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B.C.’s Rim of Fire sparks imaginations



Ever wondered why Black Tusk rises above the mountains as a dark jagged silhouette against a blue sky?

Local volcano expert Jack Souther can explain.

Souther blew away a packed house at Millennium Place during last week's slideshow presentation on local volcanoes.

He is the first speaker in a new monthly speaker series hosted by the Whistler Naturalists.

Along with the explosive history of Black Tusk, Souther also discussed the life span of other nearby volcanoes like Mount Cayley, Mount Fee and Meager Mountain, among others, which are collectively known as the Garibaldi Volcanic Belt.

His passion for the job has not waned in roughly 30 years studying volcanic rocks.

"They have left us with a legacy of beautiful and mysterious mountains," he said.

Before he talked about local volcanoes, Souther first took the crowd down elementary school's memory lane as he broke down the basics of volcano making, which he called Geology 101.

Dusting off old words like magma, mantle and crustal plates, Souther explained that the heat in the mantle and the movement of the earth's plates creates the driving force of volcanism.

Souther's modern day analogy of a volcano was a coke bottle which he began to shake.

He spared the audience the soaking by leaving the top on but they got the general idea of how volcanoes explode.

While volcanologists can look back at history with clarity and explain why and how volcanoes erupted, they are less sure about volcanic activity in the future, he said.

"We still have little ability to predict when they will erupt and almost no ability to control them (when they do erupt)," he said.

B.C. lies on the cusp of a hotbed of volcanic activity as about two-thirds of the earth's volcanoes are in and around the Pacific Ocean, commonly known as the Pacific Rim of Fire.

Years ago people believed Canada was a gap in the Rim of Fire because the volcanoes along the Canadian West Coast did not look like the volcanoes in other parts of the rim.

Subsequent analysis of the mountains showed Canada's volcanoes took on a different look mainly due to the fact that they erupted under or onto ice.

After the basics of volcano making were covered, Souther then moved the slideshow presentation to pictures taken at the top of Blackcomb Mountain.

Facing south, Black Tusk rears out of the mountains as one of the most conspicuous volcanoes in the area.

It is also one of the oldest.

It was created over a long period of time. The first stage was built about 1.3 million years ago; the latest action was about 170,000 years ago.

Souther described Black Tusk as a conventional volcano with a central core of lava.

Stone and ash encased this central core, and eventually this casing was not strong enough to withstand erosion through periods of ice.

The distinctive shape that is Black Tusk today is what is left of the central core.

Back on the top of Blackcomb, again looking south, the slide showed the summit of Mount Garibaldi.

Throughout Mount Garibaldi's history, there were dramatic climatic events in the area with the ebb and flow of glaciers.

Garibaldi's main summit erupted onto the ice, whereas the Table erupted into the ice and formed a tuya.

Tuyas are made when lava is unable to punch through ice and so it forms beneath. The result is a flat shape much like a table.

Souther also talked about geological hot spots below the earth's surface at Meager Mountain and Mount Cayley.

At the moment, drills continue to plunge into the earth at Meager Mountain, to scope out geo-thermal potential.

Mount Cayley is a different story.

Souther isn't overly concerned about the hot spots at Cayley, which is his favourite local mountain.

But these hot spots show volcanologists that the roots of some of the volcanoes are still pretty hot.

"This doesn't mean that Mount Cayley will erupt in 2010. That would be a real downer, wouldn't it?" he joked.

So while there will be no burning lava spewing out of Whistler's mountains in the foreseeable future, the mystery of volcanoes still fires imaginations, he said.

It was certainly enough spark to pack the house at Millennium Place.

"It's not often we get this big a crowd for an earth science lecture," joked Bob Brett, president of the Whistler Naturalists.

Next month's speaker is John Clegue, a professor of glaciology at UBC. He will be taking about the Ice Age and its effects on the Whistler area.

This talk will take place on April 25 at 7:30 p.m. at Millennium Place.

The speaker series will continue each month.