Say the lost continent of Lemuria was real, and was home to an ancient sophisticated civilization that like the Atlanteans, dabbled in high technologies and forbidden magicks. Due to their fatal curiosity, the continent experienced a cataclysm that caused most of the continent to sink apart from three continental fragment islands.
Realistically, how could the native people survive a cataclysm strong enough to sink most of their continent into an ocean? Is there any way? I also imagine modern explorers finding the lost three islands, and finding them absolutely littered with ruins of the Lemurian civilization? Is it feasible that stonework architecture would have survived the cataclysm too?
I prefer realistic answers, but supernatural answers are welcome if there are no other explanations.