The Clarksville 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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Clarksville’s center stands about 440 ft above sea level. Within three miles the land runs from 370 ft to 500 ft, a difference of 130 ft: gently rolling country.
Under the town center the state geologic map shows Annona Chalk, from the Late Cretaceous, 66 to 72 million years old.
The section below crosses 9 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 64×. 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. Age: Late Cretaceous, 66 to 100 million years old. About 5 mi of the line.
Fine-detrital, coarse-detrital. Age: Holocene, less than 12,000 years old. About 4 mi of the line.
Clay. Age: Late Cretaceous, 66 to 72 million years old. About 3 mi of the line.
Marlstone, claystone. Age: Late Cretaceous, 66 to 100 million years old. About 3 mi of the line.
Chalk. Age: Late Cretaceous, 66 to 72 million years old. About 3 mi of the line.
Sand. Age: Pleistocene to Holocene, less than 2.6 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. 3 smaller units along the line are not listed.
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 Clarksville reaches the Gulf of America by way of Delaware Creek, Langford Creek, Cuthand Creek, the Sulphur, the Red River, the Atchafalaya and the Lower Atchafalaya: about 620 river miles.
Lake on the way: Wright Patman Lake.
320 miles of the trip are on the Red River.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Clarksville; river miles along the main stem, rounded.
