1 November 2010
A sinkhole in Germany, a landslide in Italy and the forecast path of Hurricane Tomas (which has already caused landslides in St Lucia)
Posted by Dave Petley
Today is one of those days in which there is a great deal going on. Three interesting stories are:
Thanks to a host of people for bringing the development last night of a sinkhole in the town of Schmalkalden in central Germany to my attention. These feature has been caught in a spectacular set of images, of which the one to the left is a good example, available in a gallery on the Der Spiegel website.
The sinkhole, which reportedly is 30 metres in diameter and 20 metres deep, opened up at 3 am (local time) this morning. No-one has been injured or killed, although the owner of the property may have some trouble getting his/her cars out of the garage for a while. Note the cracks in the road near to the hole by the way.
Most sinkholes of this type result from one of two different processes. Some are the result of solution of soluble rocks, such as limestone or salt. The rest are usually the result of the collapse of shallow excavations, usually old mines but sometimes metro train workings or suchlike. In this case, this article (editor’s note: link expired) appears to point to a potential cause:
“In the middle ages, artisans and craftsmen benefited from the iron ore deposits in the mountains of the Thüringer forests…The wealth of the iron ore deposits, the mining thereof and the working of the extracted iron into handmade goods helped to establish the town and its economic future and carried it through well into the next century and beyond…Mining and production continued even after the Second World War when Schmalkalden belonged to the Deutsche Democratic Republic (DDR).”
2. A landslide in Italy
Meanwhile, in Italy last night a landslide occurred in the town of Massa in Tuscany, killing a two year old boy and his mother. There are a couple of photos here, if you excuse the appalling headline to the article (the Daily Mail makes me feel embarrassed to be British).
Across the Atlantic, Hurricane Tomas continues its westward movement. Tropical Storm Risk is continuing to forecast that it will veer northwards in a few days time (see image), producing a track that will see it passing directly over the earthquake-affected areas of Haiti. The caveat here is of course the inaccuracy of track forecasts, especially where a dramatic change in direction is included. Fortunately, it is now considered less likely that it will intensify as much as feared, but even a category 1 storm has the potential to have very major consequences in this area. There is now a real need to start planning for this event; fortunately the media are now reporting that such a response has been initiated. Let’s hope that this time there is a plan that will allow assistance to be quickly delivered should the worst case scenario occur.
Details are slowly emerging of the impact that Hurricane Tomas has had on St Lucia. Caribbean World News reports: “Death and destruction – these are the words being used to describe the mayhem caused by Hurricane Tomas on the island of St. Lucia … Many communities are severely damaged and the village of Soufriere has been declared a disaster zone … Hundreds of houses have been destroyed and several roads and bridges are impassable. The island`s banana industry has been totally wiped out and there have been massive landslides in the southern part of the island … Prime Minister Stephenson King says the extent of the damage will be over a hundred million dollars … King says that the island will need regional and international assistance.”
In the Schmalkalden area there the iron ores are bound to the Zechstein. It is supposed that during the Tertiary fault-bound thermal waters led to the ore formation by replacing the Ca with Fe. However, Dolomites and limestones are still present close to the surface in some places and might be subejct to solution…
See also:
Wagenbreth, O. & Steiner, W. 1990. Geologische Streifzüge. Dt. Verl. für Grundstoff ind., Leipzig, pp 104ff, 116, 118. (in German, not available online)
Some possible further information’s to the sinkhole of Schmalkalden: According to a TV news report yesterday evening (02.11.2010) where the minister of the environment of Thuringia figured, the area of the village was not subjected to any mining activity in the past, it seems to (re)confirm that the sinkhole is the result of a natural collapse* after the dissolution of the underlying evaporate-bearing sediments of (I think) the Buntsandstein/Zechstein –formation (widely distributed in Thuringia).
* however it remains the question if the water needed for the dissolution did not eventually came from s broken pipe – not an unusual trigger for such a phenomenon. In the published fotos there are some pipes, however no water visible (?)
There is a nice series of 31 photographs of “sinkholes, craters and collapsed roads around the world” on the Daily Telegraph (London) website:
http://www.telegraph.co.uk/earth/earthpicturegalleries/7818648/In-pictures-sinkholes-craters-and-collapsed-roads-around-the-world.html
The iron ores in the Schmalkalden area developed during the Tertiary, when hydrothermal water followed fault lines that control the present day shape of the Thuringian Forest. Ca was replaced with Fe in the Zechstein. Solution is most likely the cause in this case. There have been a number of similar cases in Thuringia during the last months, e.g., Tiefenort, Nordhausen, Kyffhäuser etc.
See also:
Wagenbreth, O & Steiner, W. 1990. Geologische Streifzüge. Dt. Verl. für Grundstoffind., Leipzig
(in German and online not available, sorry)
Oh, sorry for double posting, I wasn’t able to see the comments and thought I had a technical problem…
Dave, I’m using Firefox to view this page and the text in the main column is cut off along its RHS, with the pale blue RH column apparently overlapping it. Thought you ought to know!
Cheers – John