The Basin 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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71° on Nov. 12, 1999, the hottest reading for this week of the year since 1880. Next is 67° in 1990.
Basin’s center stands about 5,350 ft above sea level. Within three miles the land runs from 5,250 ft to 7,400 ft, a difference of 2,150 ft: mountain country. The highest named summit within 15 miles is Haystack Mountain, about 8,780 ft, 9 miles south-southwest.
Under the town center the state geologic map shows Granitic rock, 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 6×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Granitic. Age: Cretaceous, 66 to 145 million years old. About 13 mi of the line.
Andesite, latite. Age: Late Cretaceous, 72 to 84 million years old. About 4 mi of the line.
Gravel, sand, silt. Age: Pleistocene to Holocene, less than 1.8 million years old. About 4 mi of the line.
Quartz-latite. Age: Early Eocene to Middle Eocene, 41 to 56 million years old. About 2 mi of the line.
Age: Late Miocene to Holocene, less than 7.2 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 Basin reaches the Gulf of America by way of the Boulder, Jefferson Slough, the Jefferson, the Missouri and the Mississippi: about 3,570 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 Basin; river miles along the main stem, rounded.
Basin has a cold semi-arid climate. Summer afternoons average 83° in July; winter nights fall to about 11° in December. About 11 inches of rain fall in a normal year.
On November 14 Basin normally reaches 43° and falls to 19°. The record high is 66°, in 1999; the record low −18°, in 1959. The most rain on this date, 0.50 in, fell in 1989.
Normals 1991–2020 and records since 1880 at Boulder, 8 miles east-southeast, 450 ft lower. NOAA, through RCC-ACIS.
