Shale is a fine-grained sedimentary rock that forms from the compaction of silt and clay-size mineral particles that we commonly call mud.This composition places shale in a category of sedimentary rocks known as mudstones.hale is a rock composed mainly of clay-size mineral grains. These tiny grains are usually clay minerals such as illite, kaolinite and smectite. Shale usually contain other clay-size mineral particles such as quartz, chert and feldspar.
Extremely draught resistant Opuntia cactuses form arid shrub forests in the lowlands, particularly on the larger islands, like Santa Cruz. At higher elevations, the climate of the Galapagos Islands, Ecuador, is cooler and with more rainfall. As a result there is true forest on the higher mountains thanks to the cooling of the air as it is forced up. When the air cools off, the humidity in the air condenses, thus forming clouds.
The predominance of reptiles is one of the most striking things about the wildlife of the Galapagos Islands. Mammals, after all, tend to be the dominant large terrestrial life form in almost every other part of the world. The hot and dry conditions found throughout the islands for much of the year provide ideal habitat for reptiles to thrive.