Krakatoa

From TARDIS Index File, the free Doctor Who reference.

Krakatoa is a volcanic island in the south Pacific Ocean. It erupted in 1883.

Sometime prior to his third incarnation, the Doctor witnessed the eruption; during this event, he also heard Primords for the first time. (DW: Inferno, NA: All-Consuming Fire, NA: The English Way of Death)

That same day, a sketch of Ninth Doctor washed up on a beach on Sumatra. It eventually found its way into Clive Finch's collection of artifacts related to the Doctor. (DW: Rose)

Tenth Doctor and Rose Tyler visited Indonesia, encountered the alien Chalderan. They managed to escape in the TARDIS just as the volcano erupted. (DWAM: Under the Volcano)

The Krakatoa eruption also caused one Xylok to be freed. This Xylok became Mr Smith many years later. (SJA: The Lost Boy)