Soufriere Hills Volcano

The Soufriere Hills Volcano is a subduction volcano located in Montserrat, West Indies. The volcano dates back to 2000 BC. The first historical eruption was in 1995, and the volcano has ever since has been ongoing.


Figure 1: This picture of the Volcano was taken by NASA's Terra spacecraft on October 12, 2009. The volcano started erupting ash we can see the plume of ash that extends westward of the island.
Figure 1: This picture of the Volcano was taken by NASA's Terra spacecraft on October 12, 2009. The volcano started erupting ash we can see the plume of ash that extends westward of the island.



Background Information

The volcano is located on an island and is over a subduction zone. Subduction zones are located by oceanic plates and are considered to be the most hazardous because the magma usually contains some water. The water creates gas bubbles and they expand rapidly under the low pressure and it results in a violent eruption. The eruptions are very explosive with high- viscosity magma generally known as pyroclastic material. This material produces ash, because as the bubbles expand and magma rises the bubbles burst into ash. The ash consists of glass that was once the walls of the bubbles, and is extremely dangerous. The first eruption was in July 1995 after a series of earthquakes, which we can call volcano-tectonic earthquakes. Volcano-tectonic earthquakes are earthquakes that can result in a volcanic eruption and are caused by the movement of magma. The earliest earthquakes on this island date back to 1933 where 723 earthquakes were recorded, but the volcano remained inactive until 1995. The volcano is a stratovolcano which means its shape is a large steep cone over a subduction zone, and also has many lava domes surrounding it. Lava domes are formed by the magma below rising and the current lava dome being replaced. Stratovolcanos are the most common type of volcanoes and have alternating layers of moderate viscosity solidified lava flow, and pyroclastic debris. This volcano has a broad range of hazards and has infrequent eruptions. The months of April to September 2009 there were small earthquakes and a small pyroclastic flow as well as mudflows. Mudflows are caused by ash and water combining together and flow at fast speeds. Mudflows are the highest cause of deaths from hazards from volcanoes. As the mud moves down slope it can gather rocks, rocks as big as cars, and it accelerates in speed. Most peopled are killed because of this reason. An interesting fact is a mudflow can be ice cold or boiling hot, and can also be called a Lahar. The volcano recently erupted last month, October 2009, and started by a series of earthquakes, then followed by ash, and five days later erupted with pyroclastic flows. The seismic activity that happen that week had 1224 rock fall signals and one volcano tectonic earthquake.

Figure 2: The Soufriere Hills volcano letting out ash.
Figure 2: The Soufriere Hills volcano letting out ash.


Volcano's Early History

The island was formed when a volcano in the Caribbean island started erupting undersea. The volcano created an undersea mountain because of the continued activity from the volcano, the mountain eventually grew over the surface of the sea creating the beginning of the island. Years later the volcano became active again with large eruptions, which created the rest of the island that we know today.

Figure 3: This map shows the different zones that the island can be classified into, which include Exclusion, Central, and Northern.
Figure 3: This map shows the different zones that the island can be classified into, which include Exclusion, Central, and Northern.



Consequences of the Eruption
The first eruption in 1995 caused major damage. The eruption caused 7,000 people to be evacuated and the rest of the residents were forced to reside in the northern part of the island. During that eruption the capital and airport were destroyed. Two years later residents on the island saw the damage of what the volcano could do. It caused dramatic changes to the landscape one day it would be a dome the next day the top is collapsed into the ocean. The magma destroyed anything and everything in its path, all the landscape was destroyed, as well as homes and schools.

Figure 4: Here is a picture of the Soufriere Hills Volcano before and after an explosion. We can see after the eruption that the top was blown off. A result of the eruption.
Figure 4: Here is a picture of the Soufriere Hills Volcano before and after an explosion. We can see after the eruption that the top was blown off. A result of the eruption.



How has the Soufrier Hills Volcano changed the island and society in the past 12 years?
The volcano has changed society in the past 12 years because it has destroyed the capital of the island, Plymounth as well as the southern half of the island which included homes and schools. The island has had to reconstruct a new capital and airport, which current resides in Little Bay. Many tourists visit Little Bay today and it is a very popular spot. The violent eruptions have resulted in the population being cut into half because the southern part of the island is considered to be unlivable, and was destroyed. The population of the island never thought this would happen, that there houses, towns, and schools would be destroyed. When the big eruption in 1995 did take place they were in shock. The residents that lived on the southern part of the island were also faced with what to do. They could not all move down to the Northern part of the island because there was not enough room. The eruption left many people homeless and at a loss of what to do next. Between the gases, ash, and rocks, the landscape of the island has been destroyed as well. The island and it population the past 14 years has been working to rebuild their homes, schools, towns, Capital, and their island. The unpredictable volcano has faced the residents and Government with many hard decisions. The Government created a hazard level system in 2008 which helps residents know the activity of the volcano.

Figure 4: Is a picture of the Hazard Level System for the island, it is currently at a level 3.
Figure 4: Is a picture of the Hazard Level System for the island, it is currently at a level 3.
Figure 5: Here is a picture of the volcano erupting at night, we can see the vibrant colors of the lava.
Figure 5: Here is a picture of the volcano erupting at night, we can see the vibrant colors of the lava.



Sources
http://www.mvo.ms/
http://news.bbc.co.uk/2/hi/science/nature/3687700.stm
http://repeatingislands.com/2009/04/05/montserrat-volcano-observatory-launches-new-website/
http://www.geo.mtu.edu/volcanoes/west.indies/soufriere/govt/miscdocs/assess121897.html
http://www.synapses.co.uk/science/mvolcano.html
http://geology.com/news/2009/soufriere-hills-volcano-eruption-image.shtml
http://www.volcano.si.edu/world/volcano.cfm?vnum=1600-05=&volpage=erupt
Hyndman, Donald; Hyndman, David: Natural Hazards and Disasters, Second Edition 2006.