 The Gap of Dunloe was formed 25,000 years ago during Ireland's last ice age as a result of a "glacial breach" where a glacier in the "Black Valley", part of the Templenoe Icecap, estimated to be over 500 metres deep, broke through the "Head of the Gap" and moved northwards carving out a U-shaped valley.The pass runs north-south between the Old Red Sandstone mountain ranges of the MacGillycuddy's Reeks (to the west) and the Purple Mountain Group (to the east).The north-south road through The Gap as the area is also known, goes from "Kate Kearney's Cottage" in the north, to the highest point at the "Head of the Gap" at , and down to "Lord Brandon's Cottage" in the "Black Valley" in the south.