MOUNT ST. HELENS – Standing on Mount St. Helen’s southern rim, Cynthia Gardner sees much more than a smoldering volcano. Like her colleagues at the U.S. Geological Survey, Gardner sees an enormous gift basket packed with scientific marvels.
She finds the ongoing eruption and burgeoning lava dome fascinating enough, but she sounds almost giddy when she talks about the crater’s glacier.
“The glacier is mind-bogglingly cool,” said Gardner, a USGS geologist, “maybe even more interesting than the eruption.”
Ever since St. Helens rumbled back to life in 2004, geologists have curiously watched the dichotomy of fire and ice play out. It’s mesmerized them, surprised them and now is threatening some of their seismic monitoring equipment.
Crater Glacier is like no other glacier in the world. It’s the only glacier with lava extruding through it and forming a dome. And while most glaciers are receding, Crater Glacier is advancing three feet per day and forming a collar around the growing dome.
What will happen next as the glacier and the dome continue to grow and try to claim their share of the crater? Scientists wish they knew.
“It’s still an empirical science,” Gardner said last week. “We are learning from what we see.”
Crater Glacier started forming shortly after St. Helens blew its top on May 18, 1980. The glacier is fed by snow and falling rock and ice from the crater rim. The glacier is about 40 percent rock and 60 percent ice, USGS geologist Willie Scott said.
Originally, the glacier filled the void between the crater walls and the lava dome that formed from 1980 to 1986. Peter Frenzen, Mount St. Helens National Volcanic Monument’s scientist, says the crater’s architecture is perfect for nurturing the glacier.
The crater floor is 6,500 feet above sea level, high enough to collect plenty of snow. And the 1,800-foot-tall crater walls and the lava dome give the glacier ample shade.
But when the 2004 eruption pushed a new dome up through the ice, something had to give. Geologists feared the 1,300-degree lava would melt the glacier, causing a lahar to spew from the open end of the horseshoe-shape crater.
What happened next surprised the scientists.
Cooling rock on the outside of the dome insulated the glacier from the lava, and only about 10 percent of the glacier melted, said Carolyn Driedger, a USGS hydrologist. Instead, the dome, growing by a pickup truckload of lava every two seconds, split the glacier into two moraines – deposits of glacial rock and soil – pressing each against the crater walls. The pinching forced the glacier arms to double in depth and increase their speed.
The arms, which are as deep as 500 feet in places, are just 400 feet away from colliding on the northern side of the dome. Using a GPS unit placed on the glacier, scientists estimate it’s moving three feet per day and that the arms will meet later this year.
In the glacier’s path is the Yellow Rock seismic station, which has recorded St. Helens’ belchings since 1981. In anticipation, geologists put a replacement station outside the glacier’s path in 2006.
Geologists say the dome’s slow pinch on the glacier shows no signs of stopping. Gardner and Scott point to Guatemala’s Volcn Santa Mara as an example of how long St. Helens might erupt. Santa Mara has been erupting since 1922.
At its current rate of growth, the dome will rebuild St. Helens to its pre-1980 glory in 180 years.
Depending on whom you ask, Crater Glacier might not be around to see that day. Scott says the glacier is on a suicidal path. As its moraines are pinched off and reach lower and warmer elevations, Scott envisions the glacier stagnating and melting.
Driedger doesn’t think the glacier will ever be entirely pinched off by the dome. She thinks the glacier will rise higher as the crater fills in and finds a home on the dome.
“But it’s conjecture on all our parts,” Driedger said. “That’s what makes this so fun to watch. As scientists, we might be taking measurements, but we don’t know the end of the story.
“We’re like everybody else, watching to see what story the mountain tells.”
CRATER GLACIER BY THE NUMBERS
Feet the two arms of the glacier move each day.
Width in feet of the glacier’s west arm. The east arm is 790 feet wide.
Estimated depth in feet of upper glacier. The lower glacier is 60 to 130 feet deep.
Feet the glacier arms must travel before they reunite on the north side of the dome. Scientists think that will happen this year.
Area of glacier in square miles, more than twice that of Mount Hood’s White River glacier.
Source: U.S. Geological Survey
GIVE MOUNTAIN A GO YOURSELF
$22 per climber. All permits must be bought at mshinstitute.org
12 climbers per party. One hundred climbers allowed on the mountain per day. Most weekend permits are sold out through Sept. 22.
St. Helens is currently erupting but is considered safe for climbing.
The route gains roughly 4,500 feet and is 10 miles roundtrip.
In addition to climbing gear, officials recommend a dust mask, goggles and, in the unlikely event of an explosive eruption, a climbing helmet.
Online: Visit mshinstitute.org
or go to www.fs.fed.us/gpnf/
and click on “Mount St. Helens climbing permits.”