Thursday, 8 October 2015

The story of a rock

This I think would make a great animation movie.

Look at this rock we found in a core we opened this morning. 

Let me tell you its story:
We think this is a gneiss, a metamporphic rock that is formed when you take an igneous rock like a granite, or a sedimentary rock like a sandstone and you put it under a lo-o-t of pressure and relatively high temperature. So the life of this rock started when magma rose to the surface of the earth and crystallised to form a granite. This rock was then eroded and turned to sediment, which was deposited somewhere maybe on a beach. This area then got drowned by the sea and what used to be a beach is now buried several km deep under other sediments at the bottom of an ocean. These buried rocks were subjected to great pressures and relatively high temperatures is they are buried very deep. Then tectonic movements pushed this area and this rock and uplifted it high - so much that the rock ended up being part of a mountain. Temperatures dropped significantly and ice age started and the mountain got covered by glaciers, which moved over the rocks and grounded them and picked up pieces of it, locked them in the ice and transported them 100’s of km across a continent to the ice shelf margin where it meets the sea. The glacier started breaking down. Icebergs, containing the rocks the glaciers had eroded and locked inside the ice, broke off and one of them travelled over the St Pierre slope and while travelling, it started melting, and as it was melting any rocks inside it sank to the seafloor. That part of the seafloor then became part of a submarine landslide and the rock got trapped inside the landslide deposit together with the sediments on which it had settled and it stayed there for a very very very long time, until a bunch of scientists from Germany, Canada, Ireland and UK dropped a 12cm diameter gravity corer and brought the rock inside the landslide deposit up to the surface again…

Tell me now that geology isn’t fascinating and awe-inspiring!

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