The Mornington landscape is immensely beautiful. The Baulk Face Range dominates the central part of the sanctuary. This massive mesa is roughly 30 km in diameter and rises about 150 m above the adjacent terrain. Fitzroy Bluff is a taller but smaller (about 10 km long) mesa standing majestically in the southern portion of the sanctuary, nestled amongst the spectacular King Leopold Ranges to the south, Sir John Range to the East and Lady Forrest Range to the west.
Several permanent rivers (including the Adcock, Traine, and Hann Rivers) flow through the vast savanna plains and drain into the Fitzroy River. These waterways sometimes dissect the terrain for several kilometres to form spectacular vertical-walled gorges such as Dimond Gorge and Sir John Gorge.
The dominant habitat of Mornington is tropical savanna. The grasslands are lightly sprinkled with stands of low eucalypts, Kimberley Bauhinia, Acacias, Boabs and native Kapok. On the sandstone ranges and uplands, the savanna grades into very open woodlands with a spinifex understorey. The margins of creeks and rivers are lined with thick riparian vegetation, including pandanus palms, plum trees and river red gums. Pockets of Livistona palms and rainforest thrive in the gullies of the ranges and mesas.
Mornington has an exceptionally interesting geological history. The Kimberley Basin, is a Proterozoic sedimentary basin ranging in age from over 2 billion to 1.7 billion years (that is, prior to the development of life). It received vast amounts of aquatic and terrestrial sediment and volcanic deposits during that period, but has not been inundated by the sea since then. Today, it is a plateau with a dissected surface developed over mostly flat-lying rocks. However, the southern margin of the property is intensely folded where the Kimberley Basin abuts the King Leopold Range (and the associated Sir John and Lady Forrest Ranges).