Friday, 22 July 2011

Looking at rocks.

My dad worked at Shap Granite and I grew up in Tebay so I was always going to have an interest in geology.  From my house I could see the Silurian mud stones ( I believe these are now called the Windermere supergroup , Shap Granite, Carboniferous Limestone and Borrowdale volcanics.

It was time to look at rocks again.  I left the car at the Blencathra Centre and followed the path around above the Glenderaterra Beck.  The rocks being Skiddaw mudstones laid down in an ocean trench 480 million years ago.  This trip was to look at the Skiddaw Granite which is exposed in Sinen Gill. This is part of a batholith of granite underlying the Lake District, it intruded into the Skiddaw mudstones 400 million years ago.  The heat metamorphosed the mudstones and as you get closer to Sinen Gill the mudstones gradually change.

The first gill is about half a mile from the granite and the mudstones have developed white crystals of chiastolite.  As you walk further the mudstones get harder and become hornfels often with dark spots of cordierite.  Eventually in Sinen Gill you come across a 2m high waterfall of granite blocks.

The granite is pale in colour and is exposed in the beck bottom.

On the surrounding slopes are some very hard examples of the folded hornfels.

Not an expert so apologies for any inaccuracies.


Anonymous said...

This is an interesting piece, Greg. I'll keep my eyes open for the folded hornfels next time I'm in the area. With such complex geology in the Lakes there's always something new to see.
Alen McF

Greg said...

Thanks Alen. Loved your video by the way. I'm sure it reminded me of someone.... Bean's Boots springs to mind a program I vaguely remember from the past.

Alan R said...

Thanks Greg. Loads of interesting points to watch out for there.
Thanks for sharing.