The World’s Largest Caves, by Richard Walters
The speaker started with some spectacular images of the UK’s longest cave system, across the borders of Cumbria, Yorkshire and Lancashire – hence the Three Counties cave.
He explained his interest in locating, and measuring by laser, the largest cave caverns in the world. The overall largest is the Miao Room in China, where it took seven days underground to record its size.
He explained the technology which enables 3D images of the inside walls of the chambers to be produced. These images can then be rotated and linked to surface topography. After much computer manipulation, animations can show the entrance into the caves, views of the enormous stalagmite formations, and an idea of the extent of the cave, which cavers themselves cannot see at the time. Using simple diagrams, the formation of large caverns was explained.
Water meeting from different channels underground becomes aggressive again, and can dissolve more limestone. Stress on the arch structure of the cavern roof was explained as keeping these enormous cavern roofs standing, while unstressed rocks collapses into loose blocks. The fate of all large cavern chambers is to collapse, especially when chambers have an open roof. Yorkshire’s Hull Pot is believed to be a collapsed cavern.
3D images of the underground workings of Nenthead mines were shown, and finally the 3D laser plotted the inside of the meeting room, together with all CGS members. It was a truly memorable illustrated talk, taking us underground without having to make any effort.
A write-up of the event on 10th February 2016 by Sylvia Woodhead.
