Posted by: magmatist | August 28, 2010

Research report: Melissa Park’s Sherman Crater ice radar project

South Crater rim seismometer retrieved; Sherman Crater radar report

Melissa Park with her GPR data recorder. Think she's having a good time? Click to enlarge any image.

Here is a first-person research update from Melissa Park, Western Washington University graduate student, Mount Baker lover (she has a tattoo to prove it!) and temporary Sherman Crater ‘owner’ (until she is done).  Melissa’s thesis project has been to map out the thickness and volume of the glacier in Sherman Crater, using a ground-penetrating radar. This can provide an assessment of the possible volume of melt water that could flow out of the crater if thermal levels increase, say prior to renewed eruptive active.        dt

Tyler Kent digs out CRIM Wednesday, August 25, 2010.

The first new snow of the season fell on Mount Baker yesterday (August 26, 2010). Five inches fell on the south rim, where just the day before Tyler Kent and I retrieved the crater rim seismometer (station CRIM). Lauren Hogan and I, with the help of a small team of assistants, buried this brave and patient seismometer in early August of 2009. A few attempts were made to retrieve it last year, but the unusual heat and dryness toward the end of last summer rendered the Easton Glacier route impassable. A few attempts were also made this year, but the south crater rim, usually snow free by late June, was still completely covered just a week ago. It was sheer luck that we were able to retrieve the unit in the very small window of opportunity the mountain allowed us. The unit will be returned to Dr. Jackie Caplan-Auerbach, WWU seismologist, for data analysis. The data it contains might shed light on the mysterious swarm of long period earthquakes that took place last year near the upper part of the Easton Glacier.

Installing CRIM the first time, in 2007. Melissa, with Ned Hannah and Jamie Yoos.

The mountain also saw the return of the Ground Penetrating Radar (GPR) twice this year. In early July, a small team of intrepid radar operators collected a set of data along one transect across Carmelo Crater. Then, in mid-July, my team and I spent two nights and a full day with the radar inside Sherman Crater. We were able to collect 4 transects of radar data and hundreds of GPS waypoints. I had hoped for more data, but the radar is a finicky beast that gobbles battery power to show its discontent when placed in cold environments. I will use the GPS waypoints to create a relief map of the crater’s glacier surface and the GPR data to map the bottom of the glacier. By combining calculations of glacier thickness, annual mass balance and surface melting, I can estimate the geothermal flux currently coming out of the crater. My preliminary estimate (~26 Wm-2 [watts/square meter]) is within the range I expected for Mt. Baker – more than the geothermal flux right before the 1975 event but well below the heat measured at craters holding volcanic lakes. I had also hoped to rappel into one of the fumarole holes this year (the Dragon Hole, a.k.a. the southwest pit) to measure the thickness of annual snow layers, but the hole never materialized. I suspect the mountain did this on purpose, but whether out of mockery or over-protectiveness I do not know. Some have questioned the soundness of such a venture, even after I equipped myself with a state-of-the-art gas analyzer to quench their concerns.

GPR team on traverse in Sherman Crater. Pooch Peak in background. Gas rises from SW pit fumarole.

I now have all the data I will collect for my Masters thesis. I will keep you updated as I uncover the secrets of the crater glacier. Based on the data gathered last year I think they will be plentiful. I was able to calculate that the crater glacier is ~50 meters deep with a surface velocity of ~3 to 4 m/month during the summer months. I discovered that the obvious east-west snow ridge running across the crater glacier is not the result of a subglacial topographic ridge, but of melting of ice on each side of the ridge (Dragon Hole to the south, Northwest Pit to the north) and I found a flat feature underneath the ice, in the approximate location of the 1975 crater lake, that might be a subglacial lake. Very exciting! I still have much data analysis ahead, all of which will take place in front of a computer, so pray for sad gloomy weather to lessen the draw of outdoors play.

View south to Sherman Crater from the summit of Mount Baker, 2004. The 'dragon hole' fumarole is the dark pit in the icefield. Melissa's 4 GPR transects traverse the glacier.

I would like to thank members of my 2010 fieldwork teams for their hard work and enthusiasm:
Carmelo Crater GPR team: Dacia Grayber, Keith Kemplin, Doug McKeever and Topher ?.
Sherman Crater GPR team: Neil Bush, Evan Larsell, Mike Ruark, Austin ?, Doug McKeever and Braden Zwade.
Seismometer retrieval: Tyler Kent.


Responses

  1. good to see you were serious about a degree in geology, Melissa! looks like wonderful work!

    Barbe Park


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