Nature Notes

Ashford, Washington

Vol. II September-October, 1985 No. 7

Nature Notes is issued bimonthly by the Naturalist Staff of Mount Rainier National Park. Material contained herein may be used freely in any manner, provided credit is given to this pamphlet and the author.
William Dengler
Chief Naturalist
Neal G. Guse

A DAY AT THE DOME - A Mount St. Helens Field Trip

It was a scene out of the most classic adventure movie. The sun baked the dry, seemingly desert-like terrain. The line of people trudged continuously onward and upward. Their destination: a black, smoking dome of rock. Scenes from Raiders of the Lost Ark kept flashing through my brain. Harrison Ford must be crouched behind the next boulder, ready to spring into action, and surely this must be the third sequence in the Raiders series!

Actually, it was August 22, 1985 and as unreal as the scene appeared, it was truly happening, well, at least in a way. The setting was Mount St. Helens restricted zone. The line of people included geologists from the Cascade Volcano Observatory (CVO), and a limited number of naturalists from Mount St. Helens National Volcanic Monument and Mount Rainier National Park. Their destination: the black smoking DOME!

The night before the trip I had a hard time sleeping. I well knew how lucky I was to be allowed the privilege of going into the crater itself. Up until now, only scientists from the United States Geological Survey (USGS), and University of Washington and reporters had been allowed access, and the reporters helicoptered in! We were destined to walk, nine miles and climb 2800', but it only added to the excitement. Now that the adventure is over and I have assured myself I really did go, I can sit down and share what I experienced with hers!

The first big excitement was getting my own respirator. Not that we did actually ever use the respirators, but that it is standard volcanology gear, to protect against breathing noxious gases. Off we went!

Norm McLeod, scientist in charge at CVO, and Harry Glicken, avalanche-debris whiz from U.C. Santa Barbara took turns making stops along the way into the crater. The additional task of route finding was also placed upon Norm. Rapid erosion of the slopes at St. Helens, made route finding a challenge, but Norm had boundless energy and trotted ever ahead. His leadership was in the true interpretive fashion. He was always including safety messages and chastised us often for not taking photos of ourselves in the crater. "Years from now, it's yourself you'll want to see!"

The stops along the way, introduced us to the various volcanic deposits: pyroclastic flows and surges, debris-avalanche deposits, basaltic lava flows and pumice falls. I felt the men were to be congratulated for their herculean efforts to speak in laymen's terms. During one geology 101 lesson, Harry discovered I had a degree in geology and knew the difference between minerals olivine and plagioclase. An audible sigh of relief escaped him.

Up in the crater itself, we sat near the foot of the active dome. Rockfall off the over-steepened crater walls thundered down around us, and dust continuously was kicked up, while Norm explained to us the hazards of working in the crater. Surprisingly, volcanic hazards were on the bottom of his list. "First," he assured us, "was the danger of flying around frequently in a helicopter." The second and third dangers were rockfalls off the crater walls and dome walls. In fact, the team of scientists working in the crater were generally helicoptered from spot to spot around the crater to avoid rockfall. Finally, there was the danger from the volcano itself.

Don Swanson was of the identical opinion; this work was not particularly dangerous. We came upon him in the crater, and it struck me as odd to suddenly come upon someone sitting on a pile of wood in the middle of the volcano. There was something incongruously casual about this person, as if he were truly at home here! We quickly discovered that Don heads up the team that monitors the deformation of the dome for the USGS. The volcano has vital signs, similar to a human being, that play a major role in forecasting volcanic activity. Aside from seismicity, deformation was a most important clue. As Don explained his role in the studies, we observed two technicians "measure" deformation by measuring the distance between two points. These measurements are performed daily and generally vary by a few millimeters a day. Currently the dome is settling and moving outward. To forecast activity, they would expect to measure an increase in these rates of movement. In fact, deformation of the mountain before the May 18, 1980 eruption was remarkable. Prior to that date, a bulge developed on the north flank which moved outward at an average rate of five feet per day!

A variety of other studies are being undertaken also. These include determining the amount of widening of cracks in the dome and measuring the magnetic intensity of the rocks. Due to the number and the nature of investigations going on at Mount St. Helens, Don is confident that the USGS will be able to predict the next large-size event. He assured us that he feels safe near the dome and I believe him.

After Don's talk, we started the long hike back to our cars. It had been a most exciting, informative and exhausting day. Harrison Ford still failed to make his appearance, so I am reminded that reality is far more strange than fiction. And as for me, I returned to Mount Rainier with a healthy respect for all the Cascade volcanoes. They can be, after all, a blast!

Nancy Ward

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