Earthquake Lakes

The international headlines are full of the "quake lake" story—in Sichuan, China, the earthquake-ravaged regions are threatened by accumulations of water trapped behind landslides acting as dams. The same thing happened in Pakistan in 2005. It happens every time a major earthquake strikes in mountain country. So it wasn't news to geologists, but today it's news to everyone. If your geology textbook doesn't mention landslide damming, expect the next edition to do so.

Landslide dams are dangerous because landslides don't make good dams. As soon as the water rises enough and starts to spill over, it can quickly cut a channel right through the rubble and start a nasty flood as the lake drains. That's why the Chinese are cutting channels proactively, and the disaster-response community will be watching this effort closely. I can only hope that the Chinese experts will report their experience so the rest of us can learn from them.

Geologic hazards have a life cycle in the public awareness. For more than 30 years, Americans didn't think about tsunamis very much (except in Hawaii where the memories of tsunamis in 1960 and 1947 stayed fresh). Then came the Sumatra tsunami, which killed vacationers from everywhere in the world, and now the word is back in the common vocabulary. America has its own "quake lake"; in fact it's still there in Montana, named Earthquake Lake. The Army Corps of Engineers cut a channel to help it drain. The landslide that blocked the Madison River and created Earthquake Lake happened during the Hebgen Lake earthquake of 17 August 1959, in the Yellowstone country. That's almost 50 years gone now, and only the locals remember. But if you're driving through on a Yellowstone vacation, take a moment to visit the visitor center along the Madison River.