By way of a contrast with WoGE 222, which was a fine and detailed view of a desert, I've produced a wide view of a reasonably rainy place.
Find the spot on GoogleEarth (latitude/longitude) and describe the geology.
I really don't think this will be hard, so the Schott rule is definitely in place, if you've never won before, now is your chance. If you've won before, wait an hour for each solution before you can post.
53°12'N 1°58'W
ReplyDeleteWe are looking at volcanic flows on limestone in the Peak District UK .
About 340 million years ago, the area which is now the Peak District was covered by a warm, clear, shallow sea.
This is now the rock which is known as Carboniferous Limestone and this rock lies under the whole of the Peak District (see quarry).
From about 300 million years ago, large rivers from adjacent continents to the North began to drain into the sea and deposit silt, which was gradually compressed to form rocks.
These layers eventually covered all the Limestone.
Later islands of land formed and became richly vegetated, with trees and huge ferns. However, in this period the land was constantly sinking and rivers were changing their course, so areas of land often would subside and become covered in water again. This laid down a series of layers of alternating shale and vegetable deposits which are now known as the Coal Measures.
Later on the land went up and down and the top layers of rock eroded away. During this period the rock (especially the limestone) often cracked under the pressures and molten rock (magma) was forced into the fissures.
In these cracks overheated water circulated and formed together with the magma lots of minable ore deposits as lead, copper, baryt.
The result was the many mineral veins or rakes which are to be found in the limestone areas and which have been mined for lead and other minerals since at least Roman times.
Please correct me, if didn't sum up the complicated history correct enough.
Finding this spot was very easy for a newbie like me. I identified Your helpful comment with the "reasonably" rainy place immediately as typical britisch understatement and looked in a place where I'm always soaked with rain while traveling on the wrong side of the road. The Buxton limestone quarry looked exactly the same as the quarries in my area, so it was an easy pick.
ReplyDeleteLocation 53.187 N 2.000 W
ReplyDeleteWe're in the Peak District of England's Derbyshire, and the town of Buxton is just to the north of this image.
The Peak district is mainly Carboniferous rocks and the area around Buxton is limestone, sandstone and shale. The River Wye which is at the top right of the image is has formed "Poole's Cavern" in the limestone. In Buxton, there's "St. Ann's Well" which, according to wikipedia is geothermal spring fed and commercially bottled.
There also appear to be terraces (brown features in the center) and active quarries (white features to the right.
Buxton is home to Poole's Cavern, an extensive limestone cavern open to the public, and St Ann's Well, fed by the geothermal spring bottled and sold internationally by Buxton Mineral Water Company."
We have a winner!
ReplyDeleteCongratulations Felix, please post your entry here when you are ready.
I hadn't thought the rain reference was such a big clue (it's not *that* rainy here ;->) but the GetMapping reference on the image is a big clue, I think they only cover the UK.
Good summaries of the geology from you and Anne. Some further remarks from me.
The limestone is in the right third of the map, with the rest being Millstone Grit and Coal Measures. In the early Carbonferous the Peak District was a shallow area surrounded by deeper water, so the limestones are paritcularly pure (and so valuable).
Anne mentions the terraces in the centre. It is a kind of trap topography with thick resistant gritty sandstone layers forming small cliffs and flat areas in between on the softer shales. The small cliffs are know locally as Edges and are usually covered in rock climbers.
The pattern of the ridges is boat-shaped due to a syncline (Goyt syncline), with the trace going N-S. Not quite the Makran, but quite nice I think.
Felix mentioned the alternating layers. When I was a lad the theory was as he says, the cause was thought to be delta switching or something similar. Now however the pattern of the stratigraphy is know to be glacio-eustatic in origin. That is, regular major sea-level change due to Milankovitch cycles affecting polar ice-caps and changing the volume of ice over time.
Finally, the coal measures are thin in this area, with only minor "bell-pit" mines. However the same rocks in Yorkshire and Lancashire have massive deposits which arguably are one reason for the Industrial Revolution to start in northern England.
Simon, thank you for your explanation of the geology.
ReplyDeleteWOGE #224 ist up at: http://woge-felix.blogspot.com/