Wednesday 2 September 2015

Walking Back In Time

A wonderful afternoon on Sunday's rAmble where David Webster led us on a geological path through time. Down at Kilnaughton Bay, we learnt about the underlying natural processes which have shaped Islay as we see it today, whilst identifying tell-tale rock formations that illustrate the past. 

The walk began with Jura Quartzite, where the rock layers noticeably dip in a South East direction - meaning we were walking in the direction of younger days ahead! Here a rare form of kyanite mineral can be found. This Quartzite is what makes up the Paps of Jura.
Jura Quartzite layered rock
Moving on, as well as examples of compressed sedimentary rock squashed to form slate, we were introduced to a new rock type - conglomerate - seen down by the lighthouse, identifiable by the small pebbles embedded in the layers. 

David Webster pointing out the curvature in the conglomerate rock layers

Pebble remains of raised beach

Further along, groupings of isolated pebbles around 20m higher than today's coastline tells the story of the past where sea levels were higher, perhaps due to glacier melt water from the last ice age. These pebbles represent raised beaches bordering the sea cliffs which now sit inland from the shoreline. Similarly, large sea stack rock columns along our path would have once been surrounded by sea.

Fault rock alignment 

The last rock feature lead us down on to the Singing Sands. Here we were able to see an alignment of rock along the sand and out to sea, representing the underlying fault line. The dyke rock feature stands out on the sands and can often be identified by its honeycomb stacking structure and rough sandpaper texture.

 An incoming rain shower towards the end was in fact exactly what we needed to allow the group to get their feet scuffing and hear the Singing Sands "sing" - or squeak to be more accurate! The erosion of the Quartzite rock creates these sands and along with the combination of shell deposits and added moisture, you can enjoy a tuneful stroll on the beach.

Our group making tracks down at the Singing Sands

Thanks to David Webster for this wonderful walk and helping us get our heads around all the geological terms and timescales! A fascinating walk discovering Islay's ancient landscape. - Lorna 

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