By Chris Bryant
Photos by Matthew Wood
Geologists frequently study rocks formed hundreds of millions of years ago.
For The University of Alabama’s Dr. Kim Genareau, her interests lie in those formed last Friday.
Ok, so that’s a slight exaggeration, but, in comparison to the time stamps on which many of her departmental peers’ focus, it’s a close approximation.
Genareau is a volcanologist – a geologist specializing in the study of volcanoes. In one project, she focuses on the 2010 eruption of the Merapi Volcano in Java, Indonesia. She’s analyzing material birthed by that eruption and deposited along the mountain’s flanks.
Using sophisticated laboratory techniques – both in UA labs and at Arizona State University – Genareau and her students analyze volcanic deposits in hopes of better understanding some of the geological and chemical conditions present at the time of the devastating eruption.
In her UA laboratory, dozens of tiny plastic bags filled with stony deposit nuggets – categorized by their size as lapilli – are labeled and stored.
Through analyses of these deposits as well as volcanic ash, also retrieved from the site, Genareau can home in on the ratios of lithium to silicon, for example, found within the samples and unravel the role fluorine may have played during and between eruptions. She’s also interested in what influences water and carbon dioxide had on the system’s dynamics.
“We’re analyzing what those different elements were doing in order to understand what caused the activity to be so violent,” Genareau says.
And, devastatingly violent the 2010 eruption was. Numerous massive, ground-hugging clouds, containing liquidized blends of hot rock fragments and gases, raced down the volcano’s sides and into neighboring villages, sometimes at speeds of more than 90 miles per hour.
These clouds, known by scientists as pyroclastic flows, traveled several miles, killing more than 350 people, destroying multiple villages and resulting in the evacuation of more than 250,000. Temperatures within the clouds were estimated at up to 500 degrees F.
The 2010 event was one of Mount Merapi’s largest eruptions of the last 100 years, Genareau says. The volcano, whose named loosely translates as “Mountain of Fire,” has erupted regularly since 1548.
But, the 2010 eruption was different.
“It began in a unique fashion with an explosion,” Genareau says. “It’s difficult to tell why eruption styles change. But, you always learn something new whenever there is an eruption.”
Traditionally, Mount Merapi’s eruptions begin with the collapse of a viscous lava dome, not a sudden explosion.
Two violent eruption sequences occurred 10 days apart in 2010. The second, on Nov. 5, was particularly large. By analyzing samples deposited on both of those violent eruption days and on almost a daily basis in between, Genareau gains insight to what was happening inside the volcano during this stretch.
In one key finding, published by the Geological Society of London, Genareau and her co-authors concluded that the initial explosion, on Oct. 26, destabilized the lava dome – magma that had earlier erupted and then piled around the conduit. This clearing of the conduit – the opening that carries magma from the volcano’s core up to its mouth, or vent – enabled the more volatile juvenile magma to rise. This helped generate, in coming days, the more violent pyroclastic flows that would follow.
The researchers also found evidence of the build-up of lithium within the Oct. 26 lava dome. This, Genareau says, indicates a prolonged period of gas accumulation within the volcano, a contributor to the overpressure present prior to the initial 2010 explosion.
“If a volcano suddenly does something different, it is important to understand why.”
Through the use of scanning electron microscopy, secondary ion mass spectrometry, and electron probe microanalyses, the UA scientist is beginning to answer some of those whys.
Genareau, who has taught at UA since 2013, earned her doctorate in geological sciences from Arizona State University and holds bachelor degrees in geology, physics and philosophy.
By better understanding the causes of eruptions, volcanologists hope to more accurately forecast volcanic eruptions. It remains an elusive goal, but time, and enquiring minds, can help.
“Every eruption,” Genareau says, “provides new information to help us better understand volcanoes.”
Dr. Genareau is an assistant professor of geological sciences in UA’s College of Arts and Sciences. This portion of her research is funded by a $114,000 grant from the National Science Foundation.