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 Galapagos Archipelago comprises 13 large islands, 6 small islands, 42 islets and a number of small rocks and pinnacles, which make up a total land surface of 8,000km2. The Galapagos Islands, located on the equator about 1000km (600m) west of Ecuador, were never part of mainland South America. They are a group of submarine volcanoes that grew progressively from the ocean floor, until they finally emerged above sea level about 4.5 million years ago and formed a group of islands.