EROSIONAL PROCESSES

T Parson – Allerton Grange

AbrasionAbrasion is scraping of a rock surface by friction between rocks and moving particles during their transport in wind, glacier, waves,

gravity or running water – essentially a sandpapering action.The intensity of abrasion depends on the hardness, concentration,

velocity and mass of moving particles.

http://www.uky.edu/AS/Geology/howell/goodies/elearning/module07swf.swf

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Task : Abrasion

Using a flow diagram (text or

diagrams) describe and explain the process of plucking

The glacier moves slowly across the landscape

?

?

Use as many boxes as you need, remember the more

detail the better !

Plucking

Plucking, in the sense relating to glaciers, is when a glacier erodes away chunks of bedrock to be later deposited. Glacial plucking

exploits pre-existing weaknesses in the bedrock. When the ice comes into contact with a joint, the friction on the ice results in melting of

some of the ice. The ice then refreezes within the rock fracture. This is then followed by the entrainment of the loosened rock by the ice. The glacier moves ‘plucking’ the loosened material. Plucking is also

known as quarrying.

http://www.geocities.com/CapeCanaveral/7639/land/pluckng.htm

Task : Plucking

Using a flow diagram (text or

diagrams) describe and explain the process of plucking

There are faults, cracks or areas of weakness in the rock

?

?

Use as many boxes as you need, remember the more

detail the better !

Freeze-thaw actionThis process can also be called frost shattering. Common in areas where the climate fluctuates around freezing point. Moist soils expand or frost heave upon freezing as a result of water migrating along from unfrozen areas via

thin films to collect at growing ice lenses.

Pore spaces expand as liquid is attracted from surrounding pores. This pressure is exaggerated with the process of freezing/thawing, putting

pressure on the surrounding rocks.

http://www.uky.edu/AS/Geology/howell/goodies/elearning/module07swf.swf

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Freeze induced weathering action occurs mainly in environments

where there is a lot of moisture, and temperatures frequently fluctuate above and below freezing point—

that is, mainly alpine and periglacial areas. An example of rocks

susceptible to frost action is chalk, which has many pore spaces for the growth of ice crystals. This process can be seen in Dartmoor where it

results in the formation of tors. The splitting of rocks along the joints

into blocks is called block disintegration. The blocks of rocks that are detached are of various

shapes depending on rock structure.

Freeze-thaw action continued…

http://youtube.com/watch?v=PMDXJlC-c-w&feature=related

http://www.geography.ndo.co.uk/animationsweathering.htm#

http://www.bbc.co.uk/schools/gcsebitesize/geography/glaciation/glacialprocessesrev2.shtml

Task : Freeze – thaw weathering

Using 4 diagrams describe and explain freeze – thaw

weathering

A rock fills with water as the climate is

moist, the temperature is above

freezing.

NivationNivation is the process of alternative freeze and thaw by which fallen snow gets converted into ice or Névé. When the neve is large enough

to move it becomes a glacier. Other erosion processes may occur beneath the snowpatch.

Task : Nivation

Describe nivation in three sentences

Slide 2/4 – drawing needs re-doing

http://www.flickr.com/photos/deego/1091977848/ - Slide 6/7 picture

http://www.flickr.com/photos/dougmcneall/2512553556/ - Slide 8 picture

http://www.flickr.com/photos/davejglaves/1103055883/ - Slide 8 picture

http://www.flickr.com/photos/35127493@N00/114072481/ - Slide 10 picture