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.

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_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?

http://www4.uwsp.edu/geo/faculty/ritter/geog101/textbook/mass_movement_weathering/water_erosion.html

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?

http://www4.uwsp.edu/geo/faculty/ritter/geog101/textbook/mass_movement_weathering/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_weathering/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.htm