The Allison Gap 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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13° on Nov. 15, 2014, the coldest reading for this week of the year since 1894. Next is 13° in 2019.
Allison Gap’s center stands about 1,910 ft above sea level. Within three miles the land runs from 1,700 ft to 4,090 ft, a difference of 2,390 ft: mountain country. The highest named summit within 15 miles is Beartown Mountain, about 4,710 ft, 7 miles west-northwest.
The section below crosses 11 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 7×. 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: Ordovician, 445 to 487 million years old. About 7 mi of the line.
Shale. Age: Ordovician, 445 to 487 million years old. About 4 mi of the line.
Age: Ordovician to Silurian, 422 to 487 million years old. About 3 mi of the line.
Dolostone, limestone. Age: Cambrian to Ordovician, 445 to 542 million years old. About 2 mi of the line.
Shale, sandstone. Age: Devonian, 359 to 422 million years old. About 2 mi of the line.
Shale, sandstone. Age: Devonian, 359 to 422 million years old. About 2 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 5 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 Allison Gap reaches the Gulf of America by way of Robertson Branch, the North Fork Holston, the Holston, the Tennessee, the Ohio and the Mississippi: about 1,880 river miles.
Lakes on the way: Guntersville Lake, White Lake (historical), Pickwick Lake and Cummings Lake.
970 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Allison Gap; river miles along the main stem, rounded.
Allison Gap has a humid subtropical climate. Summer afternoons average 84° in July; winter nights fall to about 23° in January. A normal year brings about 10 inches of snow; with the rain, that comes to about 48 inches of water.
On November 14 Allison Gap normally reaches 58° and falls to 31°. The record high is 77°, in 1958; the record low 14°, in 2019. The most rain on this date, 0.61 in, fell in 1929.
Normals 1991–2020 and records since 1894 at Saltville 1 N, here, 180 ft lower. NOAA, through RCC-ACIS.
