lowly rising under the mountain since early March. The sudden release of steam from the top of the magma chamber resulted in a lateral blast that traveled to the north at 600 mph, knocking down and covering over 235 square miles of forest area. Following lateral blast, the volcano released a vertical eruption column that continued for the next nine hours, reaching an eruption height of 16 miles and discharging about 35,000 cubic feet of volcanic ash.

One of my college classmates, David Johnston, was about 6 miles north of the volcano at a U.S. Geological Survey observation post. He was never found. He and 63 other people were killed by the eruption. Total damage was in excess of $3 billion. The total energy release from this eruption, including the earthquakes, the steam explosions, the landslide, the lateral blast and the eruption column, totaled about 5 trillion kilowatt hours. This is such a large number, 5 followed by 12 zeros, that it is hard to understand. During the nine-hour eruption, the volcano was producing 250 times more energy than the entire U.S. power generation capacity; it was enough energy to make 100,000 cups of coffee for every man, woman, and child in the U.S. We were lucky; this was a small eruption.

Krakatoa volcano in Indonesia erupted in 1883 and produced an eruption 20 times bigger than the 1980 Mt. St. Helen's eruption. This event produced a massive tsunami that killed 36,000 people and the explosion was heard over 2,900 miles away, but it still isn't the biggest event. In 1815, the Tambora volcano in Indonesia produced an eruption more than 100 times bigger than the 1980 Mt. St. Helen's eruption. The exact death toll is unknown. More than 10,000 were killed directly, and as many as 80,000 may have died afterwards from poor sanitation and starvation. Closer to home, the Katmai, Alaska, eruption in 1912 was 30 times bigger than the 1980 Mt. St. Helen's eruption and the Mount Mazama, Oregon, eruption in 4600 BC was 50 times bigger.

The Katmai eruption produced the "Valley of 10,000 Smokes" when the hot volcanic ash filled a nearby valley and continued to release steam for the next 20 years. The Mount Mazama eruption covered 5,000 square miles with more than 6 inches of volcanic ash, and formed a "Crater Lake" 5 miles wide and 2,000 feet deep. Fortunately, these events occurred in areas that were sparsely populated.

The name "super-volcano" is reserved for the volcanic complexes that produce really big eruptions. In Long Valley, Calif., is a large collapsed structure called a caldera that was produced by a series of eruptions 770,000 years ago that were about 600 times bigger than the 1980 Mt. St. Helen's eruption. The Yellowstone caldera had an eruption 640,000 years ago that was 1,000 times bigger than the 1980 eruption, and an eruption 2.5 million years ago that was 2,500 times bigger. The La Garita Caldera in Colorado is 22 miles wide by 47 miles long and was produced by an eruption 28 million years ago that may have been 5,000 times bigger than the 1980 eruption.

These calderas form depressions that you could easily drive across without realizing that they were, in fact, volcanoes. The size of their eruptions mark these volcanic centers as super-volcanoes.

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