Sinkholes
At 2pm on Friday 13th December 19 geology group members met in Ruthin library to listen to Dr. Frank Nicholson give his presentation on 'Sinkholes'. The £2 fee included a Christmas raffle ticket and festive refreshments.
Sinkhole, cenote, sink, swallet, swallow hole and doline are the various names used when referring to sinkholes. They are found world wide and vary in size from very small to enormous. Some appearing as small depressions in the ground, others wide, gaping, deep holes.They can cause damage to human life and property and can appear in the centre of towns, the middle of a motor way or under a house, swallowing up what ever was above before it collapsed. These collapses can occur very quickly or gradually depending on the cause of the collapse.
Sinkholes are either formed naturally or man-made. Naturally formed ones are caused by slightly acid rain water constantly draining through the ground eroding/dissolving away the permeable rock such as limestone or chalk to such an extent that it can no longer support the ground above hence the collapse.
Man- made sinkholes are usually the result of water or sewage escaping from burst pipes beneath the ground washing away the surrounding ground leaving a cavity which cannot support the land, road, house or whatever is above it and causing a collapse.
I will ask Frank for a pdf of the presentation which explains with diagrams how various sinkholes form and many photos of sinks throughout the world.
Thank you to members who brought raffle prizes and food, thanks to Karen, Beryl and kitchen helper for the day Mike for their services with the refreshments.
Merry Christmas To The Whole Geology Group.
Isabel
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