Friday Headlines, March 21, 2014
THE LATEST IN THE GEOSCIENCES
Massive landslide in Washington takes out a whole community
50 years after Alaska’s greatest earthquake
This week’s top headline is a massive mudslide that occurred in Washington state on Saturday, March 22 at about 11 am local time.
Buried under as much as 20 feet of concrete-hard mud are about 49 buildings, any of which may have been occupied.
A 1500 foot wide, 600 foot tall scarp was left behind.
Mudslides are a very real danger throughout the world.
When they occur, a large scarp is left at the top, while a fast-flowing toe moves forward and buries whatever lies in its path.
A large crack in the Earth’s surface is often evident where the scarp will later be much prior to a landslide event. If you see a large crack or fissure in a slope above where homes are, be aware that a landslide is possible.
Here’s a photo of a much smaller landslide (slump) that I saw in the mountains of Utah a few years ago.
Slumps and landslides can happen anywhere, but tend to be most common in regions with heavy rainfall and steep slopes, such as the western coast of the United States.
Follow this link to see a video that illustrates why you can’t just escape from a mudslide. No, this is not the Washington slide. This one took place on Kootenay Lake in BC Canada a couple of years ago.
50 years ago, on March 27, 1964, a magnitude 9.2 earthquake shook Alaska near the city of Anchorage. The shaking lasted over four minutes.
Earthquakes along the southern boundary of Alaska and the Aleutian Island chain are not surprizing, as this is a major subduction zone. The Pacific Plate (which forms much of the floor of the Pacific Ocean) is slipping underneath the North American Plate, upon which resides the state of Alaska.
You can read a bit more about earthquakes and plate boundaries here.