Falls Lake Geology - An Interactive Guide

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Falls Lake was created by the U.S. Army Corps of Engineers to help control flooding along the Neuse River.  Construction of the dam began in 1978 and the lake was completed in 1981.  Falls Dam is located north of Raleigh, NC at the small community of Falls in Wake County.  The lake is named after the Falls of the Neuse, a location of rock water falls and cascades, now submerged by the lake.  The dam impounds water approximately 28 miles upstream to the confluences of the Eno, Flat and Little River in Durham County.

This 28 mile course of the lake exposes various rocks types along the shore that help tell a significant portion (over a half a billions years) of the geologic history of North Carolina.   
Falls Lake general geology
Generalized geologic map of the Falls Lake area, North Carolina (modified from NCGS, 1985).

The Eno, Flat and Little Rivers converge to form the Neuse River northeast of Durham in a portion of the North Carolina Piedmont sometimes referred to as the Triassic lowlands.  The Triassic lowlands are underlain by approximately 220 million year old sedimentary rocks within an area known geologically as the Triassic basin.   Here the distances from one side of the lake to the other can be over a half a mile across and the lake is shallow (rarely reaching depths over 8 feet except for in the submerged Neuse River channel).   The lake maintains this character all the way to where Highway 50 crosses the lake.  Near this location, the lake crosses a major geologic boundary (an ancient fault) and enters another portion of the Piedmont sometimes referred to as the Piedmont upland.  The Piedmont upland is underlain by approximately 300 to 630 million year old igneous and metamorphic rocks.  In the Piedmont upland, the lake is narrow- rarely reaching widths more than 1000 feet across and can be deep in places (over 30 feet deep within the submerged Neuse River channel).  The shore of the lake is also steeper compared to the lake west of Highway 50. 

In some respects, Falls Lake is “two” lakes.  “One” lake is characterized by wide and open shores with relatively shallow depths.  The “other” lake is characterized by a narrow lake bed, steep shore and relatively deep areas.  Falls Lake is not two lakes but one lake that flows over two drastically different rock types.  It is the character of the rock types that controls the nature of the topography and therefore the nature of the lake.

About this website:

This website was created as a general guide to the geology of the Falls Lake area utilizing data collected by the North Carolina Geological Survey (NCGS) staff and other past workers.

Contact Phil Bradley with the NCGS for additional geologic information: pbradley@ncdenr.gov