The islands of the eastern Caribbean have their origins in tectonic activity.
Volcanoes erupt in the Caribbean because the area lies at the junction of a number of tectonic plates. These enormous plates, which make up the surface of the earth, are constantly moving, driven by currents within the molten rock underneath. The Caribbean plate is relatively small, and borders the North American plate, the South American plate, the Nazca plate and the Cocos plate.
Geology
Volcanic activity in the Caribbean itself, as distinct from Central America, is largely limited to the eastern Caribbean. Here, the Caribbean plate, moving approximately west to east, meets the North American plate, which is moving approximately east to west. This creates what is known as a subduction zone, where the North American plate is driven below the Caribbean plate. The rock of the North American plate melts, but as it is less dense than the molten rock of the earth's mantle, it rises, forcing its way through weaknesses in the earth's crust. The points where this molten rock appears on the Earth's surface are volcanoes.
Volcanoes
This tectonic activity has given rise to many of the islands of the eastern Caribbean. Islands such as Martinique, St. Lucia, Dominica and Grenada owe their existence to the tectonic plate boundaries of the area. According to the Global Volcanism Program at the Smithsonian Institution, the vast majority of the volcanoes of the area are known as stratovolcanoes, identifiable by their cone shape, built up by a succession of lava flows over time and the explosive nature of their eruptions.
Volcanic Eruptions
The University of the West Indies has identified seven separate volcanic disasters in the area over the past 300 years. Although the economic cost of early eruptions like those of Soufriere on St. Vincent in 1718 and 1812 is impossible to quantify, the university's Seismic Research Center estimates the economic cost of the 1902 eruptions of Soufriere and Mount Pele, Martinique, as $200 million and $1 billion, respectively. As of 2010, the most recent major eruption was that which occurred on Montserrat in 1995, which completely destroyed the capital city, Plymouth.
Volcanic Hazards
Volcanoes pose a variety of hazards to the communities of the Caribbean. The Seismic Research Center at the University of the West Indies has identified 11 different hazards associated with the area's volcanic activity. Among the most dangerous of these are pyroclastic surges, which occur when hot clouds of gasses and rock debris emitted from a volcano surge down its slopes, damaging everything in their path. In 1902, pyroclastic surges from Mount Pele in Martinique completely destroyed the town of St. Pierre, killing an estimated 30,000 people. Other hazards include lava flows, ash falls, avalanches and tsunamis.
Monitoring
The University of the West Indies' Seismic Research Center undertakes extensive monitoring of the area's volcanoes. Monitoring falls into three main categories. Volcanic activity often produces associated seismic activity, movements in the earth's crust, which can be measured by seismometers. This information can be collated and analyzed to monitor the volcano's activity. For example, seismic activity over a long period can indicate that magma or gas is moving close to the surface. Geologists also use geodesy, which measures movements in the volcano itself that might indicate that magma is rising, and analyze changes within the gases found in thermal springs on the volcano's surface to predict if an eruption is likely.
Tags: American plate, North American, North American plate, Caribbean plate, eastern Caribbean
