Tar pit

According to the Tenth Doctor, tar pits were responsible for humans knowing about extinct animals. Beasts of earlier epochs would become trapped in the tar and die, but the tar would preserve the animal's skeleton more or less intact. Some of the most famous tar pits were the La Brea tar pits in Los Angeles, which the Doctor said had preserved thousands of animals. (PROSE: The Last Dodo)
There was a tar pit located in London in 1993 on an alternate Earth. When the Seventh Doctor's TARDIS fell through into that universe it became trapped in a tar pit. It remained there until just prior to the Doctor initiating a time ram with his alternate self's TARDIS, at which point it was removed by the Fortean Flicker. (PROSE: Blood Heat)
Tar pits could also be found on the surface of Messaline. (TV: The Doctor's Daughter)
Circa 35,000 BCE, the Doctor's TARDIS landed on the site of the future Los Angeles in a tar pit. (COMIC: The Doctor and the Nurse) When the Tenth Doctor and Martha Jones visited the city in the 1950s, the Doctor suggested visiting the La Brea Tar Pits among other sites. (COMIC: Quiet on the Set)
Category:Natural features