The Last Glacial Maximum (LGM) refers to that period in earth's history when the glaciers were at their thickest and the sea levels at their lowest.
An artist's impression of ice age Earth at glacial maximum. Based on: Crowley, T. "Ice age terrestrial carbon changes revisited" Ice age - Wikipedia, the free encyclopedia
The map shows the probable extent of land and water at the time of the last Glacial Maximum some years BP when the sea level was probably more than 110 meters lower than it is today.
north atlantic last glacial maximum