"I've never stopped speaking to rocks"

What Valentin Trolls calls the magic moment occurred in the mid-90's at the Julius Maximilians University in Würzburg, Germany. His initial scepticism towards the course in geophysics and geology turned into fascination of how geologists were able to read rocks and minerals.

“Unlike my studies in physics, in geology there were objects I could touch, ask questions of and find answers by observation. It made a huge difference," says Valentin Troll.

The rock that made such a great impression on him, an ignimbritic rhyolite, is formed by volcanic explosions, apparent in the little flames of pumice stone within the structure of the rock. In his mind, Valentin Troll could suddenly see whole series of processes, several hundred million years old, passing by.

“From that day on, I was hooked on this rock business!”

The scientific name for his field of research is petrology, which studies the origin, development and use of rocks. Valentin Troll specialises in identifying processes inside volcanoes based on the erupted rocks and the minerals within. Volcanic rocks are formed when molten rock, or magma, crystallises different minerals on its journey through the Earth. Whether the magma begins to move through the volcano and penetrate through the Earth's surface depends on the interaction of a variety of chemical and physical processes.

“Volcanoes are subject to both internal and external driving forces and I believe that the behaviour of a volcano depends very much on the volcano’s character and its external influences, such as the environment it is located in. Volcanoes that are situated in areas with a lot of limestone tend to be especially explosive. It’s likely because of extra CO2 being released from the limestone by magmatic heating and magma-limestone interaction,” says Valentin Troll.

Together with his research team, he visits both extinct and active volcanoes around the world. His work has brought him to volcanic regions that extend over several hundreds of kilometers, such as in the Indonesian archipelago. One of these volcanoes, Mount Agung in Bali, appeared to come to life again in November 2017, but the large eruption never came. A potential calm before the storm, according to Valentin Troll.

“As is so often the case, these large volcanoes grow a bit nervous but then settle down again, only to wake up once more a few months later.”

He remains in contact with colleagues and authorities at the scene; a collaboration going back some ten years. As recent as September 2017, Valentin Troll was on a lecture tour to several Indonesian universities. But predicting volcanic eruptions is an expensive and difficult task, which has taken a back-seat due to the country's social and economic challenges.

“It’s a huge country with huge population growth. There’s also a conflict with Malaysia over oil fields, they have rebel groups fighting in different areas of the country, an HIV problem, and so on. Volcanoes are a small issue to them. Therefore, they won’t put a large percentage of their national finances into volcano research.”

However, there are positive signs. Financial assistance from, among others, Sweden and international research collaborations, have given Indonesia a better position to assess the risks associated with volcanic threats.

The work of Valentin Troll and his colleagues focuses on chemical analysis of rocks and minerals as well as gas and petrology experiments.

“We measure the increased heat and gas flux from the volcanoes and look for for uplift and subsidence caused by eartquakes and seismic activity. Nowadays we also use remote sensing, to check for example if the volcano is deforming. This can be measured by satellites each time they pass by, and you can see whether the volcano has been inflating, which it often does before eruption,” says Valentin Troll.

“The more converging parameters we can identify, the greater a chance we can predict an eruption within a day or two. But it’s not easy.”

His office at the Department of Earth Sciences is lined with rocks and minerals from expeditions around the world, one specimen more evocative than the other. They have been hacked out of volcanoes like Indonesian Agung and Merapi using tools reminiscent of those used by historical geological expeditions: cutter, hammer and chisel. Back at the laboratory at the Geocenter however, the samples are examined by the most modern of research instruments. Analyses of volcanic crystals can be performed at the nano-scale by use of an electron microprobe. That way, scientists can identify changes in the activity level of volcanoes hundreds of years back, or just recently.

“Sometimes we see that there have been earthquakes that have interrupted the volcanic eruption or for example that there has been an influx of new magma arriving in the volcano, so that the chemistry has changed," says Valentin Troll. “Since all these processes are recorded in the volcanic rocks and crystals, we can put them in an interpretation framework, which we can then scale up, and say something useful about volcanic phenomena.”

The passion for rocks is still his biggest motivator, as well as the hope that increased knowledge of volcanic processes will be useful for society.

“In school, I was taught that rocks are isolated systems. Today, with all my training from interacting with rocks, my big desire is to be able to change those kinds of outdated views. I hope to be able to reach out with information about how important and useful knowledge of petrology is for all of us, from ore deposits to volcanic hazards and geothermal activity.”

When asked what advice he would give to students who are interested in his field, Valentin Troll doesn’t hesitate for an instant.

“Listen to the rocks...”

2018-02-06