Friday, 17 July 2009

Surveyors

A quiet day today. I went for a walk this morning to clear my head, get some air, and to remind myself why I chose to live here. I managed to avoid the thunder showers that have been plaguing this part of Europe today, but when I got back to my place, I discovered a couple of geological surveyors in my field, doing what you might expect....surveying. I could tell, from the long, white pole one of them was carrying like a tightrope balancing pole, and the fact that he wasn't on a tightrope.




The nearby village of Saulges was bathed in sunlight against a dark cloud











I introduced myself as the owner of the field and asked the what they were up to, and they explained that they had been asked by the archaeologists digging the prehistoric caves nearby to see if they could find any more caves, and they were looking at all the fields they could in the area. So once permissions were sought and given, they carried on.


This isn't a very good picture, because it's of a dull computer screen in daylight, but it shows clearly, the "anomaly" they found; the big red/green area at the top left of the screen. It is an area of reduced ground resistivity, and they thought it might represent a collapsed cave roof that has filled with soil. So they came back in the afternoon to do a more sophisticated test.












This pic shows the tape measure they laid out on the ground through the centre of the anomaly, and the cable they connected up to probes hammered into the ground along its length. This will give them an accurate measure of soil resistivity to a much greater depth than the computer screen image above.












Here are the surveyors with their cunning measuring device They promised to drop round tomorrow to tell me what they discover.













A little bit of brooding, thundery atmosphere :)













They returned as promised, and the image below shows the results they got. I have tilted it so that you get an idea of the slope of the land. The blue area is soil (low resistivity) and you can see this layer of soil on top on the rocks (red). It looks like water has eroded a basin in the rocks, and the brown area leading away from the bottom left hand edge of the blue is perhaps where the water soaks away.


They did another measurement today, at 90 degrees to this one, through the middle of the brown area, about where the yellow splodge is. This to see if the water is soaking away through fissures or perhaps some form of tunnel. They said they'd send me the picture they get and if they do, I'll post it on the blog.

3 comments:

ReedBunting said...

Cool, geophysicists! You'll have Tony Robinson round there with a JCB before you know it!! :)

dyanna said...

I like your blog.I'm waiting for your new posts.

Cogitator said...

Hello Dyanna, and welcome to my blog. I hope it continues to be interesting for you.

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