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Montserrat Volcanic Eruptions / Soufriere Hills Volcano 

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Where is the volcano?

The Soufriere Hills volcano lies in the small Caribbean Island of Montserrat in the Antilles Islands. The Island is a British Protectorate and lies to the SW of Antiqua. The Island at its largets is no more that 12km by 8km and before the eruption had a population of 11000.

When was this eruption?

Click for bigger map. Pyroclastic Flow routes MVOThe current eruptive phase began on 18th July 1995 when large billowing clouds of ash and steam erupted from Soufriere Hills volcano in the south of the island. The eruption has left the southern two thirds of the island uninhabitable and it remains so to this day. Pyroclastic Flows still pour down the slopes of he volcano. Check out the latest eruptions at the MVO- Montserrat Volcanic Observatory

Why s there a volcano here?

Pyroclastic flows form a delta in the sea. The Soufriere Hills volcano is situated above a destructive plate margin, or subduction zone which forms the Peurto Rico Trench. Oceanic crust from the North American plate is sinking under the Caribbean plate, forming the Antilles volcanic island arc . As the slab of crust descends, sediments, water and the heat of the mantle cause the wedge of mantle above the slab to melt. The molten rock is less dense than the surrounding crust and rises to the surface . The magma formed at a depth of around 6km, with a temperature of 820–885°C, and then partially crystallised before a new injection of deep magma boosted it towards the surface.

At the surface, a thick viscous dome of lava appeared in English’s Crater in the Soufriere Hills. Most of the gas in the lava had already escaped but some remained in pockets, which caused explosive eruptions.

Montserrat volcano MVOThe volcano is a strato volcano, composed mainly of consolidated ash layers from previous eruptions. Initially pyroclastic flows flowed eastwards from the open crater down the Tar River valley, but as the dome grew, eventually flows were able to come down any side of the volcano. The flows particularly followed four main river valleys: Tar River, White River, Mosquito Ghaut and Fort Ghaut. Where the flows reached the sea they created new deltas of land e.g. Tar River valley delta.

Eruption Style

The volcano is a strato-volcano . Pyroclastic Flows and eruption columns characterise the Soufriere Hills volcano . Such flows occur when the dome collapses or explodes. Tonnes of hot rock, lava and ash explode from the crater in a fast-moving cloud. The cloud can race straight down the mountainside, or if there is a large vertical explosion, which creates an ash column, come crashing down as the ash column collapses. Such clouds have two parts: on the ground, an avalanche of large boulders and rocks, and above this a cloud of ash and gas with temperatures of 400°C+. The cloud moves at speeds of 100mph, obliterating and incinerating everything in its path.

Sequence of Events

Effects and Aftermath

Montserrats population have had their lives completely changed. Their economic,administrative and cultural capital lies in ruins like a modern Pompeii. Jobs,schools and community activities have been disrupted. At one point 5,000 people were living in temporary shelters in the north, in some cases for over two years. The north of the island had few settlements of any size and found it difficult to cope with the influx from the south. Salem is now being repopulated and is being developed together with St Johns as new population centres. The following are some of the problems :

Hazard Management

Montserrat Hazard map 1997 MVOOnce the volcano was deemed dangerous to life. Evacuaions plans and Hazard maps were put into place. The maps contained areas of increasing risk including the highest risk area- the exclusion zone. As the eruption progressed the zones were modified until the southern two thirds of the island was delcared an excluson zone.


Why not try our other Montserrat entry, World volcano section or volcanic hazards page.