2008 Yukon Nuggets

Mount Churchill

It was so remote that no one had ever heard of it. Even today, Mount Churchill is seldom seen and rarely explored. But this giant mountain in the St. Elias has certainly left its mark on the Yukon. Located 25km west of the Alaska-Yukon border in the Wrangell St. Elias National Park, Mount Churchill is more than 15,000 feet high, and permanently covered with ice and snow. The first explosion that blew the top off the mountain occurred about 1900 years ago, when volcanic ash was sent flying over northwest Alaska, landing as far away as Eagle. Then, 1250 years ago, Mount Churchill erupted again in a much larger explosion, which blew the lid off the mountain, and carried the ash into the southwest Yukon. It’s known as the White River Ash, and covers almost 600,000 square kilometers in Alaska, the Yukon, and the Northwest Territories. Along roadways it appears as a thin white line close to the surface. However, closer to the volcano, the ash can be 60cm thick. The ancient ash is well preserved, leading scientists to believe that the explosion occurred in the winter because it was immediately frozen and protected by a layer of snow. People and wildlife living in the southwest Yukon at the time would have been well aware of the eruption, and may even have heard it, but they would have no idea of its source. The ash would have killed vegetation in the area, making it difficult for people living on the land, and would have darkened the skies for weeks, if not months. So massive was the explosion that anthropologists think it could have caused the migrations from the north that eventually led to the formation of Athabascan cultures, such as the Apache and Navajo in the southwestern United States.

Mount Churchill, the source of all the misery, has been inactive for a long time because it has a thick magma, and takes a while to build up pressure before exploding again. Volcanoes of this type tend to erupt in 100 to 1000 year cycles, so it’s an open question as to when the mountain may blow its top again. But it will, and when it does it will have a significant economic impact on Canada. It could obstruct air travel, trigger mudslides and floods in the region, and cover a large area with more white ash. Although southwestern British Columbia and the Yukon have not experienced a major volcanic eruption in a long time, the potential for future activity remains. A volcano can be dormant for many centuries while gas pressure slowly builds up in its subterranean chambers. Mount Churchill in the St. Elias is certainly a candidate for a future catastrophic event.

 

A CKRW Yukon Nugget by Les McLaughlin.