23 November 2012

Boulders!

Posted by dr-dave

In the last few days there have been several interesting incidents involving boulders on various scales:

1.  A small boulder movement in Bath, England

The spell of exceptionally wet weather in the Uk over the last few months continued yesterday (and there is more due tomorrow) with a very intense low pressure system bringing very heavy precipitation.  In the beautiful city of Bath, a boulder was dislodged and rolled about 20 m downhill overnight.  This was quite small, but still had an estimated mass of about 3 tonnes:

http://www.itv.com/news/west/update/2012-11-23/landslip-in-bath-releases-huge-boulder/

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The boulder has a rather strange shape, so I’d be interested to hear what it is made from.

On a slightly larger scale, James Glover, a PhD student here at Durham, drew two really ice examples from Europe last week to my attention:

2. A large boulder fall in Switzerland

In Switzerland last week an 80 cubic metre boulder fell onto Julierstrasse between Rona and Mulegns.  James passed on to photos that Maja Bless took of the boulder and its source / track:

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3. A very large boulder fall on the Gotthard Tunnel rail line.

(And many thanks to a few other people for highlighting this one too).  Last Wednesday a huge boulder fell onto the Gotthard Tunnel railway line in Switzerland.  This Swiss article provides the details in German, but in a nutshell about 70 cubic metres of rock came down and landed on the track, which was blocked until last Monday.  This is a screen grab from that article – I suspect that the designers of the rock catch fence didn’t quite anticipate that their design would be tested to this extent:

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This site has suffered repeatedly from landslides this year, but it may well have been that the geologists found it very difficult to assess the stability of a block this large.