The Parklands are located within the geological unit of Sydney known as the Botany Sands. 

The Botany Sands overlay the northern edge of the Botany Basin and are composed of a complex of Aeolian sand dunes of the Holocene era, of variable thickness, with an underlying layer of inter-bedded clays, peats and sands. This material resulted in a natural landform of rounded sand dunes and expanses of gentle slopes with local depressions and exposed water tables (ponds and marshes).  Before alienation of parkland, the north-eastern corner of the original park revealed extensive outcrops of Hawkesbury sandstone, some still evident in Centennial Park.

The underlying Quaternary Hawkesbury sandstone emerges to form a ridge to the north and east, and its more elevated and broken topography helps to define the spatial character of the Botany Sands system.  It acts as a wall to the sand.  Some of the Aeolian sand from the Botany system has been deposited on the tip of the ridge and slopes of the sandstone outcrop giving a visually deceptive rounded form in contrast to its more typical blocky, stepped form. 

Natural drainage seeps through the blocky jointed stone and collects in the natural aquifer, the Botany Sands, as well as in the intermittent surface streams and ponds which were formalised into the Parklands drainage system. The residential precinct of Lang Road, Martin Road, Cook Road, Robertson Road straddles a further north/south trending spur of Hawkesbury sandstone.

The original soil type for the Centennial Parklands is a white crystalline wind-blown sand of the Holocene era, overlying Hawkesbury Sandstone which outcrops at the northern edge of Centennial Park before dipping to depths of between eight to two hundred and fifty meters south towards Botany Bay. 

Bands and lenses of Waverley Coffee Rock, a finely textured soft impermeable mudstone occur at numerous locations in the lower lying sections of the Parklands. The resultant podsolised soil profiles are azonal, acidic and with only weakly differentiated or non existent horizon development. Decaying vegetation provides humus in a thin upper A horizon with staining and discoloration of the prevalent white sand. Nutrient status is low, the absence of clay causing low cation exchange capacity, and particles in the fine to very fine range contributing to the drainage characteristics of the parklands.

Substantial modifications were made to the landscape in the late 1800s and in most areas a pattern of cut and fill has been used to create the current landforms. Original sands are typically identified by their whiteness, having been leached of nutrients.

The remnant sand dunes include Mount Steel (although highly modified on its northern aspect), the York Road area extending into Centennial Park, the Bird Sanctuary, Parade Ground Pine Grove, Randwick Gates Pine Grove, the Kensington Pond dune, and the Queens Park Road boundary. Some of these areas support elements of the remnant vegetation type known as Eastern Suburbs Banksia Scrub.