A New Glacier Grows at Mount St. Helens

“I grew up in the Yakima Valley (near Mount St. Helens). I was out fishing when I saw the lightning and dark cloud,” Flickr user vmf-214, who captured the eruption of Mount St. Helens in 1980, told GlacierHub. “It looked like a storm. I saw it as I pulled into the yard. Mom came out and said the mountain had blown.”

A major volcanic eruption occurred at Mount St. Helens in 1980 (source: vmf-214/Flickr).

He was describing the volcanic eruption that occurred at Mount St. Helens 37 years ago in May 1980. During that event, an eruption column rose into the sky, ultimately impacting 11 states in the U.S. But it wasn’t just the people who live in the area that were affected by the eruption: the glaciers of Mount St. Helens melted into nearby rivers, causing several mudslides.

Cascades Volcano Observatory indicates that before the 1980 eruption, extensive glaciers had covered Mount St. Helens for several hundred thousand years. About 3,900 years ago, Mount St. Helens began to grow to its pre-eruption elevation and a high cone developed, allowing for substantial glacial formation. There were 11 major glaciers and several unnamed glaciers by May 18, 1980, according to the United States Geological Survey. But after the eruption and resultant landslide, about 70 percent of the glacier mass was removed from the mountainside. It was during the winter of 1980 to 1981, following the catastrophic eruption, that a new glacier, Crater Glacier, first emerged.

An aerial view of the crater (source: Geography Review).

“The glacier formed very fast, in a couple decades,” professor Regine Hock from the University of Alaska – Fairbanks told GlacierHub.

It developed in a deep crater left by the eruption and landslide. Rock debris from the crater walls and avalanche snow created a thick deposit between the 1980–86 lava dome and crater walls. Shaped like an amphitheater, the crater protected the glacier from sunlight, allowing the glacier to expand extensively, according to the USGS. By September 1996, it was evident from photographs and monitoring that a new glacier had formed. Crater Glacier at Mount St. Helens is now considered one of the youngest glaciers on Earth.

“The glacier tongues can be seen, descending either side of the degassing cone. Much of the glacier is covered by volcanic ash,” notes a recent report in Geography Review. By 2004, the report continues, the glacier covered around 0.36 square miles (0.93 km2), with two lobes wrapping around the lava dome in a horseshoe-like shape.

A bulge in Crater Glacier next to the south side of the 1980–86 lava dome in 2004 (source: D. Dzurisin, USGS/Walder et al.).

Joseph S. Walder, a research hydrologist at the USGS, has been studying the latest eruptions of Mount St. Helens. When interviewed by GlacierHub, he attributed the formation of the Crater Glacier to three factors.

“First, the crater acts as a sort of bowl that collects snow avalanching from the crater walls, so the accumulation rate is extremely high,” Walder said. “Secondly, the crater floor is in shadow most of the time. Last but not least, lots of rock material avalanches onto the crater floor, tending to cover and insulate accumulating snow.”

The new lava dome of Mount St. Helens and the by-then morphologically distinct east Crater Glacier (in foreground) in 2005 (source: J.W. Vallance, USGS/Walder et al.).


Today, there are hiking tours available throughout the Mount St. Helens area. Climbing the mountain is like walking on the moon, with ash and boulders surrounding you. From the top, you can see the growing volcanic dome, steaming and smoking.

Rodney Benson, an earth science teacher and blog writer at bigskywalker.com, hiked into the crater recently. “Some say the world will end in fire. Some say ice. What does this new glacier indicate?” he pondered.

Hike into Mt. St. Helens (source: buen viaje/Flickr).

 

As glaciers around the world recede as a result of climate change, the new glacier provides a fascinating context to explore interactions between volcanic processes, volcanic deposits and glacier behavior. The intensive monitoring programs led by the USGS have allowed us to observe these processes in unusual detail.

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