Scadbury is situated on rocks dating from the Lower Eocene period, about 50-60 million years ago, when much of north Kent and southern Essex was submerged under a shallow sea or lagoon.
The higher parts of Scadbury towards Chislehurst Common lie on the Blackheath Beds which consist of sand and pebbles. This is a poor soil and tends to be left as woodland.
The Blackheath Beds give way to the silts and clays of the Woolwich Beds. A number of springs rise along the juncture of the Blackheath and Woolwich Beds.
This is the source of the water supply in the wells which provided water for the moated manor house.
The more open areas, now used for grazing and hay, are on soils derived from the Thanet Sands. This is a better soil for agriculture and a large part of Scadbury was covered with commercial fruit orchards for much of the 20th century.