Kindly go through this Quora Answer -
This answer presents a perspective of what could have actually been the Jambudweep back then. I don’t know whether the analysis is right or wrong but it’s certainly plausible to go through all of it.
Given that the Earth has been through quite a lot of asteroid hits in the past as well. This creates a question in my mind whether the Earth was a lot bigger in the 4th Era and some asteroid hit has made it what it is today along with the tectonic plate shifting?