
This process loosens and breaks off bits of the
rock.
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Erosion carries weathered materials away from a
place. Deposition drops the materials in a new place.
Erosion and deposition destroy old landforms and
create new ones. Moving water, wind, and moving
ice cause erosion and deposition.
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Rain, streams, and rivers cause erosion. When the
water moves across the land it will carry away soil,
sand, and small rocks.
When the water slows down, the materials all out and
are deposited.
 Wind
can move and deposit particles
of rock, soil, and sand.
 Wind makes the most changes when
it blows open areas such as deserts,
plowed fields, and beaches.
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Glacier is a large body of moving ice. Glaciers that
form in mountain valleys move downward very slowly.
As they move, they scrape away pebbles, rocks, and
huge boulders.
If a glacier melts and shrinks, the materials are
deposited. At this front end and its sides, the glacier
leaves behind a ridge of rocks called a moraine.
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Over millions of years, forces in Earth’s crust pushed up these
mountains in two different ways.
Folded mountains are produced when land is squeezed
together. There is a push on the land and it forces it upwards.
Fault-block mountains are produced when blocks of rock
slide upward or downward along a fault. A fault is a crack in
Earth’s crust. Land moves along in one of three ways.
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Normal fault: a block of land drops downwards. This process can form valleys
with steep hills.
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Reverse fault: a block of land is pushed upward. This is how California’s Sierra
Nevada Mountains were formed.
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Strike-slip fault: blocks of rock move sideways past each other. The San Andreas
Fault in California is a this kind of fault.
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The Earth’s crust is broken into sections and
they are called plates. The plates are always
moving, although they move very slowly.
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Rapid changes occur quickly on the Earth’s
surface. These are volcanoes, earthquakes,
tsunamis, landslides, and floods.
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Melted rock below Earth’s surface is called Magma. When the
magma heats and expands, it pushes in all directions. It moves
to the Earth’s crust. An eruption will happen and throw hot
boulders, ashes, gases, and cinders in into the air.
When the magma and gases build up and are trapped inside
the mountain for a while, the pressure is enormous. It becomes
so great, there is an explosion.
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An Earthquake happens when huge slabs of rock
move against each other deep below Earth’s surface.
The slabs will touch a fault.
The slabs stick together until the forces are pushing and
the force is so great. Then the slabs will move a short
distance. This jolt produces waves in the crust like
ripples in a pond. The waves can be felt as an
earthquake.
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A tsunamis is a giant ocean wave caused by an
undersea earthquake. When the earthquake occurs on
the ocean floor, it releases a lot of energy. The energy
travels though the water and produces a small wave on
the surface.
Finally, the wave will move outward in all directions.
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The force of gravity can cause rapid changes in the
land.
The force of gravity pulling on rocks, soil, and mud
downward creates a landslide.
Landslides will destroy structures such as hills and
cliffs. But the new land is built up at the bottom of the
landslide.
Floods will sweep land away from one place
and deposit it in another place.
 River floods are usually caused by long,
steady, heavy rains or a large amount of
melting snow.
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