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Mount St. Helens sees increased seismic activity as anniversary of eruption nears

Mt. St. Helens

Plume of gases from Mount St. Helens viewed from Harry’s Ridge by the U.S. Geographical Survey. Public domain.

This year, May 18th will mark the 36th anniversary of the eruption of Mount St. Helens, an active stratovolcano situated in Washington State’s Skamania County and part of the Cascade Range of mountains. The volcano sits less than 100 miles south of Seattle, WA, and 50 miles northeast of Portland, OR, and it’s only one of 160 active volcanoes found in the Cascade Volcanic Arc. In 1980, an earthquake measuring 5.1 on the Richter scale caused an explosive event which saw the decimation of 150 square miles of forest caused by a lateral burst of mud and rock. The eruption also killed 57 people, nearly 7,000 big game animals, about 12 million fish in local hatcheries and dealt extensive damage to 200 homes.

The upcoming anniversary looks like it’s shaping up to be a special one for this major volcano, which is no longer dormant. With that in mind, we take this opportunity to return to our Disaster Tech series, this time with an eye toward research and development of technologies relating to volcanic activity. 

A recent weekly update on seismic activity measured at the Cascades Volcano Observatory (CVO), produced by the U.S. Geological Survey (USGS), reports a “continued pattern of slightly elevated seismicity” at Mount St. Helens. This seismic activity has been going on for about two months. More than 130 earthquakes ranging in depth from 1.2 miles to 4 miles have been detected in the region since March 13th by the Pacific Northwest Seismic Network (PNSN). Most of the earthquakes measure a magnitude of 0.5 or less but their frequency has been stunning, with as many as 40 earthquakes per week, which has led scientists to believe that the volcano may be recharging even if it won’t erupt any day soon.

The PNSN involves a series of more than 300 seismograph stations spread throughout the Pacific Northwest operated collectively by the University of Washington and the University of Oregon. Research is sponsored by the USGS as well as the U.S. Department of Energy (DoE) and the state governments of Washington and Oregon. This network, the second largest of its kind in the United States, began in 1969 with five operating seismograph stations. Early techniques employed by PNSN included recording seismometer readings on 16 millimeter (mm) film. Those films would be chemically processed and analyzed with a computer to determine the quake’s epicenter in about an hour.


Over the past decade, measuring changes in the surface elevation of Mount St. Helens crater has been made much more accurate with the use of light detection and ranging (LIDAR). LIDAR is an airborne imaging technique and it has been used to track ground deformations at Mount St. Helens since the rate of deforming began to pick up back in September of 2004. As of that time, the LIDAR technologies employed were capable of detecting a new uplift in the Mount St. Helens crater measuring 360 feet in height and 130,000 square meters in area. To conduct the survey with LIDAR, aircraft carrying scanning laser rangefinders to measure the distance between the aircraft and the ground surface thousands of times every second to an accuracy within four inches. Collecting data on these types of deformations allow scientists to track volcanic activity such as the movement of gases or magma under the surface. Researchers from the USGS have been aided by NASA scientists for previous LIDAR laser mapping projects.

Increased volcanic gas output of a volcano can be an indicator of growing volcanic activity as new magma rushes in and gases are forced out. At Mount St. Helens, volcanic gases like water vapor, carbon dioxide and sulfur dioxide are measured through a variety of techniques. On-the-ground monitoring methods include direct measurements at fumaroles, or vents in the ground which emit volcanic gases, as well as chemical analysis of nearby water sources to assess the level of gas content the water contains. The first major survey of volcanic gases at Mount St. Helens took place in the eight years following the 1980 blast although airborne surveys were renewed between 2004 and 2008 in response to increased seismic activity at that time.

That increase in volcanic activity beginning in 2004 put the USGS on notice as to a number of flaws in the agency’s monitoring programs as crucial seismic monitoring equipment were destroyed in early eruptions. In response, the USGS deployed monitoring equipment on lightweight frameworks which came to be known as spiders. Each spider housing consisted of an aluminum case containing batteries and a weatherproof plastic case holding the electronic components which measured earthquakes, lava dome extrusions, volcanic gas emissions and more. These units weigh little more than 150 pounds and cost between $2,500 and $7,500 per unit to produce.

Early warning systems for seismic activity are poor, at least with respect to providing ample notice for even major events, but scientific discoveries coming out of the University of Glasgow shows signs of promise. The Glasgow discovery may enable miniature gravimeters, which can be produced at a miniature scale for much less money than conventional units. The Wee-g compact gravimeter prototype developed by researchers utilizes micro-electromechanical systems (MEMS) similar to those used in smartphone accelerometers. The Wee-g’s 10-mm-square sensor reads changes in the Earth’s gravitational field picked up by a silicon string which is ten times thinner than human hair. Installed in networks around active volcanoes, this type of gravimeter could be used to inform early warning systems by obtaining detailed measurements of magma intrusions.

With all of the focus on Mount St. Helens over the past few decades, it bears mentioning that this particular volcano is not the most active one found in the Cascade Range over the past few thousand years. In terms of lava flow, the most productive area of the Cascades is the Santiam Pass and McKenzie Pass regions found in the central part of the mountain range. It has produced more than 3.5 cubic miles of lava over the course of its highest period of volcanic activity spread out over the past 5,000 years. Scientists have noted that the majority of the volcanoes found in the Santiam and McKenzie regions are monogenetic, meaning that the volcanoes will more than likely remain inactive after their main active period. As a stratovolcano, Mount St. Helens is polygenetic and will very likely see another major explosion in the future.

There’s very little to protect the human body from the intense heat of lava flows or the incredible brute force of a rockslide caused by an eruption. Researchers in Iceland, however, are trying to see if volcanic activity can be used, if not exactly harnessed, to provide geothermal sources for the generation of electricity. Failed searches for superheated underground water reservoirs in the past have led to discussions over whether molten rock trapped within volcanic bedrock could be utilized as a source of renewable energy. Further research on the topic is conducted by the Iceland Deep Drilling Project, an initiative led by a consortium of three Icelandic energy generation companies which is looking into the economic feasibility of extracting energy and chemicals from hydrothermal systems at supercritical conditions. When early drilling hit molten rock instead of the intended underground reservoirs it was seen as a failure, but researchers soon discovered that they could create a magma-enhanced geothermal system using natural rainwater reservoirs in conjunction with a transport system that directs heated water towards the Earth’s surface. Flow tests conducted in 2010 produced up to 20 megawatts (MW) of power.


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2 comments so far.

  • [Avatar for John]
    May 17, 2016 11:31 pm

    There are also reports of increased earthquake activity at Mt. Hood and Rainier right now. Pretty much like St. Helens it seems but is interesting that 3 are in a line more or less with each other. Always appreciate articles like this. Here in Washington, this is volcano awareness month so perhaps the timing is with good reason. Time will tell but it is good that people are made aware of these things and written so as to raise the awareness and not have people in a panic. Just makes sense to have good plans.

  • [Avatar for Steve Brachmann]
    Steve Brachmann
    May 19, 2016 12:39 am

    @John – There’s a really useful visualization tool available on the Pacific Northwest Seismic Network’s official website, there’s a link to it in the third paragraph of this piece. It’s pretty striking to see the frequency of Mount St. Helens versus other volcanoes in the region, although Mt. Hood’s recent uptick in activity is reflected as well.