Fellow geo-blogger David Petley of Durham University posted today about the 105th anniversary of the Frank Landslide in Canada. The slide had an estimated volume of 30 million cubic meters and took all of about 100 seconds to travel down the mountain and engulf a portion of a nearby coal mining town. 76 people were killed, and a number of bodies were never recovered because of the massive amount of material. Since 2003, they have installed real-time monitoring equipment to warn if the mountain fails again, which seems likely based on an interesting video (requires Windows Media Player). It shows some of the massive tension cracks at the top of the limestone mountain. (Photo by Natural Resources Canada by way of Dave’s Landslide Blog)
Earlier this month, there was a massive slope failure on the "Sea to Sky" highway in British Columbia. It is interesting to note that this same area had a large rockslide in 1965, and a photo of this failure is featured on the cover of the classic text, Rock Slope Engineering by Hoek and Bray. The media played up the aspect that this highway is one of the only ways to access the site of the 2010 Winter Olympic games hosted by Vancouver.
The composite image above shows the book cover and the recent rockslide event (Photo credit: Erik Eberhardt of the University of British Columbia by way of Dave’s Landslide Blog). Dave has done a fabulous job collecting photos, facts and links from around the web. In a follow up post, he added some additional photos and discussion. I recently came across an article that described how the highway originally was slated to have a tunnel bypassing the slide, but that the price tag of $200 million (CAN?) for a 1-km stretch killed the project.
The Utah Geologic Survey has released a "Landslide Susceptibility Map of Utah". They apparently relied quite heavily on GIS based thresholding of existing slope angles but only after they had statistically analyzed failure angles for particular geologic units. So it sounds like they throw the known landslides, the geologic map of Utah and a DEM into the GIS a blend it all up. Perhaps a slight oversimplification!