Location: Sand Point, Sand Bay, Keystoke nr Weston super Mare
Date: 15 / 03 / 16
Present: Jo Lathwood / Professor Kathy Cashman / Paul Blakemore
Weather: Mild, sunny patches with a brisk wind
Aim: To find basaltic lava pillows
Introduction:
Sand Point is a Sites of Special Scientific Interest (SSSI) and is owned by the National Trust. Various people at Bristol University mentioned it might be a good starting point to find some volcanic rock as the University takes students on a field trips there. I contacted the National Trust to see if they would give me permission to take some samples from the site. Within a week I received an email stating it would be acceptable to take a small sample of loose material but not to chisel into the lava pillows. Delighted, we headed out to Sand Point.
Outcome:
The geology of Sand Point is quite mixed and as we arrived the realisation of looking for a particular rock amongst 3 miles of coastline seemed rather daunting. The tide was going out and slowly revealing more of the cliff face. To my ignorant observation I first thought most of formations were basalt because as far as the eye could see there was black rock but sadly that was not the case. The majority of black rock was in fact black limestone which would be of no use to me. After a nice stroll and a lunch break we found the pillows – thanks to Kathy’s understanding of the landscape and an old geology guide of the area.
The pillows were smooth dark grey boulders with calcite veins running though them. Behind them was a larger structure which pushed its way out of the cliff side. Ever hopeful we spent a bit of time looking for loose pieces that could be basalt but frustrating to no avail. The basalt was very much in the pillow and only a chisel would relinquish a sample. I picked up some pieces of volcanic tuff – a rock made from the ash of a volcano that is pretty soft and brittle and we headed home. I will test test the tuff but my gut reaction is that it wouldn’t work as well as basalt so now I must find another source.
