April 01, 2011 Features & Images » Feature Story

Life after lava 

The surprising biodiversity of Mount St. Helens post-eruption


High Country News

Editor's Note: The Pacific Ring of Fire is a 40,000 kilometre-long belt of geological features looping around the Pacifc Ocean, created by the continual movement of the earth's tectonic plates. It's comprised of volcanic zones and oceanic trenches stretching from the northeast coast of New Zealand to the Kamchatka peninsula of Russia in the north; across the Aleutians to Alaska and back south again along the coast of North and South America to the southern tip of Chile. It affects New Zealand (earthquake measuring 6.3 on the Richter Scale on Feb. 22, with almost 350 deaths) and Japan (earthquake on Mar. 11 measuring 9.0 unleashes a tsunami, up to 30,000 killed). In March 2010, Chile experienced a pair of strong quakes (8.8 and 6.3) that unleashed a tsunami that left hundreds dead and thousands more homeless.

The simple explanation for all this shaking is that the tectonic plates are continually in motion, pulling, pushing and shifting around one another. When one plate pushes up against another, the pressure builds until something has to give. That pressure pushes up mountains, but it can also lead to quakes and the formation of volcanoes - which often take the appearance of mountains, with a recognizable conical shape.

There is evidence of volcanism all over the coast of B.C. and close to Whistler as part of the Garibaldi Volcanic Belt (which is part of the larger Cascade Volcanic Arc).

Right now the main risks seem to be landslides and flooding when loose volcanic materials slump into waterways and allow water to build up behind them. Just last summer, Pemberton was put on alert after heavy rains triggered a major landslide in the still volcanic Meager area, creating a natural dam with a massive lake behind it. The dam eventually disintegrated, but the worst-case scenario was a sudden release of a large amount of water.

For years B.C. has also been preparing for a large earthquake that geologists are certain is coming, and that some believe is probably overdue.

While it's possible that some moderate quakes could occur in the Georgia Strait between Vancouver Island and the mainland, the real risk is for a quake up to 9.0 - the size of the one that hit Japan on Mar. 11 - off the west coast of Vancouver Island.

Generally speaking, most of the volcanoes in the region are dormant and pose little risk.

Volcanism in the region is the result of the Pacific Oceanic Plate pushing the Juan de Fuca Plate under the North American Plate, which causes pressure to build up in the earth's crust. That pressure bubbles up to the surface, following fractures and volcanic vents, until we see an eruption.

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