Our Window on Nature

Years ago we were hiking high on Mount Ranier in Washington State when we saw a plume rising from Mount St. Helens far in the distance. It had to be some time after 1980, because that is when the volcano become active once again. Our first thought was of another eruption. Training our binoculars on the volcano, we finally decided it must be dust from a rockfall inside the dome.

The original eruption in 1980 reduced the height of Mount St. Helens by 1,314 feet, removing 3.7 billion cubic yards of material. But now the volcano is growing again, and it is the upward pressure that is causing the present tremors.

The volcano became active most recently in September of 2004, and since that time there have been many small earthquakes, each with a magnitude of less than 2.0 on the Richter scale. Now there are multiple quakes each day. Scientists say they don’t think an eruption is likely at the present time, but no one can tell for sure. Locally the small quakes are being called drumbeats, and the cause of the minor shaking is part of an ongoing dispute.

One group thinks that a “plug” is being pushed up — then released, and that rock rubbing against rock is causing the quakes. Another argues that it is steam inside the volcano and they say

vibrations in a steam-filled horizontal fracture about 330 feet (100 meters) beneath the crater floor are causing the drumbeats. There’s plenty of water in the ground, and there’s plenty of heat.

When the weather warms up, you can actually visit Mount St. Helens, but in the meantime (or if you don’t want to get that close), here is a WebCam view of the volcano. Just don’t bother looking at night, since the view is live.

At one time we lived next to an earthquake fault. It ran through a golf course just over our back fence. Of course, we lived there for several years before learning of its existence. A big quake came long after we had moved away.

Some years later we found ourselves in a similar situation while staying in a campground in central California. We were talking to some college students working on a surveying project – tracking long-term movement of the San Andreas Fault. They told us the fault zone ran directly under where we had our motorhome parked. Oops….

Different parts of the country have different hazards, whether it is tornados, hurricanes, or earthquakes. And usually the ones you fear most are those that occur in someone else’s backyard. Those nearby are the ones you understand, and I suppose that leads to a kind of acceptance. Living in the West we have become accustomed to an occasional shaking.

But the West doesn’t have all the excitement. Although the four largest earthquakes in the last several hundred years all occurred in Alaska, number five was the New Madrid, Missouri, quake in 1811. It wasn’t the strongest, but it was felt over the widest area. For some reason, the geology in the eastern United States allows shock waves to spread over a greater distance.

A recent study by the Nevada Seismological Laboratory at the University of Nevada listed the various states in order of their average seismic activity. Not surprisingly the top contenders were Alaska, California, Nevada, and Hawaii.

Want to get away from earthquakes? They can occur anywhere, but the two states that seem to have the fewest are Florida and North Dakota. However I’ve heard some interesting stories about hurricanes and tornados.