The One Billion Year Gap

Although this was a free day, with no geology input planned, Mr Flum and I decided that, as the tide was favourable, we should try to see the One Billion Year Gap at its most impressive, that is, from the seaward side. This had not been possible on the day of our guided visit.

Our reference book, co-written by our guide, David Webster, explains a similar photo thus:
"The shear zone is about 3m wide and comprises very sheared rocks which have been eroded into a gulley. On the right are the 1,800 million year old (Ma) gneisses of the Rhinns Complex and on the left are bedded quartzites of the lower part of the Colonsay Group, which are probably about 750 Ma. The shear zone thus represents an age gap of about 1 billion years".

The extra shows the view towards the sea from deep within the cleft: in both cases Mr Flum is included for scale.

So ends our brilliant U3A trip, we depart at different times according to the vagaries of the ferries.