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Scientists: Mt. Hood Hit By 6.7 Quake In 9,600 B.C.

Scientists say they have new information on the history of Mt. Hood earthquakes. The last big quake on Mt. Hood occurred about 11,700 years ago, according to preliminary data collected by the Oregon Department of Geology and Mineral Industries.  

Mt. Hood shakes a lot. There was a swarm of small quakes just last month. But they were only magnitude one or two, so nobody felt them. Now, state scientist Ian Madin says there’s evidence the mountain can quake violently. By digging down into a newly-discovered fault, and radio-carbon dating organic vegetation buried after the last big quake, Madin has found Mt. Hood was hit by a 6.7 quake in about 9,600 B.C.

Madin said, “We estimate the magnitude, and estimate is important, by looking at the amount of movement on the fault. There are two ways you can do this. How long was the fault when it broke? And how much did it actually move?”

Madin says that nearby towns, like Government Camp and Parkdale would have felt the quake, if they had existed at the time. But the quake probably wouldn’t have knocked down all the homes. Madin says Mt Hood is an ‘active’ volcano — Lewis and Clark missed its last eruption. The mountain’s faults were found by a new kind of mapping equipment, called Lidar.

On the Web

Pacific Northwest Seismic Network

Oregon Dept. of Geology