Soil to new conditions. Whether these are slow or rapid changes depends on climate, topography and biological activity. The physical properties of soils, in order of decreasing importance for ecosystem services such as crop production, are texture, structure, bulk density, porosity, consistency, temperature, colour and resistivity. Soil texture is determined by the relative proportion of the three kinds of soil mineral particles, called soil separates: sand, silt, and clay. At the next larger scale, soil structures called peds or more commonly "soil aggregates" are created from the soil separates when iron oxides, carbonates, clay, silica and humus, coat particles and cause
Parramatta Sand Body Conservation Area and Military Barracks Site and slightly mottled with depth. The upper parts of the soil profile are usually heavily mixed, especially by cicada larvae. In places the sand is cut by deposits of mottled or gleyed clay that were probably deposited in swamps or waterholes on the terrace surface. The reasonably defined levee, 50 to 100 centimetres high, along the terrace edge between Charles and Alfred Streets, comprises cleaner and very slightly coarser sand than the sand found around the margins of the levee. The profile of the sand suggests that the main body of sand is of late Pleistocene age and recent thermoluminesence