The Walnut Grove 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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85° on Nov. 11, 2002, the hottest reading for this week of the year since 1883. Next is 84° in 1931.
Walnut Grove’s center stands about 770 ft above sea level. Within three miles the land runs from 610 ft to 830 ft, a difference of 220 ft: rolling country.
Under the town center the state geologic map shows Eutaw Formation (sand), from the Cretaceous, 66 to 145 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 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.
Sand. Age: Cretaceous, 66 to 145 million years old. About 9 mi of the line.
Chert. Age: Carboniferous, 324 to 359 million years old. About 5 mi of the line.
Gravel. Age: Cretaceous, 66 to 145 million years old. About 4 mi of the line.
Chert. Age: Carboniferous, 324 to 359 million years old. About 3 mi of the line.
Fine-detrital, coarse-detrital. Age: Quaternary, less than 2.6 million years old. About 1 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 Walnut Grove reaches the Gulf of America by way of Holland Creek, Horse Creek, the Tennessee, the Ohio and the Mississippi: about 1,220 river miles.
Lake on the way: Pickwick 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 Walnut Grove; river miles along the main stem, rounded.
Walnut Grove has a humid subtropical climate. Summer afternoons average 91° in July; winter nights fall to about 30° in January. About 59 inches of rain fall in a normal year.
On November 14 Walnut Grove normally reaches 64° and falls to 40°. The record high is 82°, in 1931; the record low 15°, in 2019. The most rain on this date, 2.80 in, fell in 1989.
Normals 1991–2020 and records since 1883 at Savannah 6 SW, 17 miles west-northwest, 320 ft lower. NOAA, through RCC-ACIS.
