Geomorphic processes

• Oxidation


  Chemical Weathering;

  When materials react with oxygen either in air or water, causing the original structure to be destroyed.
• Carbonation


  Chemical Weathering;

  the mixing of rainwater with carbon dioxide from the atmosphere to make a weak carbonic acid, causing rock to slightly dissolve.
• Nivation


  Combination of freeze-thaw action, solifluction, transport by running water and possibly chemical weathering.

  Responsible for initial enlargement of hillside hollows.
• Hydrolysis 


  Chemical weathering;

  reaction between rock minerals and water;

  silicates combine with water, which produces secondary minerals.
• Hydration


  Chemical weathering;

  a form of chemical weathering in which the chemical bonds of the mineral are changed as it interacts with water.
• Solution


  Chemical weathering;

  any process by which a mineral dissolves in water is known as solution (though mineral specific i.e. carbonation can be identified)
• Freeze-thaw

  Mechanical weathering;

  water enters cracks/joints and expands by nearly 10% when it freezes;

  this exerts pressure onto the rock, which causes it to split or break.
• Frost shattering


  Mechanical weathering;

  water trapped in rock pores freezes and expands;

  creates stress which disintegrates rock to small particles.
• Pressure release


  mechanical weathering;

  weight of overlying ice in a glacier is lost due to melting, the underlying rock expands and fractures parallel to the surface;

  exposure of sub-surface rocks such as granite and is also known as dilatation.
• Tree roots

  Biological weathering;

  grows in cracks or joints in rocks and exert outward pressure;

  when trees topple, their roots can also exert leverage on rock and soil, bringing them to surface and exposing them to further weathering.
• Organic acids

  biological weathering;

  produced during decomposition of plant and animal litter cause soil water to become more acidic and react with some minerals (chelation).
• Rock fall

  Mass movement;

  on slopes of 40 degrees or more, rocks may become detached from the slope by physical weathering processes;

  fall to foot of the slope under gravity.
• slides


  mass movement;

  may be linear, with movement along a fault or bedding plane with movement along a curved or slip plane.
• abrasion

  Debris embedded in its base/sides scours surface rocks, wearing them away (i.e. sandpaper);

  coarse material will scrape, scratch and groove the rock;

  finer material will tend to smooth and polish the rock.
• Glacial debris worn down in abrasion is called rock flour.
• Plucking


  The glacier freezes onto and into rock outcrops at the base of the glacier;

  movement of the ice pulls away (i.e. plucks) pieces the rock;

  leaves jagged landscape.
• Aeolian deposits

  Transportation;

  fine material carried and deposited by wind, often blowing across outwash deposits.
• Rockfall;

  transportation;

  Weathered debris falls under gravity from the exposed rock above the ice down onto the edge of the glacier.
• Avalanches

  transportation;

  often contain rock debris within the snow and ice that move under gravity.
• Debris flows

  Transpiration;

  In areas of high precipitation and occasional warmer periods, melting snow or ice can combine with scree, soil and mud.
• abrasion


  Transportation;

  Smaller material worn away from valley floors and sides.
• plucking

  transportation;

  large rocks plucked from the side and base of valleys, deposited later on.
• Volcanic eruptions


  transportation;

  a source of ash and dust.
• supra-glacial

  on the surface of the glacier
• en-glacial

  within the ice of the glacier
• sub-glacial


  at the base of the glacier.
• Glacial deposition

  when ice melts at the snout which deposits its sediment;

  When the glacier change between compressing and extending flow;
• Outwash is a material deposited by meltwater.
• Till is angular, unstratified and unsorted rocks, clay and sand deposited by ice.
• Lodgement till is from advancing ice
• Ablation till is from melting ice