The Marble Mountain Wilderness lies within the Klamath Mountains west of Fort Jones, California. This particular section b/w Black Marble Mountain & Marble Mountain contains a vast region of marble karst, w/ many channels & sinks of sculpted rock in solution leading down to vertical pits & cave entrances. There are at least 150 known cave entrances within the karst, the largest is Bigfoot Cave w/ about 12.4 miles of known passages & a depth of 1,205 feet, which is more than Oregon Caves to the north. This is overlooking two vertical pits, at least 50 feet down into a cave system. Along this channel going uphill were several more pits of considerable drop w/ the sound of meltwater within. The geology of the Klamath Mountains is among the most bizarre & intriguing in North America, nearby atop the marble & w/in are schist deposits & the adjacent higher peaks w/in the Boulder Peak region is comprised of red peridotite. To the south, one can see the snowy Trinity Alps, of Sierra Batholith origin.