Video of the Rest and Be Thankful landslide site in Scotland

The BBC has a short video on its website of the Rest and Be Thankful landslide site in Scotland. It can be found here.

New landslide at the Rest and Be Thankful in Scotland

Probably the most infamous landslide event in recent years in the UK occurred in Scotland in August 2004 when a series of landslides occurred, including one on the A83 at the rather delightfully named "Rest and Be Thankful". The same area was affected again by landslides in 2007. The images from the time were quite spectacular, as shown by the BBC at this web page, which is the 2007 slide:

The slide here, and several other slides on the same day in 2004, prompted quite a major study into landslides on the Scottish Highway system. The report is online here.

The BBC is this afternoon reporting that the road is once again blocked by landslides.:

"A long stretch of the A83 has been shut after a landslide at the Rest and be Thankful road, west of Loch Lomond. Police said westbound traffic was being diverted at Arrochar while eastbound traffic was being diverted at Inverary. According to reports, some heavy vehicles are stuck in mud which has come down from the hillside."

For those interested there is a nice background to the 2004 events here, whilst the BGS have information on the 2007 landslide here.

August 2009 fatal landslide map

Here is the fatal landslide map for August 2009. As usual each yellow dot represents a single landslide that killed one or more people:

Click on the map for a better (downloadable) view in a new window.

The statistics are as follows:
Number of recorded fatal landslides: 53
Number of fatalities: 782

In terms of fatalities this places August well above the 2002-2008 average (347 fatalities). Of course this is dominated by Typhoon Morakot in Taiwan, and in particular the landslide at Hsiaolin. However, the map shows clearly the impact of the SW monsoon along the southern edge of the Himalayas and also the impact of typhoons in E. Asia. Elsewhere there is the normal smattering of landslides here and there. The lack of slides in S. America is perhaps surprising. The paucity of hurricanes in the Caribbean means that this area is not figuring at the moment. I wonder if we will see a large, late season event.

Oh dear, more scientific hyperbole about climate change and natural disasters

My Alma Mater, University College London, is this week hosting an interesting colloquium on the theme of "Climate Forcing of Geological and Geomorphological Hazards". This is a really interesting topic and the organisers should be applauded for attracting some really interesting talks. If it wasn't for the fact that I am heading out to Asia on Wednesday I would attend for sure. However, the Observer, which is the Sunday version of the UK broadsheet newspaper The Guardian, has today run a two page story about the conference. Again, this is not unwelcome - it is important that articles are run about the multi-faceted implications of climate change - but unfortunately the tone of the headline and lead material is an example of scientific hyperbole has left me speechless:

Climate change: melting ice will trigger wave of natural disasters
Scientists at a London conference next week will warn of earthquakes, avalanches and volcanic eruptions as the atmosphere heats up and geology is altered. Even Britain could face being struck by tsunamis.

Scientists are to outline dramatic evidence that global warming threatens the planet in a new and unexpected way – by triggering earthquakes, tsunamis, avalanches and volcanic eruptions.

Reports by international groups of researchers – to be presented at a London conference next week – will show that climate change, caused by rising outputs of carbon dioxide from vehicles, factories and power stations, will not only affect the atmosphere and the sea but will alter the geology of the Earth.

Melting glaciers will set off avalanches, floods and mud flows in the Alps and other mountain ranges; torrential rainfall in the UK is likely to cause widespread erosion; while disappearing Greenland and Antarctic ice sheets threaten to let loose underwater landslides, triggering tsunamis that could even strike the seas around Britain.

At the same time the disappearance of ice caps will change the pressures acting on the Earth's crust and set off volcanic eruptions across the globe. Life on Earth faces a warm future – and a fiery one.

Now, there is little doubt that there is a possible link between climate change and geophysical hazards, and that this is a topic that requires study. But to present the topic in this way is ridiculous given our current state of knowledge. Some elements of the quote above are probably untrue (melting glaciers will set of avalanches for example), and some of the remainder is speculative at best (e.g. widespread erosion in the UK, underwater landslides from the loss of ice sheets). Much of the rest has sensationalised climate impacts by presenting end member (i.e. large but unlikely) events as having a far great likelihood than is the reality - e.g. the UK being affected by tsunamis generated by underwater landslides caused by Arctic melting. This is possible, but is very, very unlikely, and there is little if any evidence that such events have occurred in the past.

But, unfortunately it gets worse. Bill McGuire, the Director of the Benfield Hazards Research Centre at UCL, is quoted as saying the following:

'"Not only are the oceans and atmosphere conspiring against us, bringing baking temperatures, more powerful storms and floods, but the crust beneath our feet seems likely to join in too," said Professor Bill McGuire, director of the Benfield Hazard Research Centre, at University College London (UCL)."Maybe the Earth is trying to tell us something,"'.

Now I like and admire Bill, I consider to be a friend, and I think that he has done a lot of good stuff. But this type of quote is really unhelpful. In my view there is no place for scientists to state things sthat the the oceans and atmosphere are "conspiring against us" - they are responding to the forcing that we are causing. And what can one say about a scientist stating that "Maybe the Earth is trying to tell us something"?

The remainder of the article is rather more measured, with some not unreasonable quotes from some good scientists. However, the damage is done in the first part of the article, and of course in the headline.

Take a look at the comments on the Guardian web page. Unsurprisingly, the denialist community has jumped on this to undermine the research that is being undertaken on climate change. This is a great shame - anthropogenic climate change is a huge issue based on good science. Unfortunately, articles like this, based on speculation and exaggeration, are really unhelpful to those trying to do good science and to persuade society of the importance of this issue. If there is one thing that I have learnt in the last couple of years is that as scientists we need to be measured and realistic about what we write and say. The organisers of this conference would be wise to remember this.

The Cikangkareng village landslide, Indonesia

As I reported a couple of days ago, the Mw=7.0 earthquake in Indonesia on Wednesday triggered a substantive landslide in the village of Cikangkareng in West Java. This landslide buried ten houses, a mosque and an amusement (video game) arcade with the loss of about 57 lives. AP have today released images of the landslide that are quite interesting. In particular this one:

Why is this interesting? Well, first lets note that we should ignore the red colour on the face of the scarp - this is a mantle of tropical soil that have come down from the crown of the slide (you can see the red soil at the very top of the landslide - this is of course typical of a tropical area). More important is the structure behind the mantle of soil debris. Here it is clear that the rocks are horizontally-bedded (or at least nearly so). Such a large failure in horizontally-bedded rocks is certainly not unprecedented, but is slightly surprising. The debris is very coarse-grained and has travelled quite a long way, which is also interesting.

Often, failures like this are associated with some process that has caused undercutting of the toe - for example wave erosion. Clearly there are no waves here - I wonder if there had been any activity to quarry stone from the slope, perhaps as a building material?

I am reminded of the Manshiet Nasser landslide in Cairo a year ago:

In that case the key cause was probably quarrying at the foot of the slope.

The geological structure of the Hsiaolin slide

Thanks to reader Chingying Tsou, who has answered my request for information about the geological structure of the Hsiaolin landslide. He has provided a link to the website of the Sino-Geotechnics Research and Development Foundation, which provides the key information. The page is in Chinese, but the diagrams are really helpful, as is the Google translation.



So here is a topographic map of the landslide site, with the major faults and of course the landslide itself marked on:

You will note two cross-section lines on the map, one of which (A-A') runs down the axis of the landslide. This cross-section is reproduced below:


It is clear from this that the landslide is a dipslope failure - i.e. the slide has occurred on beds that are orientated parallel to the slope, and thus facilitate failure. The cross-section indicates that the rocks are a mixture of sandstone and shale. This can often cause problems as the shale is weak, impermeable and prone to weathering, whereas the sandstone is often stronger but allows the accumulation of water (i.e. pore pressure generation). The presence of the fault is an additional factor - it may well be that the movement on the fault has caused the beds to be disrupted and thus weakened. It should also be noted that this cross-section is probably only indicative. It would not surprise me to find that the river has actually eroded out the lower portions of these beds, then filled in the spaces with the terrace deposits upon which the village was built, further weakening the slope.

The Hsiaolin landslide slope before failure

In an earlier post I highlighted a satellite image of the Hsiaolin landslide site. I have trimmed this a little below:


This image is rather helpful as it starts to allow the site of the landslide before failure to be examined using Google Earth, which has good quality imagery of this area. This is, as close as I can get it, the same slope prior to failure:

Click on the image for a better view in a new window.

There are a couple of things to note here. First, the slide ran out straight across the village, removing all trace as the earlier photographs showed. Second, the rivers clearly underwent huge amounts of flooding.

A perspective view of the site is a little more helpful:


I have annotated the image below to locate the approximate boundaries of the landslide, using the satellite image above plus the photographs of the site that are now available (see this post)



You may need to click on the image to be able to see the boundaries properly. These boundaries are at the moment very much indicative, but they give the general idea. The landslide is intriguing because the slope was not showing obvious signs of instability as far as I can see, bar a depression in the head scarp area the could be a tension crack? The river has clearly undercut the toe of the slope, which could have been a factor? It would be interesting to know more about the underlying bedrock, and in particular the dip direction. Can anyone provide any more information?

Comments welcome.