Geologist Tom Pierson '70 walks the volcano beat. And his work saves lives.
By Marc Covert
It seems odd, at first, to learn that the David A. Johnston Cascades Volcano Observatory is a one-story, nondescript building nestled in a sprawling Vancouver, Washington, office park, a good 50 miles south of its star subject: the continental U.S.'s most active volcano, Mount St. Helens. And then you're reminded of the observatory's namesake, geologist David Johnston, and his frantic radio transmission on the morning of May 18, 1980—"Vancouver, this is it!"—just before an enormous lateral blast of hot gas, steam, and rock debris, traveling upwards of 600 miles an hour, engulfed him at his observation post five miles from the volcano's peak. On second thought, it makes sense that those entrusted to scrutinize the infamous volcano are close enough to make field surveys, yet safely removed from immediate danger should catastrophe return.
Well, St. Helens is rumbling again, the media's interest is piqued, and the Pacific Northwest is jittery. At the confluence of this brewing storm of science, interest, and fear is Tom Pierson '70, a research hydrologist with the U.S. Geological Survey.
He and his colleagues' behind-the-scenes role in the study of volcanoes was abruptly thrust front and center when St. Helens awoke on the evening of September 22, 2004. "We had no lead-up; it came completely out of the blue," he says. "However, it is the most active volcano in the Cascades mountain range, so it wouldn't be right to say it was a complete surprise."
Earthquake swarms—when a large number of earthquakes occur in a short period of time—were detected beneath St. Helens on September 23; three days later, a "notice of volcanic unrest" was issued, designated as level 1 on a three- point scale. On September 29, the USGS raised the alert level to 2, indicating "concern that current unrest could culminate in an eruption." An onslaught of media attention ensued, and Pierson, a USGS point person on the dangers communities face if a volcano erupts, became a must-get interview for journalists worldwide.
Pierson specializes in the study of lahar flows: volcanic mudflows consisting of sediment, rock, debris, and water, "basically, wet mucky stuff that slides off the sides of volcanoes," Pierson explains. "Lahars are a saturated mixture of water, rock, and soil; they occur in mountains everywhere, and they're very destructive."
So destructive that lahar flows are one of the gravest dangers a community can face when a volcano erupts. Lahars can crush anything in their path and are capable of burying entire communities under layers of thick, cement-like debris. (In the 1991 eruption of Mount Pinatubo in the Philippines, 700 people were killed by lahar flows.) For this reason, Pierson's greatest responsibility before a volcano erupts is to forecast where the danger zones will be for the nearby community. When a level 3 alert is reached, Pierson immediately informs the various municipalities what their risks are. Factors such as historical precedent, mountain topography, current climate, and the density of erupting rock fragments and hot gases are all taken into account.
Prompted in early October by another series of earthquakes—harmonic tremors, which indicate the movement of magma toward the surface—scientists raised the alert to 3, necessitating the evacuation of 2,500 people. Steam and ash eruptions continued, but a blast never came; the alert was lowered to 2 when the quantity and severity of earthquakes dropped.
While the steam plumes are dramatic, Pierson is more interested in what's going on inside and underneath the crater, where lava-dome activity is being detected for the first time since 1986. A second dome is rising now, pushing up on a horseshoe-shaped glacier on the floor of the crater, splitting it in two. Pierson is watching to see if the hot lava will cause a sudden, catastrophic meltdown of the glacier. Clearly, St. Helens is still very much in the spotlight, and Pierson's job is what he calls "any geologist's dream."
Growing up in Pennington, New Jersey, Pierson was a self-described naturalist, constantly exploring the woods, fields, and streams of his rural town. When the time came to choose a college, he was sold on Middlebury, primarily by its location in the Champlain Valley. He selected German as his major, but late in his second year, he began to think about following a different track. In the spring, he audited a geology course and was smitten. "I sat in on it just for fun—I did all the work, went on all the field trips, did all the exercises; I just loved it. By the end of that semester I had decided to switch majors."
After graduating, he spent a summer as a field assistant in New Mexico for Professor Peter Coney, and later earned advanced degrees in geology; he was working in a post-doctoral position in New Zealand when St. Helens blew. Half a world away, Pierson heard only sporadic reports of the event, but a few weeks later he was in Seattle for a wedding and couldn't resist driving south to have a look at the devastation.
"I could see all the damage done by the debris flows," he says. "I was fascinated by what had happened. This enormous lahar had flowed over 70 river miles and emptied enough material into the Columbia River to block its shipping lane."
Pierson had a résumé with him, and he dropped it off at the USGS office in Vancouver on a lark. He returned to New Zealand, but in October the USGS called and offered him a job. He relocated that winter.
Though his base is in the Pacific Northwest, Pierson has traveled around the globe to study numerous volcanoes in far-flung locations. He's learned that minor eruptions can trigger catastrophic lahars (the surface area of snow on an icecap, the entrainment of eroded sediment, the presence of velocity-inducing valleys are all critical components), and he uses this information to inform communities located downstream of volcanoes, in hot spots worldwide.
In his office, Pierson is surrounded by books, rock samples, computers, and family photos. He's soft-spoken and self-effacing when responding to questions about himself, but he becomes animated when questioned about his work.
"What I've always liked about geology is that I get to be a detective, looking at clues—it's the ultimate cold case," he says. "The fun is in answering questions by collecting data, trying to figure out what happened. What I find rewarding is that I can take that detective work and put it to use in dealing with ongoing volcanic hazards around the world today."
Pointing to a wall-sized photo of the Mount St. Helens crater, he continues: "For example, we know that, once triggered, lahars can flow around a lava dome like this and go straight down the side of the mountain. We don't tell people what they should do, but we try to give them information so then they can make up their own minds as to how much risk they're willing to accept. So the work we do here is at the very forefront of the field and has far-reaching benefits for people around the world."
Marc Covert is a freelance writer in Portland, Oregon.