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fandomhigh2005-12-02 09:31 pm
notjustacabbie.livejournal.com) wrote in fandomhigh2005-12-02 09:31 pm
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Physical geography #6
Keith is bouncing in the front of the classroom.
Weathering is the first stage in the denudation of the landscape. It is the break up of rock material on the spot. Either the physical disintegration of rock or the decomposition of minerals by atmospheric gases and water.
Mechanical weathering occurs when rock breaks into smaller pieces of the original rock. Frost wedging takes place when water in a crack freezes and forces apart the rock. Temperature changes above freezing in places like deserts may cause rocks to break apart. Tree-root wedging may widen cracks in rock. In dry climates, salt crystallization helps to break rock. Unloading of deeply buried rock by erosion of the overlying layers may also cause rock to expand upward and form joints and cracks.
Rocks weather at different rates according to mineral composition, texture, and climate. Rocks weather rapidly in hot, moist climates but slowly in dry climates.
Mass wasting is the movement of regolith downhill under the influence of gravity. Downslope movements may take the form of a slow soil creep that moves fences, posts, and house foundations. This is the most widespread and least spectacular form of mass wasting. Faster movements lubricated by water take place after heavy rain. The process speeds up when people change the landscape by adding weight to a slope, undercutting the base of the slope, or removing the natural vegetation cover.
For discussion - Imagine that you have been placed in charge of assessing the impact of acid rain on monuments in a historic cemetery in a modern industrial city. What types of monuments (i.e., what rock types) would you be most concerned about? How might you assess the degree of weathering and the rates at which it is occurring? What interventions might you recommend?
Exams are coming up soon. For revision you may find it helpful to go over this as homework.
Keith looks slightly puzzled, he's sure there used to be more students around.
Weathering is the first stage in the denudation of the landscape. It is the break up of rock material on the spot. Either the physical disintegration of rock or the decomposition of minerals by atmospheric gases and water.
Mechanical weathering occurs when rock breaks into smaller pieces of the original rock. Frost wedging takes place when water in a crack freezes and forces apart the rock. Temperature changes above freezing in places like deserts may cause rocks to break apart. Tree-root wedging may widen cracks in rock. In dry climates, salt crystallization helps to break rock. Unloading of deeply buried rock by erosion of the overlying layers may also cause rock to expand upward and form joints and cracks.
Rocks weather at different rates according to mineral composition, texture, and climate. Rocks weather rapidly in hot, moist climates but slowly in dry climates.
Mass wasting is the movement of regolith downhill under the influence of gravity. Downslope movements may take the form of a slow soil creep that moves fences, posts, and house foundations. This is the most widespread and least spectacular form of mass wasting. Faster movements lubricated by water take place after heavy rain. The process speeds up when people change the landscape by adding weight to a slope, undercutting the base of the slope, or removing the natural vegetation cover.
For discussion - Imagine that you have been placed in charge of assessing the impact of acid rain on monuments in a historic cemetery in a modern industrial city. What types of monuments (i.e., what rock types) would you be most concerned about? How might you assess the degree of weathering and the rates at which it is occurring? What interventions might you recommend?
Exams are coming up soon. For revision you may find it helpful to go over this as homework.
Keith looks slightly puzzled, he's sure there used to be more students around.