The specific consequences of sea level rise for the Alexander Archipelago of southeastern Alaska were complex.

During the glacial maximum, the entire region had been covered by the Cordilleran Ice Sheet — a vast mass of glacial ice that extended from the coast to the interior and that, at its maximum, covered virtually all of the landscape now occupied by the archipelago and its surrounding waters.

The islands were not islands during the glacial maximum; they were submerged under ice, their limestone and granite and metamorphic rock ground and scraped by the moving glacier.

As the ice sheet melted, beginning approximately 17,000 to 15,000 years ago, the islands emerged from beneath the ice — a process called deglaciation that proceeded from south to north as the climate warmed.