Hawaii's Kilauea volcano raises concerns of eruptions along West Coast

The eruption of a Hawaii volcano has people warily eyeing volcanic peaks on North America's West Coast.

The coast is home to a chain of 13 volcanoes from Washington state's Mount Baker to California's Lassen Peak. 

They include Mount St. Helens, whose spectacular 1980 eruption in the U.S. Pacific Northwest killed dozens of people and sent volcanic ash across the country, and massive Mount Rainier, which towers above the Seattle metro area.

Farther to the north, British Columbia and Yukon host five volcanic belts, which have seen at least 49 volcanic eruptions over the last 10,000 years, according to Natural Resources Canada.

The peaks are part of the "Ring of Fire," volcanoes that sit on tectonic plates. Hawaii is not part of the Ring of Fire.

All our mountains are considered active and, geologically speaking, things seem to happen in the Northwest about every 100 years.- John Ufford,  Washington Emergency Management Division

"There's lots of anxiety out there," said Liz Westby, a geologist with the U.S. Geological Survey Cascades Volcano Observatory in Vancouver, Washington. "They see destruction, and people get nervous."

Kilauea, on Hawaii's Big Island, is threatening to blow its top in coming days or weeks after sputtering lava for a week, forcing about 2,000 people from their homes, destroying two dozen homes and threatening a geothermal plant. Experts fear the volcano could hurl ash and boulders the size of refrigerators miles into the air.

What is the Ring of Fire?

Roughly 450 volcanoes make up a horseshoe-shaped belt that follows the coasts of South America, North America, eastern Asia, Australia and New Zealand. It's known for frequent volcanic and seismic activity caused by the colliding of crustal plates. Kilauea is situated in the middle, on a different tectonic fault or volcanic hotspot.

The most dangerous volcanoes in the U.S. are all part of the Ring of Fire, and most are on the West Coast, according to the U.S. Geological Survey. Besides Kilauea, they include: Mount St. Helens and Mount Rainier in Washington; Mount Hood and South Sister in Oregon; and Mount Shasta and Lassen Volcanic Centre in California.

In Canada, the most recent eruption occurred about 150 years ago at Lava Fork, which is located in northwestern B.C. The last time a major eruption shook this part of the world was more than 2,300 years ago at Mount Meager in southern B.C., Natural Resources Canada says.

Images of lava flowing from the ground and homes going up in flames in Hawaii have stoked unease among residents  along the Ring of Fire. But experts say an eruption on one section of the Pacific doesn't necessarily signal danger in other parts.

"These are isolated systems," Westby said.

When will the West Coast volcanoes erupt?

No eruption seems imminent, experts say.

The Cascades Volcano Observatory monitors volcanoes in the Pacific Northwest and posts weekly status reports. All currently register "normal."

But the situation can change fast.

"All our mountains are considered active and, geologically speaking, things seem to happen in the Northwest about every 100 years," said John Ufford, preparedness manager for the Washington Emergency Management Division. "It's an inexact timeline."

Some geologists believe Mount St. Helens is the most likely to erupt.

But six other Cascade volcanoes have been active in the past 300 years, including steam eruptions at Mount Rainier and Glacier Peak and a 1915 blast at Lassen Peak that destroyed nearby ranches.

What kind of damage could they do?

The Big Island scenes of rivers of lava snaking through neighbourhoods and sprouting fountains are unlikely in the U.S. Pacific Northwest.

"Lava is not the hazard, per se, like in Hawaii," said Ian Lange, a retired University of Montana geology professor. Cascade volcanos produce a thicker, more viscous type of lava than Hawaiian volcanoes, so it doesn't run as far, Lange said.

But Cascade volcanoes can produce huge clouds of choking ash and send deadly mudslides into rivers and streams. Two of the most potentially destructive are Mount St. Helens, north of Portland, Ore., and Mount Rainier, which is visible from the cities of Seattle and Tacoma.

Mount Rainier eruptions in the distant past have caused destruction as far west as Puget Sound, some 80 kilometres away.

The volcano hasn't produced a significant eruption in the past 500 years. But it remains dangerous because of its great height, frequent earthquakes, active hydrothermal system and 26 glaciers, experts said.

An eruption on Mount Rainier could rapidly melt glaciers, triggering huge mudflows — called lahars — that could reach the densely populated surrounding lowlands, Westby said.

Another major danger from a Cascade volcano eruption would be large amounts of ash thrown into the air, where it could foul aircraft engines.

What are communities doing to prepare?

The closest settlement to a volcano along the U.S. West Coast may be Government Camp, on Oregon's Mount Hood. Lava could conceivably reach the town, but the greater threat is an eruption triggering a so-called pyroclastic flow, which is a fast-moving cloud of hot ash and gas, experts said.

But Lange believes California's Mount Shasta is the most dangerous, in part because it is surrounded by towns.

The town of Mt. Shasta has numerous response plans for emergencies, including a volcano eruption, Police Chief Parish Cross said. But the plan for a volcano is pretty fluid, he said.

"We don't know the size or scope of the event," Cross said, including which direction the eruption would occur.

This is not an issue in Orting, Wash., about 32 kilometres west of Mount Rainier. Orting would be directly in the path of a lahar, and local officials each year conduct drills in which children move from school to higher ground to escape the flow.

Students usually take about 45 minutes to walk the three kilometres to higher ground, which should be fast enough to escape, officials said.

"Our concern is ice and snow melting rapidly on Mount Rainier," said Chuck Morrison, a resident of the town of 7,600 who has long been involved in evacuation planning. "We need a quick way off the valley floor."

Orting is the town most vulnerable to lahar damage from Mount Rainier, according to the U.S. Geological Survey.

Scientists say that in the worst case, a 9-metre-high lahar with the consistency of wet concrete could rumble through Orting at 80 km/h if volcanic activity suddenly melted snow and ice on Rainier.