Erosion

Erosion

Rain

• Splash• Sheet• Rill• Gully

Heavy rains in northwest Iowa washed away soil, leaving this scarred tableau. This type of erosion, termed sheet-

and-rill 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.



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_weathering/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?




Rain – Rill Erosion• Water collects into closely-

spaced small channels• Tend to form on steeper land

What might happen to rills if they aren’t stopped?




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?




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

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.



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.



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.



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.htm



Erosion

Documents

wind erosion

type of erosion

moving water

water waves

scrape rocks sediment

thempluck rocks sediment

groundlarge flow of

sheets of surface water