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Geographic

Weathering

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2- Introduction

 - The disintegration and decomposition of rock at or near the surface of the earth.  It affects the rocks in place and no transport is involved.  This distinguishes weathering from erosion.
- Weathering takes place anywhere that water and/or air can penetrate Human processes such as pollution, which can be a large factor in acid rain,  . It produces altered material that is more stable at the Earth's surface than the original parental material, and provides the material that becomes soil or sedimentary rock. The driving forces for weathering are:
1.   Solar energy - causes circulation of the atmosphere (weather) and determines climate and vegetation.
2.   Earth's internal energy - forces within the Earth uplift deeply buried rock and expose it to weathering.
3-Rock Type and Structure-
Different rocks are composed of different minerals, and
to weathering.  For example a sandstone consisting only of quartz is already composed of a mineral that is very stable on the Earth's surface, and will not weather at all in comparison to limestone, composed entirely of calcite, which will eventually dissolve completely in a wet climate.
Bedding planes, joints, and fractures, all provide pathways for the entry of water.  A rock with lots of these features will weather more rapidly than a massive rock containing no bedding planes, joints, or fractures.
If there are large contrasts in the susceptibility to weathering within a large body of rock, the more susceptible parts of the rock will weather faster than the more resistant portions of the rock.  This will result in differential weathering


Slope - On steep slopes weathering products may be quickly washed away by rains. On gentle slopes the weathering products accumulate.  On gentle slopes water may stay in contact with rock for longer periods of time, and thus result in higher weathering rates.
Climate- High amounts of water and higher temperatures generally cause chemical reactions to run faster.  Thus warm humid climates generally have more highly
weathered rock, and rates of weathering are higher than in cold dry climates.  Example:  limestones in a dry desert climate are very resistant to weathering, but limestones in a tropical climate weather very rapidly.

Animals- burrowing organisms like rodents, earthworms, & ants, bring material to the surface were it can be exposed to the agents of weathering.