Erosion

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Erosion

• An Examination of the Erosional Agents That Shape
  Our Land

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Main Erosional Agents

• This slideshow explores the transportation
  variances and depositional features of the four
  main erosional agents.
• Rivers
• Glaciers
• Wind
• Ocean Waves

Click on the agent to go directly to that section
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The Jobs of the Agents

• Each erosional agent will be examined in 4 ways
• General information
• Erosion
• Transportation
• Deposition

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RIVERS
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River Basics Energy and Velocity

• How much stream erosion and how much sediment is
  transported depends on the energy of the river.
• The energy of a river depends on
• The gradient (slope)
• The rivers discharge
• Channel characteristics

A braided river
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River Features
Meanders

• Meanders form as the stream gradient lowers. The
  river travels laterally across the flood plain
  forming large bends. Bends may become cut off
  (oxbow lakes) during flooding.

Edge of flood plain
Oxbow lakes
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Erosional Features

• Rivers are one of the most pervasive erosional
  agents, creating dramatic structures through
  stream abrasion.

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River Transportation

• Rivers transport sediment in three different
  ways
• Solution dissolved particles
• Suspension floating particles
• Bed Load bouncing sliding particles

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Depositional Features

• Deltas form at the end of rivers/streams as
  energy drops and sediment settles out.

Sediment plumes
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10
GLACIERS
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Glacial Basics

• A Glacier is a thick ice sheet (min. 50 m) that
  is always moving.
• Glaciers cover almost 10 of the Earths land
  surface, however they are located mostly in
  Antarctica and Greenland.
• Glaciers move about 2-5 m/day, but can move 10s
  of m/day

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Glacial Features

• Crevasses are large crack in the ice that can
  extend down 50 m.
• Icebergs form at the edge of the ice as the
  glacier meets the ocean called calving.

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2 Main Glacier Types

• Continental Found covering Greenland and
  Antarctica. Unconfined and large

• Alpine Found in mountain ranges and confined
  to mountain valleys

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Erosional Features

• As the glacier moves, sediment in the ice scrapes
  against the bedrock forming striations or groves.

Striations
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Transportation

• Glaciers transport sediment in two ways by
  rivers in the ice and by material being carried
  or pushed by the glacier.

Rock flour gives the river a green milky
appearance
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Depositional Features

• Sediment pushed to the edges of the glacier are
  called moraines.
• Terminal at the end
• Lateral to the side
• Medial in the middle

Medial moraine
Lateral moraine
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Depositional Features
Direction of ice flow

• Drumlins form as the glacier carves out the land.

Direction of ice flow
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18
WIND
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Wind Basics

• Wind is the least powerful of the erosional
  agents.
• In order for wind to be most effective, the area
  must be dry and lacking in vegetation.
• Deserts are excellent examples of such areas.

Dust storms
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Desert Features

• While most individuals think of deserts as areas
  of sand dunes only about 20 of deserts consist
  of sand. Most deserts are composed of desert
  pavement - a rocky, hard packed surface.

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Deflation forming Desert Pavement

• deflation--removal of fine-grained material by
  the wind--has exposed loose gravels mostly
  pebbles and cobbles. This makes up the majority
  of the desert surface.

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Transportation

• Most sediment is moved in the form of sand dunes.
  Sand dunes migrate through the transportation of
  sand up the gentle upwind side and deposition on
  the steeper slipface, thus sand is constantly
  recycled.

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DepositionFormation of Sand Dunes

• Dunes are created when loose sand gathers
  together due to an obstruction
• The type of dune that forms depends on
• Amount of wind
• Amount of sand
• Amount of vegetation

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Sand Dunes in the Rx Record

• The slipface of the sand dune can be preserved
  in the layers of rock

From this To this
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Types of Dunes
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OCEAN WAVES
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Wave Basics

• Energy from waves is generated by the wind.
• How much energy depends on
• Strength of wind
• Time of blowing
• Fetch area the wind blows over

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Wave Erosion

• Oceans erode the coastline through abrasion and
  wave impact.

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Sediment Transportation

• Longshore drift allows sediment to move down the
  coast line. As material is eroded from
  headlands, it can then be redistributed down the
  shore.

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Wave Depositional Features

• Waves transport material forming barrier bars and
  sandspits

Sandspit
Barrier bar
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Excellent Erosional Resources

• http//tvl1.geo.uc.edu/ice/Image/imageref.html
• http//nsidc.org/glaciers/index.html
• http//pubs.usgs.gov/gip/deserts/

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The End