[aurizon]

at 10,000 feet in a thermal area the rock is very hot. Hot rock is ductile and holes will gradually close. Some deep hard rock mines in Northern Ontario encounter this problem where mine working gradually close under extreme pressure over time. The closure can be instant = rock-burst = a local micro-quake. Often there is lateral shear as well. The deepest gold mines in Witwatersrand in South Africa are over 160 degrees in places and workers wear vented/cooled suits. They also have refrigerated cold rooms they can jump into to get cool and get back to another work session.