Transcript What is Erosion?

Residual/Transported Soils,
Erosion, and Erosion History
Parent Material
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Classified as either
residual or
transported
Residual- soils that
formed in their
present location from
the bedrock beneath
Bedrock- The solid
rock beneath the soil
Example: Sandstone
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Sandstone
soils form
from
sandstone
bedrock
producing dry
coarse soil.
(mountain
ridges)
Example: Limestone
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Limestone soils come from
limestone bedrock
producing soil good for
farming. (Lancaster)
Transported Soils
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Soils that have been moved from their original location
Glacial Till
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Rocks and soils moved by glaciers
Aeolian
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Soil moved by wind
Colluvial
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Fallen rocks and soil along cliffs and slopes
Alluvial
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Soil moved by water (flooded stream banks)
What is Erosion?
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The movement of soil
by wind or water to
some new location.
Naturally a slow process
but speeds up quickly
when it is exposed.
Billions of tons of
exposed topsoil are
lost each year to
erosion
Erosion History: Early Settlers
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The invention of the plow
greatly increased the
amount of erosion by
exposing large areas of
farmland
Early colonists would grow
one crop (monoculture) in
the same place every year
until the nutrients were
used up and then they
would move on leaving
exposed soil behind.
Erosion History: Early Settlers
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Colonists moved west to the great plains
where the soil was rich in organic matter.
Erosion History: Early 1900’s
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Farmland increased rapidly
and by the 1930’s giant
dust clouds of soil blew
across the county due to
dry exposed soil. (dust
bowl)
The government created
the Soil conservation
Service (SCS) (now the
NRCS) within the Dept. of
Agriculture to conserve the
nation’s soils.
The NRCS maps and
surveys soil to plan
methods of soil
conservation.
Erosion History: Late 1900’s
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Modern technology
has allowed the U.S.
to increase its
production allowing it
to produce more food
than needed.
In the 70’s the U.S.
started growing grains
for other countries
adding to the erosion
problem (dust storms
in CA.)
Erosion History:
Today
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Many conservation
practices are still ignored
when using large
machinery because
many practices are more
difficult to do on a large
scale.
Besides farming,
highway construction,
building construction,
overgrazing and some
logging activities all
increase the rate of
erosion
Types of Erosion: Rill
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Occurs on gentle slopes of exposed soil. Water
creates small channels a few inches deep. It
may turn into gully erosion on steeper slopes.
Types of Erosion: Gully
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Occurs on steep slopes. Fast moving water
cuts deep ditches into the soil that can change
the landscape.
Types of Erosion: Sheet
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Gradual removal of
topsoil by wind or
water.
Occurs in thin
layers on very
gentle to nonsloping exposed
soils.
It can be seen by
blowing dust and
muddy water.
Types of Erosion: Mass
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Large movements
of soil due to
gravity.
Several Types:
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Landslide
Mudslide
Rockfall
Creep
Landslide
Mudslide
Rockfall
Creep
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National Geographic Mudslide Video
Induced Rockfall