November 30, 2009
Chapter 6. Weathering
Describe the role of external processes in the rock cycle. External processes include weathering which is the disintegration and decomposition of rock at or near earth's surface. Mass wasting which is the transfer of rock material downslope under the influence of gravity. And erosion, which is the removal of material by a mobile agent, usually water, wind or ice.. These are all called external processes because they occur at or near earth's surface and are powered by energy from the sun. If two identical rocks were weathered, one mechanically and the other chemically, how would the products of weathering for the two rocks differ? If the rock was mechanically weathered this means the actual breaking up of the rocks. Chemically weathering alters a rock's chemistry, changing it into different substances. In what type of environment is frost wedging most effective? Frost wedging is most effective in more freezing and moist environments. Describe the formation of an exfoliation dome. Give an example of such a feature. How does mechanical weathering add the effectiveness of chemical weathering? -Because by breaking rock into smaller pieces, the amount of surface area exposed to chemical weathering increases. Granite and basalt are exposed at the surface in a hot, wet region. a. which type of weathering will predominate? chemical weathering will predominate b. which of these rocks will weather most rapid? why? Basalt will weather most rapid because of the variations in the rock composition. Heat speeds up a chemical reaction. Why then does chemical weathering proceed slowly in a hot desert? The weathering process is more slow because a hot desert is very dry and water is by far the most important agent in chemical weathering. A hot desert wont have water.