What is fracking?

The Northern Territory government has lifted a ban on hydraulic fracturing or fracking, but what is the controversial mining process.

WHAT IS FRACKING:

* Creation and enhancement of fractures in rock using a gas or fluid injected at high pressure.

* Increases the ability of water and gas to flow through a coal seam, enhancing extraction of gas.

* Accesses gas deposits that can't be recovered using conventional techniques.

* Controversial mining process with exploration companies believing it can be employed safely.

* Opposition from environmental and indigenous groups because of potential for subsurface and groundwater contamination.

* Concerns it can also lead to increased seismic activity, though any events are usually small.

Source: Australian Government. Department of the Environment.