Article

15 October 2004

Earthquakes and volcanoes

Forrest M. Mims III

A fern emerges from an old lava flow on the slopes of Hawaii's Mauna Loa volcano, the world's most massive mountain. Photograph by Forrest M. Mims III. Click image to enlarge.

Mount St. Helens in the news again. In 1980, the volcano erupted in a massive sideways explosion that killed 56 people and dumped ash hundreds of miles away.

The 1980 eruption blew away the top 400 meters (around 1,300 feet) of the mountain. For the next six years, a giant lava dome was gradually built inside the volcano's crater. It reached a height of 300 meters (around 1,000 feet).

Recently Mount St. Helens roared back to life with a steam eruption that sent ash some 4,900 meters (around 16,000 feet) into the sky and forced airlines to cancel flights. As this is written, geologists are warning of a much bigger eruption to come. While it may not be as big as the 1980 blast, the U.S. Geological Survey warned people to stay away from the area. Some 2,500 people were evacuated from a visitor's center five miles from the mountain.

Scientists were able to predict the latest activity at Mount St. Helens by monitoring earthquakes at and around the volcano. The quakes are caused as molten magma rises from deep in the earth prior to an eruption. Earthquake activity at Mount St. Helens increased dramatically last week. Geologists measured hundreds of quakes.

Other major volcanoes around the world are also monitored for earthquake activity. Mauna Loa on the Big Island of Hawaii is the most massive mountain on Earth. Scientists have placed monitoring devices around key parts of this enormous volcano. One of those monitors is at the Mauna Loa Observatory (MLO), 3,400 meters (around 11,100 feet) above the palm trees that line much of the the coast of Hawaii. In fact I just took a picture of it.

A group of Forrest Mims's science students from the University of the Nations in Hawaii emerge from an ancient lava tube on the slopes of Mauna Loa volcano. Click image to enlarge.

Thanks to an annual teaching assignment at the University of the Nations, at least once a year since 1992 I have visited MLO to calibrate instruments that measure the ozone layer, the column amount of water vapor through the atmosphere, solar ultraviolet, the atmosphere's aerosol optical depth and other air quality parameters. Every two days I drive down to the coast for groceries, a swim and a shower.

Mauna Loa last erupted in 1984, when it sent a river of lava to the outskirts of Hilo. The mountain is overdue for an eruption. One may be on the way, for more than 580 earthquakes have occurred on the mountain since July. Two years ago, earthquakes twice shoved my feet against the wall while I slept here. This time the only booms are from bombs dropped by jets during military exercises down below.

Forrest M. Mims III and his science are featured online at http://www.forrestmims.org/.

This feature was originally published in Forrest Mims's weekly science column in the Seguin Gazette-Enterprise, Seguin, Texas. The column is written for a general audience.