27 April 2011
In the last few days a series of new videos have emerged of landslides and rockfalls as they occur. Thanks to various people for highlighting them to me. I am still struggling with the WordPress embed function (it was so easy in Blogger!), so apologies that some of this will have to be done through external links.
First, a couple of weeks ago a debris flow killed 20 people when a small bus was carried into a ravine near to the city of Manizales in Colombia. In the last 24 hours a video has emerged on Liveleak that reportedly shows the landslide further up the slope. It is not clear to me that this is the same event, but the footage is certainly dramatic, not least because it is clear that it was unexpected. The video is available here. One interesting aspect is the clear illustration of the dangers of being inside a building when such an event occurs – witness the way that the slide passes through the building and then out of the windows.
Second, and on a very different scale, Garry Hayes of the excellent Geotripper blog caught on camera a small but technically interesting rockfall event near to Yosemite last week, which can be viewed at this link. Helpfully there are several photographs of the site too, taken both before and after the slip.
Thirdly, thanks to Lisa Denke for bringing this remarkable video of a rockslide in Wyoming to my attention. This one should embed, but if not it can be viewed here, and there is a commentary here. You may want to turn the sound down before you play it though!
The person who captured the video had a very lucky escape – there is not much doubt that being struck by that debris would not have been survivable. However, look carefully at what happened before the main slide event. There is extensive precursory rockfall activity on both margins of the landslide, which I would suspect occurred as creep in the main mass caused extensive shearing in this area. One of the best aspects of these videos in recent years has been the ways in which they have highlighted the role of precursory activity.
Finally, thanks to Kevin Nelstead of the interesting (and thought-provoking to me as a committed atheist) Geochristian Blog for highlighting some fascinating coverage of the removal of dangerous boulders from the Rimrocks in Billings, Montana. There is an excellent set of resources on the website of the Billings Gazette, including:
A video of the boulder from the toe of the slope (anyone want to buy a second-hand camera – it might be slightly dented?). This is rather good, but I cannot work out how to embed it at the moment.
A video of the removal process from the side, which should embed below:
This pair of videos illustrates beautifully the importance of the rolling motion of large blocks in the rockfall runout process.