Today in weather history: Eruption of Mt. St. Helens

Photo Courtesy USGS
Photo Courtesy USGS

CHARLOTTE, NC (WBTV) – On this date in 1980, Mt. St. Helens violently erupted in Washington state, sending millions of tons of ash into the atmosphere.

The area had seen approximately 10,000 smaller earthquakes around the volcano before the eruption, and the USGS had been monitoring it for months before the eruption on May 18.  Even though there had been warnings, fifty people were killed.

The eruption was so violent, that a large part of the mountain slid away, creating the largest landslide in Earth's documented history.

An 80,000 foot high cloud of ash developed and began to spread.  A complete blackout was reported in Spokane, nearly 250 miles away.  Ash was deposited in eleven states, and after three days ash had traveled to the East coast.  In just over two weeks, it had circled the Earth.

Prior to the eruption, Mt. St. Helens was 9677 feet tall. Afterwards, Mt. St. Helens was only 8363 feet tall, a change of 1314 feet.

Multiple lightning strikes were recorded as plumes of ash were forced higher into the atmosphere.  While the exact cause of these strikes is still debated among scientists, most generally agree that particles traveling at such high rates of speed can break apart or collide with one another.

Some form of aerodynamics causes the negatively charged particles to be separated from the positively charged, just as we would see in a thunderstorm.  Lightning will occur when the charge separation is too great for air to resist the flow of electricity.

While spectacular, this is a fairly regular occurrence for this volcano.  Mt. St. Helens has erupted nearly every one hundred years since 1400 A.D.