Pyroclastic Flow on EARTH Magazine

Pyroclastic flows, not caldera collapse, caused Santorini tsunamis

Tue, 14 Mar 2017 18:56:33 -0400

The massive 1650 B.C. eruption of Santorini caused the volcano to collapse, producing a caldera. The volcano is now a series of islands. Credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team.

The 1650 B.C. eruption of the Greek island volcano Santorini, located in the Aegean Sea, triggered tsunamis that heavily damaged coastal towns and disrupted vital shipping and trade operations, events thought to be important factors in the demise of the ancient Minoan culture.

Slow-moving super-eruptions still travel great distances

Thu, 16 Jun 2016 10:06:26 -0400

Deposits of Peach Spring Tuff from a super-eruption 18.8 million years ago can be seen throughout Arizona, Nevada and Southern California. Credit: David Buesch.

When Hollywood movies depict the destruction unleashed by volcanic eruptions, they usually focus on red-hot lava, but even more dangerous are pyroclastic flows: mixtures of rocky debris and searing hot ash and gas that move as fast as 700 kilometers per hour and can bulldoze, incinerate and suffocate anything in their paths. In a new study looking at pyroclastic flow deposits associated with the Silver Creek Caldera in the southwestern U.S., researchers have found that not all pyroclastic flows are so swift. Dense, slow-moving flows can still wreak havoc over vast distances.

Hazardous Living: Thirty years after Mount St. Helens exploded

Thu, 05 Jan 2012 06:41:58 -0500

Megan Sever (pictured at Yellowstone) writes Hazardous Living for EARTH. Megan Sever

Thirty years ago today, sometime not long after 8:30 a.m. Pacific time, Mount St. Helens explosively erupted. The shock wave from the eruption washed over Oregon and Washington, shaking the ground up to 400 kilometers away. Two earthquakes followed, at 8:32 and 8:34 a.m. Shortly thereafter, with a tremendous burst, the upper north flank gave way as gas, steam and ash vented outward and sent out an immense landslide of hot rock, mud, water, ash and debris. It was the worst volcanic disaster the United States had seen.