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Geologic Settings

The Earth's surface consists of several huge crustal plates. Earthquakes and volcanic eruptions take place at the boundaries of these plates. Kick'em Jenny submarine volcano is located in the Lesser Antilles arc, and the Caribbean plate boundary is shown as the white dotted line in the figure. This volcanic arc marks the eastern boundary of the Caribbean plate, where the floor of the North Atlantic is sliding down beneath or subducting under the Caribbean plate.

Figure 1

The Lesser Antilles Island Arc

Figure 2   The string of islands known as the Lesser Antilles stretches from the margin of the South American continent to the Anegada Passage in the north, which marks the boundary with the Greater Antilles Figure 2. The island arc is about 850 km in length and there are a number of active volcanoes present. These islands have been built up almost entirely by volcanic eruptions, first on the sea floor as submarine volcanoes or seamounts, and later to emerge and grow as volcanic islands. There are at least five islands which currently have active volcanoes, that is volcanoes which have had historic eruptions (post-Columbus). The northernmost young volcano in the Lesser Antilles is Saba, but it has not been active in historic time. To its south lies the island of St Eustatius, with the Quill volcano at its southern end, and its activity is also pre-historic in origin. Similarly, the Mount Misery (Liamuiga) volcano on the island of St Kitts is also inactive, and so is the Nevis Peak volcano on the near-by island of Nevis. Figure 3Further south is the island of Montserrat, where the Soufriere Hills volcano has been in a constant state of activity since 1997, forcing evacuation of much of the island. The Soufriere volcano on the French island of Guadeloupe had minor steam explosions in 1976, and must be regarded as an active volcano. Further south, the island of Dominica has a number of volcanic centers, but no current activity except for the Boiling Lake. Just south of Dominica is Martinique, with its ill-fated volcano Montagne Pelee, which had a devastating eruption in 1902, killing over 29,000 people, and erupted again in 1929-32. The near-by island of St Lucia has an active hydrothermal field in the Qualibou caldera, but no current volcanic activity is known. South of St Lucia is the Soufriere of St Vincent, a volcano that has erupted violently in 1902, and erupted again in 1971 and 1979. The southernmost active volcano in the Lesser Antilles arc is the submarine volcano Kick’em Jenny.
Figure 4The Lesser Antilles are formed where two great crustal plates collide  Figure 3. The North American plate (right) moves steadily to the west, subducting beneath the Caribbean plate. Each plate is about 100 km in thickness and they move at a rate of about 2 cm per year. The interaction of the plates results in earthquakes (blue, yellow and red dots) and the formation of magma or molten rock (red) that rises upwards to erupt and form the Lesser Antilles volcanic islands.
The subduction process introduces water to great depths in the Earth and this leads to melting of rocks in the Earth’s mantle, producing the liquid rocks or magmas that erupt to form the volcanoes at the surface above Figure 4.