GEOLOGIC HISTORY
The Qualibou caldera on the SW side of St. Lucia
provides the setting for the Pitons, two steep-sided
pre-caldera lava domes that form one of the scenic
highlights of the West Indies. The 3.5 x 5-km-wide
Qualibou caldera formed about 32-39,000 years ago in
conjunction with the eruption of the Choiseul Tuff .
Numerous resurgent post-caldera lava domes fill the
caldera floor. The latest magmatic eruptions accompanied
formation of the Belfond lava dome (radiocarbon dates of
20,900 to 34,000 years before present). The only known
Holocene activity was a minor phreatic eruption in the
sulfur Springs thermal area in 1766 AD that ejected a
thin ash layer over a wide area.
Historic Activity:
- Qualibou caldera is the youngest volcanic center in
St. Lucia and its last eruption is thought to have been a
phreatic explosion in 1776.
Recent Activity:
- Present-day activity at the caldera is limited to hot
springs and solfataras. Earthquake swarm in May 1990
located 6 km ESE from caldera.
Data Sources:
- Global Volcanism Network (V. 15, No. 5).
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