The Power Of Volcanic Ash

June 9, 2018

What is it about an erupting volcano that is so destructive? Is it the speed at which rocks and lava project from the volcano? Or does the real danger come after the eruption?

Fuego volcanic eruption in 2013 on a moonlit night. By Kevin Sebold, photographer – Own work, CC BY 3.0,

Perhaps it’s both. When the Fuego volcano in Guatemala erupted this week, it wasn’t big news at first. In fact, the areas surrounding the volcanic mountain are used to small volcanic eruptions. But this time was different. Fuego is a stratovolcano, which means it builds up over time with alternating layers of lava and ash. When it erupts, the rock is broken down into small pieces of ash that can mix with gases to create a dust cloud. In this case, the cloud rose up ten kilometers and was noted by NASA satellites from space.

The most dangerous part of this type of volcano is the flow, called a pyroclastic flow, which consists of hot lava blocks, ash, and gas. The temperature of this flow—sometimes as high as 1,000 degrees Fahrenheit—is also extremely swift, flowing down mountain tops at speeds of up to 400 miles per hour. Think you can outrun this lava flow? Likely not.

The Fuego eruption devastated surrounding villages, killing more than seventy people and drowning homes and buildings in ash. Weather experts are watching out for something else as well: rain! When heavy rains flow, the mudslides of ash can cause even further damage.


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