Brown University News Bureau

The Brown University News Bureau

1997-1998 index

Distributed August 28, 1997
Contact: Linda Mahdesian

Measuring Montserrat

Brown geologist develops technique to measure velocity in volcanoes

Brown geology professor Malcolm Rutherford has developed a way to measure the rate of volcanic eruptions, which he applied in the case of Montserrat.

PROVIDENCE, R.I. -- Can scientists predict when a dormant volcano will erupt? Not yet, but now scientists can assess whether an active volcano is becoming a dangerous volcano, as in the case of Montserrat in the Caribbean. Three years ago, Brown geology professor Malcolm Rutherford developed a technique to measure the rate of eruption. He began using that technique on the Montserrat volcano in July 1995 when modern-day eruptions began and showed that the volcano was increasing in intensity Prior to that, the volcano had lain dormant for nearly four centuries.

Rutherford developed a way to analyze cooled chunks of magma, or lava, to measure the rate of eruption. Using samples from the Mount St. Helens eruptions in the 1980s, Rutherford found that magma rocks dotted with partially decomposed black minerals called hornblende were present when the eruptions were slow. These rocks were heavy and dense because gas bubbles in the magma had time to escape. Lightweight, honey-combed rocks full of gas bubbles resulted from faster, more explosive eruptions.

Rutherford and Joe Devine, a research scientist at Brown, received a grant from the international arm of the National Science Foundation in 1995, to study the sleeping volcanoes on Montserrat and Nevis, the island to the north of Montserrat. Their original intention was to study the volcanoes' history and compare rock samples there with the composition of rocks from Mount St. Helens. By sheer serendipity, Devine arrived in the Caribbean in June of 1995, a month before the first eruptions on Montserrat. The geologists had an active volcano on which to test their new technique. By analyzing magma rock samples, Rutherford and Devine were able to show that the rate of eruption was increasing with time - and thus the situation for the island dwellers was becoming more dangerous.

By the spring of 1996, their samples showed that an explosive eruption was likely. In September of that year the first explosive eruptions occurred, spewing gas, ash and rock at nearly 100 miles an hour at temperatures between 800 and 900 degrees Centigrade. Towns and terrain in the surrounding areas were devastated. Devine, who had the risky job of collecting samples, was quoted in the July 1997 issue of National Geographic as saying, "I didn't waste any time there. It was get in, get out, and thank your lucky stars." He has visited the island eight times during the last two years and presented his findings to authorities monitoring the volcano.

Since the fall of last year, thousands of Montserratians have been evacuated, as the volcano has cycled from effusive (slower) eruptions to explosive ones. Thus far, according to Rutherford, the eruptions have been on a smaller scale than those of Mount St. Helens, which continued to erupt from 1980 to 1986. The most explosive eruptions of Mount St. Helens occurred in the first 12 hours. The Mount Pinatubo volcano in the Philippines, which erupted in 1991, eclipsed both Mount St. Helens and Montserrat combined. "If Mount St. Helens spewed enough lava to cover the state of Rhode Island with six inches of material, Pinatubo was 10 times that big," Rutherford said.

To contact Malcolm Rutherford, call 401/863-1927. For Joe Devine, call 401/863-2560.