The Big Sandy 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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77° on Nov. 12, 1999, the hottest reading for this week of the year since 1921. Next is 73° in 2025.
Big Sandy’s center stands about 2,700 ft above sea level. Within three miles the land runs from 2,670 ft to 2,940 ft, a difference of 270 ft: rolling country. The highest named summit within 15 miles is Centennial Mountain, about 5,770 ft, 13 miles east.
Under the town center the state geologic map shows Claggett Formation (shale), from the Late Cretaceous, 72 to 84 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 14×. 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: Late Cretaceous, 72 to 84 million years old. About 11 mi of the line.
Sandstone, shale. Age: Late Cretaceous, 72 to 84 million years old. About 7 mi of the line.
Sandstone, shale, siltstone. Age: Paleocene to Middle Paleocene, 59 to 66 million years old. About 4 mi of the line.
Mafic-volcanic. Age: Tertiary, 2.6 to 66 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.
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 Big Sandy reaches the Gulf of America by way of Little Sandy Creek, the Missouri and the Mississippi: about 3,190 river miles.
Lakes on the way: Lake Oahe, Lake Sakakawea, Lake Fort Peck and Lake Sharpe.
1,170 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Big Sandy; river miles along the main stem, rounded.
Big Sandy has a cold semi-arid climate. Summer afternoons average 86° in July; winter nights fall to about 10° in January. About 13 inches of rain fall in a normal year.
On November 14 Big Sandy normally reaches 44° and falls to 22°. The record high is 72°, in 1999; the record low −22°, in 2014. The most rain on this date, 0.39 in, fell in 1927.
Normals 1991–2020 and records since 1921 at Big Sandy, 4 miles southeast. NOAA, through RCC-ACIS.
