The Steep Gullies are the most difficult terrain at The Basin. Extreme Terrain is defined by the Colorado Ski Safety Act as:
"Extreme Terrain" means any place within the ski area boundary that contains cliffs with a minimum twenty-foot rise over a fifteen-foot run, and slopes with a minimum fifty-degree average pitch over a one-hundred-foot run.
The Steep Gullies definitely meet this definition. Extreme Terrain is not about moguls or trees or rocks. It is about steepness and cliffs.
