Qualibou, also known as the Soufrière Volcanic Center, is a 3.5 × 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.

There was a phreatic eruption in 1766 that deposited volcanic ash 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.