Roles of Weathering in Different Climates.

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1. Describe the roles of weathering in different climates.

Weathering is the breakdown and alteration of rocks and minerals at or near the Earth's surface into products that are more in equilibrium with the conditions found in this environment. Climate plays a role in the amount and type of weathering through solar radiation from the sun, water and temperature and wind. Most rocks and minerals are formed deep within the Earth's crust where temperatures and pressures differ greatly from the surface. Because the physical and chemical nature of materials formed in the Earth's interior are characteristically in disequilibrium with conditions occurring on the surface. Because of this disequilbrium, these materials are easily attacked, decomposed, and eroded by various chemical and physical surface processes, which vary by climate type (sun radiation, water, temperature and wind). (http://www.physicalgeography.net/fundamentals/10r.html)

Weathering is one aspect that plays a role in the geomorphic and biogeochemical processes. For example, the products of weathering are a major source of sediments for erosion and deposition in all climates, although differentially. Many types of sedimentary rocks are composed of particles that have been weathered, eroded, transported, and terminally deposited in basins. Another role of weathering is that it contributes to the formation of soil by providing mineral particles like sand, silt, and clay. Elements and compounds extracted from the rocks and minerals by weathering processes supply nutrients for plant uptake. The fact that the oceans are saline in the result of the release of ion salts from rock and minerals on the continents. Leaching and runoff transport these ions from land to the ocean basins where they accumulate in seawater. In conclusion, weathering is a process that plays a role and is fundamental to many other aspects of the hydrosphere, lithosphere, and biosphere. (http://www.physicalgeography.net/fundamentals/10r.html)

The rate of weathering is influenced by as aspects of the CLIMATE:

o Temperature
o Rate of water percolation
o Oxidation status of the weathering zone

Therefore, the type and amount of weathering is dependent on the climate, i.e., the temperature and the mean annual precipitation rates resulting in different soil moisture contents. The mean lifetime of one millimeter of different rocks into a kaolinitic saprolite is shown below.These numbers exhibit that in cold, temperate, or tropical humid zones, the climate (temperature and precipitation) controls the rate of weathering.

o Acid rocks break down differently in different climates: in tropical semi-arid (time: 65-200 lifetime years); tropical humid (20-70 lifetime years); temperate humid (41-250 lifetime years); and cold humid (35 lifetime years).
o Metamorphic rocks break down differently in climates: in temperate humid (33 lifetime years);
0 Basic rocks in temperate humid (68 lifetime years); and tropical humid (40 lifetime years).

There are three broad categories of mechanisms for weathering: chemical, physical and biological as discussed in the next question.

There are different products of weathering. For example, the process of weathering can result in the following three outcomes on rocks and minerals:

(1). The complete loss of particular atoms or compounds from the weathered surface.
(2). The addition of specific atoms or compounds to the weathered surface.
(3). A breakdown of one mass into two or more masses, with no chemical change in the mineral or rock.

The residue of ...