North Sea, the Mediterranean Sea, the Adriatic Sea and the Black Sea. The study of volcanoes is called volcanology, sometimes spelled vulcanology. This magma tends to be very viscous due to its high silica content, so it often does not reach the surface but cools at depth. They generally do not explode catastrophically. Global warming has caused a change in the pattern of the rainy seasons. It contains a tiny lagoon, which has all but dried up. It was declared a wildlife sanctuary in 1975. Investigation and expeditions to the island continue. Such settlements probably began around 1000 BC, when eastern Melanesians travelled north. During the family's years in Kentucky and Indiana, Thomas Lincoln worked as a farmer, cabinetmaker, and carpenter. Habitat destruction vastly increases an area's vulnerability