Weathering, Erosion and Deposition.(3rd/4th grade teach)
Weathering, Erosion and
By Moira Whitehouse PhD
The Earth’s surface is constantly changing.
Mount St Helens before and after it erupted in 1980.
New land is constantly being formed.
Forces deep in
the Earth push
up chains of
Land is being constantly worn down by wind,
water and ice. original
• The breaking down of rock into
smaller and smaller pieces.
Some things in nature that cause
Water in cracks in the rock freezing and
Plant roots growing into rocks
Water running over rocks, causing the
rocks to hit one another and break into
Wind carrying sand that wears away rock
Carbon dioxide dissolved in water forming
an acid that eats holes in the rock
Water in cracks in the rock freezes.
As it freezes it expands causing the
rocks to break.
Expanding water as itwedgingslowly breaks up this
Frost Action or ice freezes slowly breaks up this
sedimentary rock into unusual shapes.
rock into unusual shapes.
Weathering by glaciers
A glacier is a large,
river of ice that
moves very slowly
Glaciers are formed
over many years as
large amounts of snow
fall and accumulate.
The snow compacts
and changes to ice.
Stuck in the bottom of the glacier are stones
of various sizes that wear away the rock
under the glacier as it moves downhill.
Striations or scratches made in the rock
under a glacier by the stones stuck in it as
the glacier moved downhill.
Carbon dioxide that dissolves in water
• CO2 dissolves in rain water and creates
• Carbonic acid easily weathers limestone
making holes in the rock
The process by which
water, ice, wind or
gravity moves pieces
of rock and soil.
When rock is
into smaller and
smaller pieces), these
pieces are often
carried away by water,
wind or ice.
Rivers, streams, and runoff carry weathered
rock or soil to another place.
rivers carry big
Slower moving water carries smaller rocks
and soil downstream.
Moving water can also cause soil erosion—
carrying the soil away to a different location.
Sometimes a side of the hill is washed away
by running water. The soil and rocks move
down the hill in a landslide.
This simple animation provides
you with a visualization of how
the Colorado River has
"downcut" into the rock layers of
the Grand Canyon.
Canyons demonstrate both
weathering—the breaking down
of rock into smaller pices and
Canyons are large erosion—these pieces of rock
valleys created by a being moved to a new location.
river or stream.
Strong winds can move small rocks and soil from
one location to another.
Glaciers moving over
rocks breaks them down
into smaller pieces
(weathering) and carries
them away (erosion).
When the water slows down or
When the wind dies down or stops
When the glacier melts
the rocks that the water, wind or
glacier were carrying are dropped or
deposited in a new location.
Where a river meets the ocean is called the
mouth of the river. Soil carried by a river is
deposited at the mouth and new land is formed.
This new soil-rich land is known as a delta.
Sand dunes are large deposits of sand
dropped when the wind stopped blowing. The
location of the sand dunes shifts frequently.
When glaciers melt, they drop or deposit the rocks
they were carrying.
A moraine is the
rocks and soil left
behind by a melting
pick up rocks and
dirt that travel along
with the glacier until
it eventually melts
and is left behind as
Although we talk about weathering, erosion and
deposition as three separate processes, they often
occur together. Over time, rocks are generally broken
into smaller pieces (weathering) carried downhill
(erosion) and deposited in a new location (deposition).
Do you remember the agents of weathering
that we discussed?
moving water in water in cracks in rocks
streams and rivers freezing and expanding
glaciers plant roots wind
Do you remember the agents of erosion that
moving water in glaciers
streams and rivers