* The Caribbean Plate is a mostly oceanic tectonic plate underlying Central America and the Caribbean Sea off the north coast of South America.
* 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 seductions 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.
* Roughly 3.2 million square kilometers (1.2 million square miles) in area, the Caribbean Plate borders the North American Plate, the South American Plate, the Nazca Plate and the Cocos Plate. These borders are regions of intense seismic activity, including frequent earthquakes, occasional tsunamis and volcanic eruptions.
* Plate tectonics give rise to fold mountains, earthquakes, volcanoes, island arcs and ocean ridges. An example of an island arc is the Lesser Antilles.
* Fold Mountains are mountain ranges that are formed when two of the tectonic plates that make up the Earth's crust push together at their border. The extreme pressure forces the edges of the plates upwards into a series of folds.
* Because the plates are being created and are spreading there must be a place where they stop moving; this is the convergent margin. In this zone the advancing edge of a plate meeting another plate causes one to be driven under, often with violent consequences, creating volcanoes and earthquakes (and possibly tsunamis).
* The boundary where the Caribbean Plate meets the Cocos Plate is a fine example of a convergent and destructive margin. The result is many earthquakes and volcanoes.
* Where the destruction is less violent, small islands may form along the margin, which is usually curved and known as an island arc. The mountainous and volcanic Eastern Caribbean islands from Saba to Grenada were formed in this way.
* 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.
There are two major faults along Hispaniola, the island shared by Haiti and the Dominican Republic. This earthquake occurred on the southern fault, the Enriquillo-Plantain Garden fault system.
There hasn't been a major quake on this system for about 200 years. That means stress has been building up there for quite some time. When the strain finally grew too large, rock along the fault failed, and released a huge burst of energy in less than a minute.
Geologists are still working on the details, but it appears that 30 to 60 miles of the fault gave way. That not only triggered the original quake but has also generated more than a dozen aftershocks of magnitude 5 or higher. Those are also strong quakes, and they pose a risk to the buildings that were damaged in the original shock.
Mount Pelée, Martinique—1902
The 1902 eruption of Mount Pelée on the Caribbean island of Martinique has been called the worst volcanic disaster of the twentieth century. More than 30,000 people are thought to have died in this eruption.
The volcano had been showing signs of danger for several weeks before the main blast, producing minor earthquakes and the emission of dust and ash into the atmosphere. Many people in the surrounding villages spotted the danger signs and fled to the nearby city of St. Pierre for protection. They could have no idea what was to follow.
On the May 8, just over two weeks since the activity began, Mount Pelée erupted in dramatic fashion. A burning pyroclastic lava flow sped toward the city of St. Pierre, reaching it in under a minute, instantly destroying everything in its path. The population of 28,000 had been swollen by the influx of refugees, and almost nobody survived. On May 20 a second eruption of comparable force destroyed anything that had been left of St. Pierre 12 days earlier.