Mayon volcano's ash is the biggest threat
January 26, 2018
DW: What kind of volcano is the Mayon?
Ben Andrews: The Mayon volcano is a stratovolcano in the Philippines. That's a volcano where most of the activity is focused in a very narrow spot or small area, so over time it builds up a nice, tall, often symmetrical cone of material. The term stratovolcano gives you a definition of what it is: strata would be layers, so a stratovolcano is made up of a whole bunch of different layers, stacked on top of each other, to build a very tall cone.
A volcano like Mayon is built through a combination of lava flows and lava domes, as well as explosive eruptions. And those tend to build up something that makes a steep-sided structure. The average slopes of Mayon are about 35 to 40 degrees. That's very different from volcanoes on Hawaii – those are shield volcanoes that build up through lots of lava flows that form a much, much gentler slope.
How often has this volcano erupted?
The eruptive history for Mayon volcano shows that there have been 66 eruptions that we recognized in the last 10,000 years. There are a lot of eruptions back to about 1800 and then one the 1700s, one in the 1600s and just two that were before that. That doesn't mean it didn't erupt prior to 1600, it just means the eruptions haven't been recognized. So if we phrase it another way, there's been about 63 or 64 that have been recognized at this volcano in the last 200 years. That's a lot. Mayon is a very active volcano.
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What would you say are the most dangerous factors about the Mayon eruptions?
Lava is a fluid almost like toothpaste or like pudding – it can flow but it doesn't flow very well. But then it hits such a steep slope that the lava breaks up and falls down the slopes. It looks like ash falling down the sides of the volcano. Those clouds of ash are called pyroclastic flows and they are one of the big hazards in an eruption like this.
You can think of pyroclastic flows as a super-heated, sand-blasting cloud. They might be 100 meters thick, they're moving at 30 or 50 meters per second and they're 500 degrees Celsius hot. They're bad news. They can destroy almost everything in their path.
Fortunately most of the pyroclastic flows in the latest eruption don't look like they're going beyond the slopes of the volcano. But the ash from Mayon's eruptions rises up into the air and if it gets in an airplane engine, the ash can destroy the engine.
It's also something you don't want to breathe in. If it lands on your house that can pose a problem as well, because volcanic ash is not like fireplace ash. It's powdered rock, which means it can cause your roof to collapse. That's the big thing: there's a lot of ash generated in these eruptions and that can pose threats even way beyond the local area of the volcano.
Geologist Ben Andrews is the director of the Global Volcanism Program at the Smithsonian Institution in Washington D.C.