The Lewiston plate. Relief from Copernicus GLO-30; rivers and lakes from USGS NHD; watersheds from the USGS Watershed Boundary Dataset; roads and city limits from Census TIGER 2024.
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Lewiston’s center stands about 1,230 ft above sea level. Within three miles the land runs from 1,200 ft to 1,390 ft, a difference of 190 ft: gently rolling country. The highest named summit within 15 miles is Mount Tom, about 1,510 ft, 12 miles southeast.
The section below crosses 3 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 35×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Shale. Age: Carboniferous, 324 to 359 million years old. About 22 mi of the line.
Shale. Age: Late Devonian, 359 to 384 million years old. About 2 mi of the line.
Black-shale. Age: Devonian to Carboniferous, 324 to 422 million years old. About 0.8 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale.
Heights from Copernicus GLO-90 (a surface model: it includes buildings and tree canopy); summits from USGS GNIS; rivers from USGS NHDPlus HR; rock from the USGS State Geologic Map Compilation.
A raindrop that lands in Lewiston reaches Lake Huron by way of Middle Branch Big Creek, East Branch Big Creek, the North Branch Au Sable and the Au Sable: about 110 river miles. From there it moves on through the Great Lakes, over Niagara Falls and down the St. Lawrence to the Atlantic.
95 miles of the trip are on the Au Sable.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Lewiston; river miles along the main stem, rounded.
