Scientists are trying to reconstruct what the environment and climate of southwest British Columbia looked like over the past two million years by studying volcanoes that erupted under the glaciers.
Alex Wilson, a University of British Columbia PhD student and part of the research team, said in order to make predictions about the climate in the future, scientists need to understand the past.
He uses a combination of field analysis and radiometric dating to calculate when an eruption occurred and if it was beneath ice to infer what was happening with the climate going back millions of years.
“We want to understand how ice sheets have behaved in British Columbia in the past because we want to know how the glaciers in British Columbia grow and retreat in relation to the glaciers of the rest of the world,” he said.
Research so far has shown that large ice sheets have expanded or melted many times over two million years, said Wilson, who is conducting the study with his supervisor at the university, volcanologist Kelly Russell.
Wilson said most existing climate records using ice cores in Greenland and Antarctica only go back 400,000 years but earlier information could help predict what’s in the future as Earth’s climate changes.
“One reason that we are so worried is that we don’t know what will happen. But there are clues in the ancient history of the Earth. The climate has fluctuated in the past, many times in the past. It has been colder and warmer than it is now.”
Wilson said the Garibaldi Volcanic Belt, along B.C.’s Sea to Sky corridor north of Vancouver, has seen warm periods and times when the volcanoes were buried under ice sheets.
More than 100 volcanoes have erupted either close to or under the ice over the last two million years, he said.
And when volcanoes erupt beneath glaciers the surrounding water causes them to behave in strange ways. Volcanoes are more explosive and ice can freeze the flow of lava, creating unique geological features. he said.
“The rocks that we see are a little different. They are complicated,” he said. “They show evidence for interacting with a lot of water when they erupt.”
By looking at the rock formations, Wilson and Russell have been able to provide evidence of at least three ancient so-called glaciations over the past one million years, where large ice sheets covered the southwest part of B.C.
“We have very special volcanoes that there aren’t examples of these anywhere else in the world. They are unique to British Columbia.”
One of the best examples of these strange formations is the flat-top, steep-sided volcano known as The Table, not far from Garibaldi Lake. It erupted about 100,000 years ago, he said.
“There aren’t any other examples of The Table anywhere else in the world,” Wilson said. ”It doesn’t look like a typical volcano, like a cone or a crater.”
The warming climate has also uncovered new information for researchers, Wilson said.
“A lot of the glaciers are melting very rapidly in B.C. They are retreating back and those glaciers are exposing rock that we haven’t seen before,” he said. “We have actually discovered a number of new volcanoes we didn’t know about.”
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Wilson is also trying to understand if growing and retreating ice sheets could trigger or cause volcanic eruptions.
Ice sheets are extremely heavy, which can stress the Earth’s crust and influence how magmas move through the crust, he said.
“There was once two kilometre of ice loaded on southwestern B.C.”
There is compelling evidence in Iceland to suggest that melting glaciers cause an eight-fold increase in volcanic eruptions, he said.
“Could this be the case for southwest B.C.? We think it might be and we are trying to prove it. Here’s another catch, could melting glaciers that currently exist in B.C. cause more volcanoes to erupt? We are trying to find out.”
The last eruption in the Garibaldi Belt was 2,360 years ago, relatively recent in geological terms, but still indicating the area is dormant, he said.
“But it’s by no means an extinct volcanic area,” Wilson said. “I’m not saying there’s going to be an eruption tomorrow but more than likely there will be eruptions in the future.”
Hina Alam, The Canadian Press