EARTHQUAKES : TICK TOCK

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More Earthquakes Under Northwest Volcanoes,

Mt. Hood Shaken by Quake Swarm
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A FEW WEEKS back, we heard news of an small earthquake swarm underneath Mount St. Helens. Now, media-driven hyperbole aside, that swarm was business-as-usual for a Cascade volcano, where magma slowly rises back into the upper parts of the system. So, it should be no surprise when other volcanoes in the range show similar behavior. That’s what we might be seeing right now at St. Helens’ southern neighbor, Oregon’s Mt. Hood, where the USGS has noticed a swarm of small earthquakes (all less than M2) that started on Sunday.

It has been over 200 years since Hood’s last eruption, a period that is referred to as the “Old Maid” eruptive period when a small lava dome was formed just off the volcano’s summit. This activity produced some pyroclastic flows that swept down the southeastern sides of the volcano, along with some lahars (volcanic mudflows) that headed down some of the rivers that come off of Hood, like the Sandy River (see below). The Sandy got its name thanks to what may have been lahar deposits in its channel when Lewis and Clark came by a few years after the eruptions. A few small explosions likely occurred during the 1800s, but since about the 1860s, the volcano has been completely quiet.

As of 1 p.m. Monday, Oregon’s Mount Hood has seen about 40 earthquakes in close proximity over less than 18 hours. Such clusters of earthquakes are known as a swarm. The location of the quakes is on the southern flank of the volcano, and they are small, magnitude 2.0 or less. Alicia Hotovec-Ellis is a volcano seismologist at the Pacific Northwest Seismic Network at the University of Washington and an expert on earthquake swarms. She says the swarms have happened in the same place before. The quakes on Mount Hood are not seen as a warning of an eruption and are probably related to water moving through rock.

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POWEERFUL 6.7 MAGNITUDE

EARTHQUAKE HITS ECUADOR

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SUSPICIOUS OBSERVERS

INCREDIBLE NEWS

 

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HUNDREDS FEARED DEAD

MUDSLIDE IN SRI LANKA

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