Transcript Types of Erosion - science

Erosion
Rain
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Splash
Sheet
Rill
Gully
Heavy rains in northwest Iowa washed away soil, leaving
this scarred tableau. This type of erosion, termed sheet-andrill erosion, occurs when there is insufficient vegetation to
hold soil in place. As rain falls, it forms sheets of surface
water that transport soil away. As more water accumulates,
it forms runoff channels called rills, which further displace
soil.
http://science.nationalgeographic.com/science/photos/weathering-erosion-gallery
Water Runoff
• 40% of precipitation becomes
runoff
• Water carries weathered rocks
and sediment
What factors might affect runoff?
A waterfall fed by glacial runoff tumbles over
sheer cliffs and into the turquoise water of
Admiralty Inlet on Baffin Island, Nunavut,
Canada. Such moving water is among the most
powerful of nature's landscape-altering tools.
http://science.nationalgeographic.com/science/photos/weathering-erosion-gallery
Rain – Splash Erosion
• Falling raindrops make small
craters on ground
Describe how a raindrop causes the
soil to move.
http://www4.uwsp.edu/geo/faculty/ritter/geog101/textbook/mass_movement_wea
thering/water_erosion.html
Rain – Sheet Erosion
• Occurs when water can’t soak
into the ground
• Large flow of water over land
What might help prevent sheet
erosion?
http://www4.uwsp.edu/geo/faculty/ritter/geog101/textbook/mass_movement_wea
thering/water_erosion.html
Rain – Rill Erosion
• Water collects into closelyspaced small channels
• Tend to form on steeper land
What might happen to rills if they
aren’t stopped?
http://www4.uwsp.edu/geo/faculty/ritter/geog101/textbook/mass_movement_wea
thering/water_erosion.html
Rain – Gully Erosion
• Steep-sided trenches
• Formed when rills come
together
• Difficult to stop
Why do you think it is so difficult to
stop gully erosion once it has
started?
http://www4.uwsp.edu/geo/faculty/ritter/geog101/textbook/mass_movement_wea
thering/water_erosion.html
Water – Waves
• Moves sand from beach to
sandbars
What types of events might increase
erosion on beaches?
The 367-mile-long Texas gulf coastline
loses around 235 acres of lands to
erosion each year, equivalent to more
than 181 football fields of beach,
according to the Texas General Land
Office.
http://www.window.state.tx.us/comptrol/fnotes/fn0712/coast.html
Water - Waves
• Not just on the beach….
Why is this type of erosion so
dangerous to humans?
Sandbars swirl beneath Oregon Inlet in
Cape Hatteras National Seashore on
North Carolina's Outer Banks. Waves
driven by ocean winds can cause the
sandbars here to shift and change
literally by the hour.
http://science.nationalgeographic.com/science/photos/weathering-erosion-gallery
Wind
• Moving air
• Blows loose sediment
• Carries abrasive particles
Where do you think wind erosion
might be most common?
Wind erosion makes these layered sandstone
hills swirl in Paria Canyon-Vermilion Cliffs
Wilderness Area. The area, whose 112,500 acres
straddle the Utah-Arizona border, is home to
sandstone arches, huge red rock amphitheaters,
and hanging gardens.
http://science.nationalgeographic.com/science/photos/weathering-erosion-gallery
Glaciers
• Larges masses of moving ice &
snow
• Push & carry rocks and sediment in
front of them
• “Pluck” rocks & sediment from the
land beneath them.
• Scrape rocks & sediment from valley
walls.
What do you think happens to the
valley as a glacier moves through it?
The Bernard Glacier in Alaska's Saint Elias
Mountains looks like a huge alpine highway.
Glaciers are slow but highly effective shapers of
the land, essentially carrying away anything in
their path—from soil and rocks to hills and even
the sides of mountains.
http://science.nationalgeographic.com/science/photos/weathering-erosion-gallery
Mass Wasting
• Process by which rock and soil
move down a slope
• Usually as a mass
• Under the force of gravity
What types of events would be
considered mass wasting?
http://geology.campus.ad.csulb.edu/people/bperry/Mass%20Wasting/Prevention_of_Mass_Wasting.ht
m