Birth Of An Island

The island of Montserrat is located in the Lesser Antilles Volcanic Arc. All of these well-known Caribbean islands are of volcanic origin: The subduction of the Atlantic tectonic plate beneath the Caribbean plate produces water-rich, bouyant magma that rises to the surface and erupts. Volcanoes form and grow over time, first beneath the sea level, then above, eventually forming the islands of the Lesser Antilles.

Map of the Lesser Antilles, a chain of islands built during millions of years of volcanic activity. Many islands of the archipelago actually feature at least one volcano that erupted in recorded history. The map is colour-coded to indicate when the most recent volcanic activity took place on each island. Credit: Jenni Barclay / Martin Mangler

Montserrat has gradually grown in this way over the last ~2.2 million years. Repeated volcanic eruptions have built the land layer by layer, pyroclastic flow by pyroclastic flow. Through time, the focus of volcanic activity has moved from the north to the south of the island. First, the Silver Hills started to emerge from the sea, with volcanic activity occurring here for more than a million years. Roughly 1 million years ago, volcanic activity in the Centre Hills began and lasted for ~700,000 years. As the focus of volcanism continued to move southwards, Centre Hills stopped erupting and activity at Soufrière Hills and South Soufrière Hills commenced ~450,000 years ago. Currently, Soufrière Hills is the only active volcanic centre on Montserrat.

View of Montserrat, the Emerald Isle, from the northeast. The currently active volcanic centre, Soufrière Hills is in the background, with earlier, now extinct volcanoes Centre Hills and Silver Hills in the foreground. Credit: Seismic Research Centre.

After activity stopped in the northern and central parts of the island, erosion from the sea and from the weather has worn down the hills, carving out ghauts and valleys, leaving the landscape that we know today.