Bob Flashcards
What is plucking?
- Plucking is the process in which meltwater seeps into cracks in the rocks of the valley floor/sides and freezes, becoming attached to the glacier. As the glacier advances, it pulls pieces of rock away.
When is plucking most effective?
- Plucking is most effective at the base of the glacier as the weight of the ice mass may produce meltwater due to pressure melting. It will also be significant when the bedrock is highly jointed, which allows meltwater to penetrate.
What is abrasion?
- Abrasion is the process in which, as a glacier moves across the surface, the debris embedded in the base/sides scours the surface rocks, wearing them away.
- The source material will scrape and scratch the rock. Finer material will smooth and polish the rock. Glacial debris itself is also worn down.
What is rotational scouring?
- Rotational scouring occurs when layers of rock debris accumulate on the surface of a glacier from valley sides becoming embedded within the compressed ice over successive winters. Bands of slowly rotating frozen rock are then scraped over the bedrock as the glacier moves downhill.
What type of weathering processes are more important in glaciated landscapes?
- Physical weathering factors are generally far more important in glaciated landscapes, due to the nature of glaciated landscapes
What is freeze-thaw weathering?
Freeze-thaw weathering is a process in which water enters cracks in the rock and expands by nearly 10% when it freezes, exerting a large amount of pressure on the rock, causing it to crack or split off. The more frequent the fluctuations of temperature above and below the freezing point, the more effective the process is.
What is frost shattering?
Frost shattering is a process in which, at extremely low temperatures, water trapped in rock pores freezes and expands, creating stress that disintegrates rock into small particles.
What is pressure release weathering?
Pressure release weathering occurs when the weight of overlying ice in a glacier is lost due to melting, the underlying rock expands and fractures parallel to the surface. This is significant in the exposure of subsurface rocks such as granite and is also known as dilation.
What is oxidation?
Oxidation is a chemical weathering process in which some minerals in rocks react with oxygen, either in the air or in water. It becomes soluble under extremely acidic conditions, and the original structure is destroyed.
What is carbonation?
Carbonation is a chemical weathering process in which rainwater combines with dissolved CO2 from the atmosphere to produce a weak carbonic acid that dissolves the rock over a long period, especially for rock-types like limestone.
What is hydrolysis?
Hydrolysis is a chemical weathering process in which the reaction between rock minerals and water breaks down some rocks to produce materials like clay.
What is hydration?
Hydration is a chemical weathering process in which water molecules added to rock molecules create new minerals of larger volume.
What is the role of tree roots in weathering?
Tree roots grow into cracks in the rocks and exert outward pressure, operating in a very similar way to freeze-thaw weathering.
What is organic weathering?
Organic weathering is a type of weathering caused by organic acids produced during decomposition of plant and animal litter, which cause soil to become more acidic and react with some minerals called chelation
