Geologist Proposes New Model To Explain Explosive Eruptions On Montserrat

October 26, 1998

When University of Cincinnati geologist Attila Kilinc calls his summertime Caribbean visit the "trip of a lifetime," he isn't recalling sandy white beaches and ice blue seas. He's recalling the moment he stepped out of a helicopter just 150 meters from the crater of the Soufriere Hills volanco that wiped out nearly two-thirds of the island of Montserrat.

On Monday, Oct. 26, Kilinc will present a new model to explain the forces which trigger the volcano's explosive eruptions during a talk at the annual meeting of the Geological Society of America in Toronto.

Ironically, Kilinc's proposed model for a trigger mechanism at Montserrat differs considerably from the model proposed by Steven Sparks, the chief scientist at the Montserrat Volcano Observatory who invited him to do field work on the island last June. Both agree that a sudden change in water concentration is behind the explosive eruptions, but neither agrees on the factors driving the change in water concentration.

Kilinc's model is based on the oxidation state of the magma. Kilinc believes the mixing of hotter basaltic magma with somewhat cooler dacitic magma lowers the oxidation state of the magma, releasing free oxygen which then combines with hydrogen in the magma to form water. The end result is the same as in Sparks' model too much water released from an oversaturated magma followed by an explosive eruption.

"Ultimately, what we dream of doing is developing a detection system of measuring the oxidation state of the magma. When it starts going down, it might be time to evacuate the area because it's going to explode," said Kilinc, emphasizing that an accurate detection system is a long way off.

University Of Cincinnati Background On The Soufriere Hills Volcano On Montserrrat

After more than 400 years of quiet, the Soufriere Hills volcano became active again in 1995. Major eruptions in 1996 and 1997 covered the southern half of the island and the capital city of Plymouth with a thick blanket of ash. The residents were evacuated safely, but it's still too hot and dangerous for them to return and rebuild because of the damage from the pyroclastic flows.

"Pyroclastic flows are fragments of rock and molten magma mixed with gases which move extremely fast and devastate everything on their path," explained Kilinc. "Many of the homes were destroyed. Almost all of them were buried to a certain level with ash. Pyroclastic flows burned everything."

The southern two-thirds of Montserrat remain an "exclusion zone" which means no one except authorized officials and scientists are allowed into the area. The lava flows reached all the way to the sea where they filled in a depression 200 feet deep.

Even when the temperature and the risk of further eruptions decreases to a point where residents can return, Kilinc said two key dangers remain. The ash can mix with rain to form muddy flows known as lahars. "This mud flow is as dangerous as the ash flow itself," said Kilinc. The other danger is the health hazard from breathing the fine particles formed when the ash blows through the air. "If it rains and the lahars are coming, they can get into their cars and get away, but they have to breathe."

Kilinc and the other researchers protected themselves with special masks, but clearly that's not a long-term solution for those faced with the long-term danger on the island of Montserrat.
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University of Cincinnati

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