The mud springs were 'discovered' in 1974, although they must have been known of for much longer. They are a rare geological phenomenon. This image is from within the small copse containing the springs and shows a mud spring. The length of wood visible above my size 10 boot has been pushed into the mud to a depth of about 1.5 metres. There was negligible resistance to the insertion of the branch and the mud pool is probably many metres deep. Lots of stuff on the web.