Chemical weathering is the process by which rocks are broken down by chemical reactions. There are different types of chemical weathering. Hydrolysis is the chemical breakdown of a substance when combined with water. The most common example of hydrolysis is feldspar in granite rocks changing to clay.
Racially Africans originated in Africa, Europeans in Europe and so on. (before that the human species originated in Africa, but that's ancient history) African Americans are an ethnic group, or a subrace of the African race.
Australian/Irish/European. Alonzo: The fact that North Africa is part of Africa does not make it African as the fact that the Middle East/Caucasus is in Asia does not make it Asian, since the demography and history of both areas is closely connected to Europe.