The term is used to describe a geological division, a travel route, or a location that is an entry into the Aire river valley.
Geologically the Aire Gap lies between the Craven Fault and the limestone uplands of the Yorkshire Dales to the north and the Forest of Bowland and the millstone grit moors of the South Pennines.
[2] The term Aire Gap is used in both Ribblesdale and Pendle to denote a hypsograph (watershed) between those rivers and Airedale.
The treeless moorland gives no shelter and modern Pennine transport can find it a formidable barrier when roads are blocked by snow for several days.
The nearest alternative pass is Stainmore Gap (Eden-Tees)[10] to the north that climbs to 409 m (1,342 ft) and its climate is classed as sub-arctic in places.