What factors cause mechanical weathering?
Explain why chemical weathering occurs faster in hot, wet climates than in cool, dry climates.
What role does weathering play in the formation of soil?
How did settlers on the Great Plains help create the Dust Bowl?
Describe two techniques that farmers use to conserve soil.

Question

What factors cause mechanical weathering?
Explain why chemical weathering occurs faster in hot, wet climates than in cool, dry climates.
What role does weathering play in the formation of soil?
How did settlers on the Great Plains help create the Dust Bowl?
Describe two techniques that farmers use to conserve soil.

anonymous · Answer

(1) Water, mostly.  Rainfall bashes away tiny bits of whatever it hits, and in places where freezing and thawing occurs, water freezes in tiny cracks, splitting them wider, then melts and runs away, allowing more water to go in next time, and more ice to form, splitting the crack wider.  In desert areas high wind can pick up dust and sand and "sandblast" rock and soil, too, but that's a slower process.  Running water also wears down the rock and soil over which it flows.

(2) Chemical weathering implies chemical reactions, and those reactions tend to go faster at higher temperatures (because of more available energy to kick them into action).   Water also helps because it transports chemical reactants to and from the location of the reaction.

(3) Soil is largely formed from erosion (weathering) of rocks.  Quite a lot of soil is transported large distances from where it is first formed, however, by the action of rivers and streams.

(4) This is controversial, but arguably by cultvating to intensely and failing to use crop cover.  I suggest a more realistic view would blame the Dust Bowl on natural rainfall and temperature cycles, over which humans have little to no influence.

(5) Contour plowing follows the natural contours of the terrain -- the rows are always perpendicular to the slope -- so that running water is trapped and does not run off and cause erosion as easily.  The planting of ground cover in areas that are not covered by crops, and in fallow fields, keeps the soil bound in the roots of the ground cover and keeps the water from running off or evaporating easily.  Crop rotation (planting different crops each year in the same plot) tend to reduce the need for fertilizer and leaving land fallow, because different plants stress the soil (remove nutrients) in different ways.