A Natural Resource Management Guide for the County of Morris A ...

Geologic History of Morris County
Introduction
This inventory of Morris County's environmental features begins with geology because, indeed, it describes
the substrate upon which subsequent layers of soil, water, vegetation, wildlife habitat and microclimates have
evolved. An understanding of geologic history contributes to an understanding of human settlement patterns,
transportation routes, and the location of certain economic activities. Current application of this
understanding can be made in rectifying and preventing the problems associated with these assorted land uses,
e.g., depleted aquifers, mine shaft-related cave-ins, sinkholes, and radon hot spots.
Ancient History
The processes that produced the geologic structures underlying Morris County have been operating for over
one billion years. The landscape that we see is the result of cyclical mountain building, erosion, rock relocation
into valleys, metamorphosis, and recycled rock being thrust up into mountains again.
Primitive rivers carved channels in the rock, forming deep valleys, only to have their direction reversed in
response to the changing tilt of the land mass or the blockage of old drainage ways by erosional deposition.
Seas have advanced across the land surface, and then retreated. The climate has changed from tropical to
arctic and back to temperate as the landmass itself has drifted nearer then farther from the equator. Glaciers
have descended from the north, covered more than half the county, and then melted back; their passage
radically reshaping the landscape and trapping the groundwater that serves us today.
Geologic history is traditionally divided according to the duration of time needed to form recognizable rock
units. The longest such division is commonly known as an Era. Eras are then subdivided into Periods.
Periods may be further subdivided into Epochs. Table 1, on the following page, provides an overview of this
chronology. As you continue to read, refer to the corresponding formations depicted on the bedrock geology
map Plate 1. The variations within this geologic base have contributed to the environmental diversity specific
to the county.
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Geologic History of Morris County