Geology means "study of the Earth." Perhaps most fundamental to this endeavor is the concept of "geologic time." As our understanding of the great antiquity of the Earth developed, names were assigned to segments of time defined in units ranging from thousands of years (in the relatively recent geologic past to historic times), to many millions or billions of years (in the distant geologic past). Geologists use the geologic time scale to define the ages of rocks, the processes that formed them, or the age of the fossils they may contain.The geologic time scale (below) highlights selected "events" relating to the New York City region.

Figure 5. Geologic time scale for NYC region.

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