William's Ridge is underlain by a 12-15 km thick crust, which is significantly thicker than the adjacent Labuan Basin crust, but similar to that of the Kerguelen Plateau. It rises to only 500 metres below the sea level and appears to consist of two blocks separated by a narrow fault-bounded valley. Williams Ridge has not been drilled and the stratigraphy and nature of the basement are unknown.

A spectacular dipping reflector sequence has been intersected on Line 179-07 on the western flank of the ridge. It is 50 km long and about 1.2 sec thick, with the top part of the sequence faulted in the west. Massive lava flows normally have a strong magnetic signature, however dipping sequence on the William's Ridge has no magnetic anomaly. This may indicate the presence of significant amounts of sediment or sedimentary origin of the sequence.