Facts

Were the mountains of the Land of Nephi left when the land sunk in the sea? Well…highest elevation of each island. Most of these were volcanoes.

Stone carving of a man who is fleeing calamity in a boat…volcanoes, earthquakes, drawings.

Space Shuttle photo 052-0074-0007 looking northwest across the volcanic arc of the Lesser Antilles. Barbados is in the foreground. The distance from Guadeloupe to Grenada is about 200 km. Photo taken on October 23, 1992.

The volcanoes of the West Indies result from the subduction of oceanic lithosphere, created at the Mid-Atlantic Ridge, beneath the east edge of the Caribbean Plate. The volcanoes of Central America are the result of subduction of the Cocos Plate beneath the west edge of the Caribbean Plate. Arrows show the direction of plate motion. Black "teeth" are on the overriding plate at subduction zones.

Earthquake fault lines in the Caribbean

If new oceanic lithosphere is created at mid-ocean ridges, where does it go? Convection cells in the mantle help carry the lithosphere away from the ridge. The lithosphere arrives at the edge of a continent, where it is subducted or sinks into the asthenosphere. Thus, oceanic lithosphere is created at mid-ocean ridges and consumed at subduction zones, areas where the lithosphere sinks into the asthenosphere. Earthquakes are generated in the rigid plate as it is subducted into the mantle. The dip of the plate under the continent accounts for the distribution of the earthquakes. Magma generated along the top of the sinking slab rises to the surface to form stratovolcanoes.

A mechanism to move continents when heat trapped in the Earth caused convection currents, areas where fluids beneath the Earth's crust rise, flow laterally, and then fall. The currents and solid rock would rise beneath continents, spread laterally, then plunge beneath the oceans.

Geologist Harry Hess proposed that new ocean floor is formed at the rift of mid-ocean ridges. The ocean floor, and the rock beneath it, is produced by magma that rises from deeper levels. Hess suggested that the ocean floor moved laterally away from the ridge and plunged into an oceanic trench along the continental margin.

Puerto Rico Trench
A trench is a steep-walled valley on the sea floor adjacent to a continental margin. For example: the Caribbean Plate and the North American Plate, an oceanic ridge into the Atlantic Ocean. In Hess' model, convection currents push the ocean floor from the mid-ocean ridge to the trench. The convection currents might also help move the continents, much like a conveyor belt.

Robert Dietz independently proposed a similar model and called it sea floor spreading. Dietz's model had a significant addition. It assumed the sliding surface was at the base of the lithosphere, not at the base of the crust. Continents are no longer thought to plow through oceanic crust but are considered to be part of plates that move on the soft, plastic asthenosphere. A driving force, convection currents, moved the plates.

Earthquakes, volcanic eruptions, volcanic island flank failures and underwater slides have generated numerous destructive tsunamis in the Caribbean region. Convergent, compressional and collisional tectonic activity caused primarily from the eastward movement of the Caribbean Plate in relation to the North American, Atlantic and South American Plates, is responsible for zones of subduction in the region, the formation of island arcs and the evolution of particular volcanic centers on the overlying plate. The inter-plate tectonic interaction and deformation along these marginal boundaries result in moderate seismic and volcanic events that can generate tsunamis by a number of different mechanisms. The active geo-dynamic activities have created the Lesser Antilles, an arc of small islands with volcanoes characterized by both effusive and explosive activity. Eruption mechanisms of these Caribbean volcanoes are complex and often anomalous. Collapses of lava domes often precede major eruptions, which may vary in intensity. Locally catastrophic, short-period tsunami-like waves can be generated directly by lateral, direct or channelized volcanic blast episodes, or in combination with collateral air pressure or cascading debris avalanches. Submarine volcanic caldera collapses can also cause local destructive tsunami waves.

Volcanoes of the Eastern Caribbean Island Arc (Web graphic of West Indies University)
Volcanoes in the Eastern Caribbean Region have unstable flanks. Destructive local tsunamis may be also generated from volcanic flank failures, which may be triggered by volcanic episodes or simply by an unstable sea floor. The following brief report describes recent volcanic episodes in the Eastern Caribbean and the tsunami or the tsunami-like waves which were generated. More specifically, the report recent volcanic eruptions of the Soufriere Hills volcano on Montserrat, of Mt. Pelée on Martinique, of Soufriere on St. Vincent and of the Kick'em Jenny underwater volcano near Grena.