Talks at Montserrat Volcano Observatory
My first two days here in Montserrat have been spent in talks with potential collaborators and sitting though presentations of research data. A volcanology conference is different from most scientific conferences. Here, there is mineralogy, geophysics and physical volcanology. But there are also talks about outreach to the public, the mechanics of ash shorting out transformers, and the effects of an active volcano on teenagers living their lives on the mountain.
Highlights so far: the mineralogy, of course. Hornblende chemistry is giving fantastic insights into the pressure relationships among the magmas: there are two storage levels. The combination of experiment and microanalysis makes it possible to look at textures that develop in igneous rocks during the eruption process. Then there is the volcano itself, and other volcanoes like it.
Much of the talk here is about pyroclastic flows (PFs) or pyroclastic density currents (PDCs) — the mixture of hot gas, rock and ash that erupts from a volcano. There is a more sinister component, called the surge. Sometimes a more gas-rich, very hot portion of the flow will separate out from the rest, and the surge, or base surge, will race ahead. Then there are block and ash flows, where the blocks are the size of small cars, and lahars, the deadly mixture of ash and water that floods settlements on the sides of rivers downstream from the volcano. In one talk, we learned that structures built to contain lahars at Marapi volcano may have actually contributed to the separation of a surge from the rest of the pyroclastic flow. The surge did the most damage.
It all comes down to topography and that is very apparent at Montserrat. I started to rent a bicycle for the week of the conference, but I recognized some switchback roads on the map, and realized this meant steep climbs. This move saved me from serious cramps in my calf muscles. Everything here is either uphill or downhill, and few flat places exist. The island’s rugged topography is divided into ridges and ghauts (pronounced “guts”). The ghauts and river valleys channel the PFs, the PDCs and the lahars.
I’ll leave you with one picture from today’s boat tour of the devastated town of Plymouth. It shows a blue cloud of sulfur dioxide gas that drifted down from the Soufriere Hills volcano. The cloud smells clean, sharp, and not unpleasant. But sulfurous gases combine with water to form sulfuric acid, which is why my lungs, nose and contact lenses burned a bit.