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Cascade Range Weekly Update
Thursday, April 20, 2017 3:35 PM US/Pacific
Current Volcano Alert Level: NORMAL
Current Aviation Color Code: GREEN
Cascades Volcano Observatory's mission
The U.S. Geological Survey's Cascades Volcano Observatory strives to serve the national interest by helping people to live knowledgeably and safely with volcanoes in WA, OR, and ID.

HOT STUFF   (archive)
Young Volcanoes in WA, OR & ID1

Registration is open for summer teacher workshop at Mount Rainier.
March 09, 2017

Mount Rainier National Park is a unique classroom, rich in resources for observing geologic change. Join us July 17–21, 2017, for a 5-day educator workshop in the Park, where we will explore the diverse and dynamic processes that have shaped the volcano and share new classroom ideas that will engage middle school students. There is no charge for this workshop and camping is available to participants. Registration information is at the Mount Rainier Teacher Professional Development webpage.

Small magnitude earthquake swarms detected beneath Mount St. Helens.
December 12, 2016

Four swarms of small magnitude earthquakes were detected beneath Mount St. Helens beginning November 21, 2016. No anomalous gases or increases in ground inflation have been detected and there are no signs of an imminent eruption.

During a week's time, there have been over 120 tiny earthquakes, most too small to be formally located by the Pacific Northwest Seismic Network. The earthquakes are magnitudes 0.3 or less; the largest has been a magnitude 0.5. Most of the earthquakes are occurring in the shallow volcano plumbing system about 1-2 miles below sea level. These earthquakes are too small to be felt at the surface.

The current pattern of seismicity is similar to swarms most recently seen at Mount St. Helens in March-May 2016, and in 2014 and 2013. The magmatic system is likely imparting its own stresses on the crust around and above it, as the system slowly recharges. The stresses drive fluids through cracks, producing the small quakes. Subtle evidence of recharge has been observed since 2008 and can continue for many years. It is a sign that Mount St. Helens remains an active volcano.

For more information, see the Activity Updates for Volcanoes in CVO Area of Responsibility and Earthquake Monitoring at Mount St. Helens.

Lidar allows researchers to identify over 200 landslides in the western Columbia Gorge.
November 04, 2016

The western Columbia Gorge has been long recognized as an area susceptible to landslides. Abundant rainfall, steep terrain, geologic structure and erosion by the Columbia River combine to create topography capable of ground movement. Yet dense forests have hampered efforts to accurately map old and currently active landslides and to fully understand the scope of this hazard.

A new study uses lidar to map and characterize known and previously unrecognized landslides in the western Columbia Gorge, Washington. Lidar is a remote-sensing technique that provides images of terrain from which vegetation and structures can be digitally "erased" to show the underlying bare ground. Formerly hidden by forest, lidar reveals telltale landslide indicators such as scarps, cracks and ridges, slope depressions, bulges and toes.

The imagery shows that landslides cover about two thirds of the 222 square km (86 square mi) map area. Two of the largest landslides in the map area—the Bonneville and Red Bluffs landslides, averaging about 75 m (250 ft) thick with runouts of 6-7 km (~4 mi)—failed catastrophically and slid rapidly to the river within the last 600 years; the Bonneville landslide temporarily dammed the Columbia River and formed the "Bridge of the Gods" known from Native American legends.

Research shows that these landslides have complex movement histories and have been active over thousands of years; some have moved recently or are currently moving. Another such landslide rapidly sliding into the Columbia River today could have a catastrophic impact on downstream communities and on the transportation and energy-distribution infrastructure of the Pacific Northwest.

The publication, Landslides in the western Columbia Gorge, Skamania County, Washington, is available online.

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