Westland lies astride one of the most dramatic geological features on the Earth: the Alpine Fault, which separates two global scale plates of crustal rock. To the east, the Pacific Plate stretches to North and South America. To the west the Australian Plate includes all of Australia to the Indian Ocean. These two plates are moving against each other at the Alpine Fault. The east side is being pushed up to make the Southern Alps, with the Alpine Fault at the base of the mountains from Milford Sound to Blenheim. The west side is moving northwards, and has carried rocks nearly 500 km from Otago to Nelson.