Qualibou, also known as the Soufrière Volcanic Center, is a 3.5 X 5 km-wide caldera on the island of Saint Lucia that formed between 32,000 and 39,000 years ago. This eruption also formed the Choiseul Tuff which covers the southeastern portion of the island.

View from Gros Piton over the Qualibou caldera
Highest point
Elevation777 m (2,549 ft)[1]
Coordinates13.838°N 61.046°W / 13.838; -61.046
Age of rock32-39,000 years
Mountain typeCaldera[2]
Last eruption1766

The Pitons are two large lava domes that formed 200 to 300,000 years ago, before the formation of the caldera; ever since then, other domes have filled the caldera floor. There was a phreatic eruption in 1766 that deposited ash over a wide area.

Sulfur 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.[3]


  1. This elevation is for Gros Piton, however Morne Gimie on the edge of the caldera has an elevation of 950 m.
  2. Global Volcanism Program, 1990. Report on Qualibou (Saint Lucia) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 15:5. Smithsonian Institution. DOI: 10.5479/si.GVP.BGVN199005-360140
  3. The University of the West Indies Seismic Research Centre (www.uwiseismic.com). "St Lucia".
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