In geology, a forebulge is created when an large static weight (such an
ice sheet) causes the
subsidence of a continent into the
mantle. The resulting mantle deformation results in an upward displacement in the areas surrounding the ice load. This disturbance can spread, in a
ripple effect, around the earth and affect even tropical regions that see no ice.
Sites of former forebulges (from the
last glacial maximum), include
Antarctica, the
Netherlands and other areas adjacent the
North Sea and the
eastern coast of the U.S., have experienced prolonged relative sea level rise during the
Quaternary as the
forebulge subsided. The ripple effect from the multiple
collapsing forebulges can last thousands of years resulting in varying
relative sea levels and
isostatic rebound leaving shorelines of the past hundreds of meters above present
sea level.