When Mountains Come Tumbling Down   Leave a comment

When you travel in the west or most any mountainous region you often see signs warning of falling rock.  In many places you can see evidence of rock falls or the slightly softer version, avalanches.  Usually, no one is around to see or hear them.  Usually they are not very big though, of course, it only takes one rock to kill you.  On a previous trip I had visited Earthquake Lake in Montana, near Yellowstone.  Yellowstone has some sort of tremors ever day.  There is a lot going on under that place.  It is basically the home of a potential super volcano that were it to erupt at full intensity would devastate a large area in the middle of the continent.  Hopefully that is very far off, but there has been swelling that has increased in recent years.  At Earthquake Lake, often just referred to as Quake Lake, an earthquake of magnitude 7.5, which affected the entire Yellowstone area,  occurred in August of 1959.  Had it been the depths of the winter it might not have had the impact that it had.  This was not the case.  Eighty million tons of rock fall off the side of a mountain around midnight, completely blocking the river and surging with rock and water that killed 28 people camping in that area.  It is amazing to see huge boulders that traveled over 100 miles and hour across the valley and up the other side a huge distance from where it started and actually up hill on the other side.

The scar is clearly visible where the upper flank of Turtle Mountain collapsed in April of 1903.

 

Near Crowsnest Pass in Canada, the lowest pass across the lower Canadian Rockies, something similar occurred but for different reasons.  No earthquake was involved but the geology of Turtle Mountain was such that the layers of the rock were mostly vertical, with instabilities caused by erosion, water seeping, freezing and thawing and further destabilization caused by glaciers during the last ice age sheering off much of the bottom of the mountain’s support.  This was mining country, still is.  There were small camps, a railroad and other human fixtures in the area including a small town, Frank.  Frankly, those in Frank were rather lucky as it was mostly just beyond the area that was devastated when the entire side of the mountain fell off.  The area of rock was about a kilometer wide,  a kilometer  tall and had a thickness of around 150 meters.  That is a lot of rock.  Ninety people died, at least.  Miners within the mountain were, ironically, safe but did have to dig themselves out.  The tragedy could have been much greater if Frank, with roughly 600 residents, had been slightly farther to the East.  On April 29th, 1903, 82 million tons of rock fell fell of the mountain, quite comparable to the Quake Lake event.  The rock may have even floated along on a thin layer of compressed air and flowed almost like a river.  The flow buried two kilometers of railway.

A highway now cuts a narrow slice through the mile and a half long, 15 meter thick boulder field strewn far from where the rock perched before April 29th, 1903.

The slide is still very visible with the main southern  highway across the area cutting through the middle.  It is pretty obvious, if this happened again, paying attention to the “Falling Rock” signs is probably not going to do you much good.  Actually, those signs are more about fallen rock than falling rock anyway!  I think it is important to appreciate, when traveling, that what you are seeing hasn’t always been that way.  Those mountains often started out at the bottom of an ocean.  Those boulders once stood atop mountains.  Every so often, the events that create those vistas, canyons, waterfalls and other beautiful geological formations, also have had an impact on the people who passed that way before you.

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Posted July 28, 2012 by papaandnana in Uncategorized

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