30th anniversary of Mt. St. Helens eruption: May 18, 2010

Ash cloud of the 1980 Mt St Helens eruption

A closeup of the 1980 Mt. St. Helens eruption. Image from Wikimedia Commons.

On May 18, 1980, Mt. St. Helens, a volcano in southwest Washington State erupted. The eruption caused billions of dollars in damage, and 57 people were killed.  While it was not the worst volcanic eruption on record, it still was a shock.  It took more than a few installment loans to clean up, and Mt. St. Helens has been closely watched since.

Mt. St. Helens 1980 eruption

Mt. St. Helens had been dormant for more than a century, but in March 1980, earthquakes began to shake the mountain. For the next two months, the mountain was closely monitored.  On May 18, an earthquake with a magnitude of 5 on the Richter scale shook the mountain. It triggered a landslide on the North face, which provided an outlet for the intense heat and pressure inside the volcano.  A blast of super hot gas, magma, and rock ripped out of the side of the mountain.

The blast

The pyroclastic (volcanic) blast that ripped through the side of the mountain as a result of the landslide reached the speed of sound.  Materials ejected by the blast spread over 20 miles. Pyroclastic flows (material pouring out of the mountain) continued after the eruption, and 17 were observed afterward. Two weeks after the eruption, the materials spewed forth from the mountain were still almost 800 degrees Fahrenheit.

The damage

The flow of debris and material extended almost 20 miles away from the mountain. Mud flows and debris were shot into river systems, causing floods and heavy damage to river systems. More than one cubic mile of debris was shot out of the mountain.  A total of 57 people died; 200 homes, 27 bridges, 15 miles of railroad track and 185 miles of highway were destroyed.  President Jimmy Carter flew out to observe the damage and compared it to the surface of the moon.

Further fallout

An ash cloud was shot 12 miles into the atmosphere.  Washington state was blanketed by ash fall, and by May 19, ash had covered Yakima.  Spokane, Wash., was plunged into total darkness, with a visibility of about 10 feet.  Ash fell as far away as Minnesota and New Mexico.  Airports were forced to ground flights as a result, like the recent Iceland volcano did.  The eruption released almost 1,600 times the heat energy released by the Hiroshima blast. The mountain was more than 1,000 feet shorter and left a crater almost 2.5 miles wide. Smaller eruptions and occasional activity still occur. Mt. St. Helens caused more than $1 billion in damages (almost $3 billion today).  It was among the worst natural disasters in U.S. history, and one more reminder that Mother Nature can be a cruel mistress.

Other recent posts by bryanh