Complex sentence: The Craven Gap is sometimes called the Aire Gap, but to do so necessitates including the Aire Fault; that runs from the south end of the South Craven Fault: from Gargrave towards Leeds.
Split into simpler sentences: The Craven Gap is sometimes called the Aire Gap, but to do so necessitates including the Aire Fault. This fault runs from near Gargrave, at the south end of the South Craven Fault, towards Leeds.