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Sunday, August 15, 2010

Geological treasures - history in the landscape.

No change - or if any, for the worse. Foggy, cold drizzle, enough breeze to add a chill factor and drive the drizzle into your face and elsewhere on the trek to the drum and with the little things that matter exposed.

So - 13 of us, temporarily marooned in a tent complex in a geological treasure chest. The camp is close to the remains of a 350 million year old coral reef with fossils from before fish had teeth. Channels, canyons and lakebeds everywhere, from the ice age and the great melt - the valleys were formed by moving ice and water as the huge ice sheet melted. This site was under about 2 miles of ice which formed lakes as it melted and then rivers that carried deposited silt on to flood plains and down to the sea. There are huge rocks scattered around that were carried on the surface of the ice and dropped through as it melted - called, not surprisingly, drop-stones. Berrimilla's Rock is a piece of the original coral reef that broke off an exposed ridge perhaps 10,000 years ago and rolled down to its present spot.

And the camp is beside the Haughton Crater, formed about 39 million years ago by the impact of a meteorite estimated to have been half a mile across. The meteorite vaporised as it impacted, bringing up the geological strata from a mile below the surface and melting it in the explosion so that as it cooled it became breccia - a complex mix of once molten fragments and cooling vapour that is a a grey and rough rock - until you cut it and polish the surface to reveal the complexity of the structure of the rock. The crater was formed in a few seconds as the molten fragments spread outwards at a kilometre a second. Pascal is, among other things, a geologist and he is taking samples this year for analysis to try to establish the composition of the meteorite impactor.