The park was established in 1975 and was designated a UNESCO World Heritage Site in 1997. Its area is about , and it is dominated by the Morne Trois Pitons volcanoes (), from which it gets its name. The three major types of geological formations found in the park are volcanic cones, glacis slopes, and soufrières (sulphur deposits). The landscape consists of steep-sided volcanic hills separated by deep canyons. All the major waterways of the southern half of the island emanate from here, and there are spectacular waterfalls, creeks, rivers, pools, and natural lakes. Ongoing volcanic activity is demonstrated by the fumaroles and hot springs, geysers, mud pools, and streams of various colours. The Boiling Lake is a water-filled fumarole with a temperature of near the edge and a hotter centre, where boiling water churns up from the depths.