The following story was published in the Nisqually Valley News. It tells the story of my experience with iMUSH.
I participated in a scientific endeavor called iMUSH in July and August of 2014. While this may sound like Apple has come out with a new type of breakfast cereal, iMUSH is an acronym for imaging magma under Mt. St. Helens. The goal of this project is to create a 3D image of the magma chamber that lies under the mountain. I will explain the details of this large undertaking later in this article, but first I want to talk about some of the people involved.
I am a Science teacher at Eatonville Middle School and have done geology field work at Mt. Rainier. I try to keep close tabs on work that is being done at Mt. Rainier so I heard about iMUSH. I contacted Alan Levander and Eric Kiser at Rice University and volunteered to work on the project. I was delighted to be put on the team. The iMUSH team was big and multi-national.
iMUSH is a collaboration among Rice University, the University of Washington, Columbia University, Oregon State University, ETH Zurich, the USGS, the US Forest Service, and the PNSN. There are lots of fingers in this pie. I arrived at the “Instrument Center” in Castle Rock, WA, and there I met the team. People were from everywhere. Two from Switzerland, four from Germany, a handful from Portland, five from Texas, and singletons from California, Oklahoma, Boston, New Mexico, Spain, etc. All of them had flown into Portland and then drove up in rented SUVs. They were all either undergraduate or graduate students in geology. I realized that I was the only local and non-student when we did our round of introductions.
After getting settled in, we started the process of training. Our job was to deploy and pick up seismometers. A seismometer is a device which records the shaking of the ground during an earthquake. We were deploying a type of seismometers called “Texans.” They are called Texans because they are commonly used in the business of oil exploration which is common in Texas. These small, portable, expensive Texans have a geophone attached to them and they run on batteries. Each geophone and Texan cost about $3,000. Texans can record earthquakes for about four days on their batteries. We were given boxes of Texans, a GPS device, a pickax, a personalized detailed map, a log book, and a rented SUV. We each had a partner and then headed out into the field.
Imagine the spokes on a bicycle wheel with the hub at the center of the spokes. The hub is the crater of Mt. St. Helens and the spokes are lines of deployed Texans. We were split up into partners and were given a spoke, or line, on which to deploy Texans. Charlene Batchelor, my teammate, and I considered ourselves lucky because, on our first deployment, we were on the main "X" line that went from basically the base of Mt. St. Helens outwards in a northwest direction. The views were stunning. We placed the Texans, using GPS coordinates, in a line moving away from the center. Each group of partners had their own spoke, or line, of seismometers that they were responsible for. On one day Charlene and I had 60 Texans in our SUV. At $3,000 a pop, we were carrying around $180,000 worth of equipment. The deployment of the Texans was simple. Once we reached the correct location, I wrapped the Texan in a garbage bag to protect it, dug a hole using a pickax, placed the geophone and Texan in the hole, covered the hole, and then marked and logged the site. We then moved to the next spot and repeated that procedure. We would have three days of deployments and two days of picking up after the “shots.”
So what are “shots?” Imagine the bicycle wheel again, with the hub being Mt. St. Helens, the spokes being seismometers. The tire itself, the circle at the end of the spokes, is roughly where the explosions, or shots, took place. The explosive team had placed and set up these explosives weeks before the deployment. So, why use explosives – couldn’t you just use naturally occurring earthquakes? Well, as you could probably guess, scientists have no control over the timing, the magnitude, or placement of natural earthquakes. Remember, the battery life for a Texan is about four days. After the teams deployed these lines of seismometers and before the batteries ran out of juice, the explosive team set off a series of explosions in a ring around Mt. St. Helens. I attended the first shot. It was at ten at night in a secluded area in the woods. All the shots were carefully picked so as to cause the least disturbance to people who lived nearby. It was pitch black, raining, and the explosives team worked using the lights of a pickup truck. They blew the warning trumpet, counted down, and then over 1,000 pounds of explosives detonated under our feet. Imagine standing on an elevated board and somebody hits the bottom of the board with a sledgehammer as hard as they can – that is what it felt like to stand there. While we stood around giggling, the explosive team raced off to their next site because they had seven more explosions to set off before dawn arrived. I was a little bummed to find out that I had attended the smallest explosion. Apparently at the bigger explosions, where 2,000 plus pounds of explosive were used, people got an inch or two of air under their feet. These shots generated artificial earthquakes that registered around two on the Richter scale. While comparatively small on the Richter scale, and basically unnoticeable by humans outside of the blast site, these shots are easily picked up by the sensitive Texans. After the shots were over, teams went out and collected their Texans. The Texans were brought back to the instrument center and all the information was downloaded into computers. New batteries were placed in the Texans, new maps were handed out, and we repeated the steps of deployment, shots, and the picking up of Texans. So what would these seismometers show us?
Texans record seismic waves. I want you to get an idea of what seismic waves are. Get a friend and have them slap objects while you, with your eyes closed, have your fingertips on the other end of those objects. For example, your friend slaps a table and you will feel and hear the vibrations from the slap. Now try a different object; notice that the sound and vibrations are different! The explosions, or earthquakes, are like the slap and they send out vibrations that can be sensed by the seismometers, which are like your fingertips. The explosions will send seismic waves through the Mt. St. Helens magma chamber and the waves will change as they go through different stages of rock or magma. This difference is the key. I will over-simplify here, but basically you can plot the point where it goes from rock to magma and vice versa. Create enough of these points, and you can create a 3D picture of the volcano's magma chamber. Cool, huh? In total, over 2500 Texans were deployed, recovered and their information was downloaded. Now Alan Levander and his team from Rice University will bring that info to a supercomputer, crunch this avalanche of data, and create a never before seen, fine-grained, detailed picture of Mt. St. Helens’ magma chamber.
On my last deployment, Charlene and I had the northernmost line and our final group of Texans was placed at the end of Bald Hills Road and on Weyerhaeuser land. It was cool and strange to be deploying in a familiar environment. (Thanks go out to Weyerhaeuser Corporation, the Department of Natural Resources, WashDOT, counties like Thurston and Chehalis, and a number of land owners near Mt St Helens who gave permission for team members to place Texans on their land). iMUSH is a huge collaborative effort that has taken years of planning and it is still going. More data is going to be gathered, but the huge lump of data gathered this summer will take more than a year to parse out. Expect to see the results of the study in 2016.