The petrified jungle, also called the petrified forest, was the remains of a forest on Skaro, in which all vegetation had been turned to stone, presumably by the use of neutron bombs in the neutronic war (or, alternatively, in the Thousand Year War).
History
The TARDIS materialised in the jungle when it first arrived on Skaro. The First Doctor, Susan, Ian and Barbara found the body of a magnedon there. A party of Thals led by Temmosus made their camp in the jungle during their quest to save their people. (TV: The Daleks) According to one account, which took place some time earlier, Susan landed the TARDIS in the jungle in an attempt to visit Venus. (COMIC: The Message of Mystery)
When the Doctor used the fast return switch in an attempt to return Ian and Barbara to their native time, it gave out halfway through and brought the TARDIS back to the petrified jungle, 50 cycles after their last visit. Exploring, the group noted that life was beginning to return to the area. (AUDIO: Return to Skaro)
At some point, presumably in the 41st century, an area of the jungle was recovered from Skaro by humans and taken to Station 7 for the Space Security Service to research. A Slyther, Varga plant and the same magnedon the First Doctor came across was included. The Eleventh Doctor and Amy Pond arrived in the jungle area shortly before a Dalek force attacked while searching for a human experiment on Dalek nature which disgusted them. The jungle was destroyed along with the station when the Daleks concluded the experiment was not on board. (COMIC: The Only Good Dalek)
When Anya Kingdom, the Tenth Doctor and Davros were brought to Kembel, the latter two compared the damage that the Time Destructor had done to the planet to the petrified jungle. (AUDIO: The Dalek Defence)