Therefore, is an important, but little visible, contributor to Long Island's topography. However, because of the glacial cover, exposed Cretaceous sediments are limited to a few scattered localities on present day Long Island. The figure below shows the areas above sea level as they might appear if they had not been covered by the younger glacial deposits. The top surface of the Cretaceous reaches elevations above sea level over an extensive area of northern Nassau and northwestern Is over 2,000 feet thick under Fire Island, but it thins towards the north shore and the western end of the Island to pinch out under Long Island's Sound, Resting on the bedrock and extending under nearly all of Long Island is a massive wedge of Cretaceous sediments (sands, clays and gravels). The bedrock slopes down to the south and east beneath the rest of Long Island and therefore does not form any significant landforms here. Surface exposures of the bedrock are widespread in Manhattan and the Bronx but are limited on Long Island to small outcrops in northwestern Queens. The foundation upon which Long Island rests, and the deposition of sands and clays on this bedrock 70 million years ago, during the late Cretaceous period. Pre-glacial geologic events in the Long Island include the formation of the ancient (over 400 million year old) metamorphic bedrock that forms
Whether they occurred before, during or after the advance of a continental glacier onto the Island. On Long Island these processes can be grouped into three categories - pre-glacial, Each natural land feature originated through the action of some The surface of Long Island is made up of many varied and interesting landforms.
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