The Blackgum 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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Blackgum’s center stands about 910 ft above sea level. Within three miles the land runs from 540 ft to 1,080 ft, a difference of 540 ft: hilly country. The highest named summit within 15 miles is Beaver Mountain, about 1,630 ft, 11 miles east-northeast.
Under the town center the state geologic map shows Atoka Formation (shale, sandstone), from the Carboniferous, 299 to 324 million years old.
The section below crosses 5 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 17×. 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, sandstone. Age: Carboniferous, 299 to 324 million years old. About 17 mi of the line.
Fine-detrital. Age: Holocene, less than 12,000 years old. About 2 mi of the line.
Limestone, shale, sandstone. Age: Carboniferous, 299 to 324 million years old. About 2 mi of the line.
Limestone, shale. Age: Carboniferous, 324 to 359 million years old. About 1 mi of the line.
Chert, limestone. Age: Carboniferous, 324 to 359 million years old. About 0.9 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 Blackgum reaches the Gulf of America by way of Tenkiller Ferry Lake, the Illinois, the Arkansas and the Mississippi: about 990 river miles.
Lakes on the way: Murray Lake, Tenkiller Ferry Lake and Ozark Lake.
600 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Blackgum; river miles along the main stem, rounded.
