The Allentown 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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Allentown’s center stands about 440 ft above sea level. Within three miles the land runs from 330 ft to 490 ft, a difference of 160 ft: gently rolling country.
Under the town center the state geologic map shows Neogene undifferentiated (sandstone, claystone), from the Tertiary Neogene, 2.6 to 23 million years old.
The section below crosses 4 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 62×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sandstone, claystone. Age: Tertiary Neogene, 2.6 to 23 million years old. About 11 mi of the line.
Sand. Age: Eocene, 34 to 56 million years old. About 6 mi of the line.
Clay. Age: Eocene, 34 to 56 million years old. About 5 mi of the line.
Limestone. Age: Oligocene, 23 to 34 million years old. About 3 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 Allentown reaches the Atlantic Ocean by way of Little Rocky Creek, Rocky Creek, Turkey Creek, the Oconee and the Altamaha: about 220 river miles.
130 miles of the trip are on the Altamaha.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Allentown; river miles along the main stem, rounded.
