The Blue Mountains and Great Dividing Range were formed about 50 million years ago when the area was uplifted. More recently, volcanic flows covered large areas of the mountains in basalt. These have largely worn away, leaving only occasional outcrops on the high peaks.
As the cracks formed in the rock strata, water slowly eroded away the sandstone to create canyons of spectacular beauty.
Over 2000 kilometres of rock face has been left behind, making it a rock climbing mecca for both local and international climbers.