What are volcanoes?
Volcanoes are vents or openings in the Earth's crust through which, hot, molten rock (called magma) and gases from the interior of the Earth are released. Sometimes, but not always, the solid parts pile up around the vent to form a volcanic mountain. Some volcanoes are literally slits or holes in the ground while others are broad mountains with gentle slopes. Volcanoes in the Eastern Caribbean are mainly steep-sided and roughly conical in shape. They consist of alternating layers of solid lava (magma that has reached the Earth's surface) and broken fragments of lava called pyroclastic rocks. Since they are layered, they are called stratovolcanoes.
Why are there volcanoes in the Eastern Caribbean?
The Earth's crust is made up of slabs of material called plates which move relative to each other. The Eastern Caribbean islands lie on a plate boundary. The North American Plate, which is the denser of the two, sinks beneath the Caribbean Plate creating suitable conditions for magma to be produced. The magma then rises to the surface of the Earth where it may erupt to form a volcano. This process is called subduction and this is how the volcanic islands of the Eastern Caribbean were formed. The diagram below demonstrates the subduction process.
There are 19 'live' (likely to erupt again) volcanoes in the Eastern Caribbean. Every island from Grenada to Saba is subject to the direct threat of volcanic eruptions (see map below). Islands such as Grenada, St. Vincent, St. Lucia, Martinique, Dominica, Guadeloupe, Montserrat, Nevis, St. Kitts, St. Eustatius and Saba have 'live' volcanic centres, while other islands such as Anguilla, Antigua, Barbuda, Barbados, British Virgin Islands, most of the Grenadines and Trinidad & Tobago (which are not volcanic) are close to volcanic islands and are, therefore, subject to volcanic hazards such as severe ash fall and volcanically-generated tsunamis.