Deadly river of lava, ash and rocks
Guatemala’s Volcan de Fuego (Volcano of Fire) erupted spectacularly Sunday, shooting a plume of ash and gas 6 km into the sky and spreading ash and debris across towns and farms more than 16 km away from the volcano.
A river of lava, rocks and ash poured down the mountain, burying homes and people. This river, or pyroclastic flow, may not be glowing orange like molten earth, but it is undeniably the most deadly part of the volcano. Do you recall that scene in
Independence Day , the one where the aliens detonate their weapon of mass destruction over New York City, Washington and Los Angeles?
A wall of fire tears through the cities, incinerating everything in its path. Jasmine, played by Vivica A. Fox, leaps into a tunnel service closet with her son and dog Boomer, narrowly escaping the fiery wave. It was a close call, but Boomer does not end up on the very bad list at doesthedogdie.com, and Jasmine and her son are safe.
Pyroclastic flow is kind of like the alien wall of fire in
Independence Day. It’s full of rocks, ash and hot gas. It blasts across the ground at speeds over 80 km/h and is incredibly hot — sometimes over 540C.
“It is universally deadly,” the U.S. Geological Survey (USGS) says.
There’s no service closet in the world that could save you when pyroclastic flow is shooting down the mountain.
Pyroclastic flow is how 30,000 people died in the eruption of Mount Pelee in 1902. When Vesuvius erupted in 79 A.D., more than 13,000 people died in pyroclastic flow, although the exact death toll is unknown. And it’s also being blamed for dozens of deaths in the Fuego eruption on Sunday.
“Hundreds of police officers, soldiers and emergency workers have been sent to affected areas on the slopes of the volcano,” the BBC reports. “They found charred bodies resting on steaming remnants of pyroclastic flow.”
There are several ways pyroclastic flow can develop during an eruption.
The plume of ash and gas above the volcano cools and falls to the ground. Amplified by gravity, the flow pulls hot debris down with it.
Instead of erupting into a big plume, the volcano can “boil over” and its contents flow rapidly down the mountain.
Like an avalanche, lava that piles up can become unstable, break off and shoot down the mountain.
Even though the pyroclastic flow just looks like ash, it’s actually a flash flood of rocks and boulders. Just like a flash flood, it will naturally flow into dips and valleys, but if the valley narrows or the volume of flow becomes too large, it will flood the surrounding area.