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.
Not only do all black people come from Africa, geneticists have asserted that ALL people originated in Africa. The reason why you'll find black Cubans as mentioned above is â¦ because of migration and more likely, slavery. 6 people found this useful.