Ice cap

The ice caps were the permanent coverings of ice over a planet's poles.

In the time of the Vikings, the Vostok went into hiding under the ice caps. (COMIC: The Return of the Vostok)

In the 1970s, Broton planned to get rid of Earth's ice caps to make the planet more like the Zygons' homeworld. (TV: Terror of the Zygons)

In 2008, Connie Winter noted to Thomas Brewster that the news was full of bad things like the ice caps melting. (AUDIO: A Perfect World)

In 2009, the Spaerons melted Earth's ice caps, flooding the planet. They restored the ice caps to their natural state after the Tenth Doctor offered to move them to Kerun Za instead. (COMIC: The Aquarius Condition)

In 2765, the Zygons attempted to melt the ice caps and flood the world, but were stopped by INITEC's Vigilant laser defence satellite system. (PROSE: Original Sin)

In 5000, the ice caps began to advance due to the Second Ice Age. (TV: The Ice Warriors)

At some point, the Daleks used a neutronic power unit in an attempt to melt Antarctica's ice cap and flood the world, but were stopped by the Anti-Dalek Force. (COMIC: Flood!!!)

In the Earth of Pete's World, the ice caps were melting by 2010. This was a result of global warming exacerbated by travel through the Void into N-Space. (TV: Doomsday)

In an alternate timeline, the SunTrap had caused the ice cap at the North Pole to melt. (PROSE: Prisoners of the Sun)

In 2017, the probe Valkyrie probed the ice caps of Mars and discovered the message "God save the Queen." (TV: Empress of Mars)

The planet Throssa had an acid ice cap. (PROSE: Original Sin)