Dominica is located in the central Lesser Antilles and occupies a land area of 750 km2. It is the most rugged island of the Lesser Antilles, being devoid of any flat land greater than 1 km2. It contains two of the highest mountains in the arc: Morne Diablotins (1,421 m) and Morne Trois Pitons (1,394 m). Dominica has 9 major peaks over 1,000 m, each with its own radial drainage systems, and the island has one of the largest river densities on Earth.
In contrast to most other islands in the Lesser Antilles arc which have one major potentially active volcanic centre, Dominica has nine, making it extremely susceptible to volcanic hazards. In fact, Dominica has one of the highest concentrations of potentially active volcanoes in the world. An unusual feature of Dominica's geology is the great abundance of young dacitic andesite domes, that form the backbone of the island. Their chemical similarity and the large volume-eruptions associated with their formation may be an indication of the emplacement of a shallow-level batholith within the arc crust under Dominica. Frequent swarms of volcanic earthquakes and geothermal activity in both south and north Dominica indicate that future eruptions are highly likely, possibly within the next 100 years.
The most recent magmatic eruption in Dominica occurred from Morne Patates, a dome within the Plat Pays volcanic complex, as recently as ~500 years ago.
The only recorded volcanic activity on Dominica were steam (phreatic) explosions in the Valley of Desolation in 1880 and 1997. The Valley of Desolation is in south-central Dominica, within a thermal area which includes the Boiling Lake - a 50 m diameter body of water that is in a constant state of boiling.
The most notable volcanic activity in Dominica is the large Roseau ignimbrite eruption, which resulted in formation of a submarine pyroclastic flow that extended over 250 km distance into the back-arc Grenada Basin, and produced co-ignimbrite ashfall throughout the North Atlantic to the east of the arc. It is the most recent large-scale explosive eruption in the Lesser Antilles arc and occurred about 28,000 years ago from the Trois Pitons - Micotrin center (Sigurdsson 1972; Carey and Sigurdsson 1980). More on:http://dominicapsn.freeyellow.com/geology.php