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.
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.
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.
‘I love every hill and gully
Every ghaut, river and valley
She’s still my emerald city
Montserrat nice nice nice’
– Extract from Song 'Montserrat Nice' by Arrow