The risen seabed was that abyssal plain that also buried most of H.P. Lovecraft's sunken primordial city of R'lyeh.
R'lyeh is a fictional lost city that was first documented in the H. P. Lovecraft short story "The Call of Cthulhu", first published in Weird Tales in February 1928. R'lyeh is a sunken city in the South Pacific and the prison of the entity called Cthulhu.