A General Sinking of Sea-Level in Recent Time

Abstract

Among the causes of world-wide or "eustatic" shifts of sea-level are: appropriate crustal movements whereby the volume of the ocean basin delta-building and volcanic extravasation on the sea-floor, the displacement of sea-water not being compensated by crustal subsidence; volcanic addition of new water to the ocean; subtraction of water which becomes chemically bound during the alteration of rocks; glaciation on land, loweriig sea-level by the abstraction of water from the ocean; de- glaciation on land, raising sea-level; changes in the earth's center of gravity and in her speed of rotation. Numerous as these possibilities are, eustatic shifts at definite times and in definite amounts have not often been postu- lated by geologists. The proof of such a shift, either positive or negative, is not easy. The present note records some field facts suggesting the probability of a sinking of general sea-level to the extent of nearly 20 feet, during the Human period.