Source: TW
The Javanese book of kings – pustaka rAja pUrva has never been translated fully but a little snippet translated from the oldest manuscript talks of a cataclysmic event separating Java from Sumatra in the 338th year of the shaka calendar:
“There was a furious shaking of the earth, total darkness, thunder and lightning.
Then came forth a furious gale together with torrential rain, and a deadly storm darkened the world.
A great flood then came from Mount Batuwara and flowed eastwards to Mount Kamula.
When the waters subsided it could be seen that the island of Java had been split in two, thus creating the island of Sumatra.”
There are some versions that are even more vivid, but people think these might have been “contaminated” by recent accounts of Krakatoa filtering into later manuscripts. Unfortunately, this issue remains unresolved.
Of course, Java and Sumatra likely did not separate that recently but the record in the pustaka rAja pUrva might be an old memory of a volcanic cataclysm followed by a tsunami. It is reminiscent of the Javan explosion recorded in the Calcutta stone: