Mt. St. Helens 5/18/80May 18th, 2013 at 1:49 am by Bill Steffen under Bill's Blog, News, Weather
Today (May 18) is the 33rd anniversary of the biggest (and there were a handful) explosion of Mt. St. Helens, the last big volcano in the Lower 48 states. The picture on the left is the mountain before the explosion (center). The image on the right is damage to trees. The explosion that occurred on May 18th, 1980 at 8:32 AM local time destroyed 4 BILLION board feet of timber, enough to build 300,000 homes. The initial blast-thrust was 300 mph. According to the USGS, the landslide caused by the collapse of the northern slope of Mount Saint Helens was the largest debris avalanche on Earth in recorded history. Within 15 minutes ash was blown into the stratosphere to a height of 80,000 feet. The ash cloud passed over Grand Rapids two days later (I have a slide I took of the ash cloud, which looked like a thick, uniform cirrus cloud layer) and circled the globe in 15 days. Ash accumulation was 10″ deep ten miles from the volcano and 1″ deep sixty miles from the volcano.The height of the mountain was reduced by 1,314 feet. The blast began with a 5.1 magnitude earthquake. Fifty-seven people were killed that day, 250 homes, 47 bridges, 15 miles of railway and 185 miles of roads were destroyed. Here’s more facts – more pictures, a link to the National Monument website, and the Wikipedia article.
Volcanoes have become quite active in the last few weeks. A number of volcanoes are erupting right now, including the Pavlof volcano in Alaska. The plume from Pavlof rose to approximately 20,000 above sea level and have created a diffuse plume trailing 100 miles downwind. Popocatepetl in Mexico has erupted. Ash fell in three villages. Government officials have raised the threat level from one to three (third highest rank). Four people were killed as Mt. Mayon in the Philippines erupted without warning on May 7th. Shiveluch in far east Russia produced an ash cloud that rose 15,000 fee. The Stromboli volcano remains active in Italy. Observers spotted a small flow of lava from the volcano’s northeast crater. We still have the more prominent erupting volcanoes like Mt. Etna in Italy and Kilauea in Hawaii.