Qualibou, also known as the
Soufrière Volcanic Center, is a 3.5 × 5 km-wide
caldera
A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...
on the island of
Saint Lucia
Saint Lucia is an island country of the West Indies in the eastern Caribbean. Part of the Windward Islands of the Lesser Antilles, it is located north/northeast of the island of Saint Vincent (Saint Vincent and the Grenadines), Saint Vincent ...
that formed between 32,000 and 39,000 years ago. This eruption also formed the Choiseul
Tuff
Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock co ...
which covers the southeastern portion of the island.
The Pitons are two large
lava dome
In volcanology, a lava dome is a circular, mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions ...
s that formed before the formation of the caldera; ever since then, other domes have filled the caldera floor. There was a
phreatic eruption
A phreatic eruption, also called a phreatic explosion, ultravulcanian eruption or steam-blast eruption, occurs when magma heats ground water or surface water. The extreme temperature of the magma (anywhere from ) causes near-instantaneous evap ...
in 1766 that deposited
volcanic ash
Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, produced during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to r ...
over a wide area.
Sulphur Springs is an active
geothermal area located roughly in the center of the caldera.
In 1990, 1999 and 2000 there were shallow volcanic earthquakes located 6 km ESE of the caldera.
Gallery
Image:Sulphur_Springs_2003.jpg, Sulphur Springs
Image:Petit Piton.JPG, Petit Piton
Image:Soufrière, St Lucia, 2007.jpg, Soufrière and the Pitons
References
External links
*
Calderas of North America
Geography of Saint Lucia
Volcanoes of Saint Lucia
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