Balcones Escarpment - A series of geologic faults running through West Austin and extending to the North and South through central Texas.
Barton Springs - Artesian springs located in central Austin.
Caliche - A hard soil layer rich in calcium carbonate leached from the soil above that is found throughout the city.
Edwards Aquifer - An artesian aquifer lying under the city's southwest quadrant and extending south past San Antonio.
Limestone - The city of Austin lies in what was a huge shallow sea during the cretaceous period and a thick layer of limestone underlies most of the city.
Pilot Knob - A cretaceous era volcano formed underwater and located in southeast Austin.