The Boulder Canyon 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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Mostly sunny; warmer
Mostly sunny
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Mostly sunny; cooler
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Chance of showers
78° on Nov. 12, 1999, the hottest reading for this week of the year since 1902. Next is 77° in 1990.
Boulder Canyon’s center stands about 4,040 ft above sea level. Within three miles the land runs from 3,580 ft to 5,200 ft, a difference of 1,620 ft: steep hill country. The highest named summit within 15 miles is Terry Peak, about 7,040 ft, 12 miles west-southwest.
The section below crosses 20 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.
Coarse-detrital, fine-detrital. Age: Quaternary, less than 2.6 million years old. About 4 mi of the line.
Claystone, siltstone, sandstone. Age: Eocene to Oligocene, 23 to 56 million years old. About 3 mi of the line.
Shale. Age: Late Cretaceous, 66 to 100 million years old. About 2 mi of the line.
Quartzite, schist. Age: Paleoproterozoic, 1.6 to 2.5 billion years old. About 2 mi of the line.
Limestone, dolostone. Age: Late Devonian to Early Mississippian, 347 to 384 million years old. About 2 mi of the line.
Hypabyssal-latite, hypabyssal-andesite, hypabyssal-quartz-latite. Age: Paleocene to Eocene, 34 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. 14 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 Boulder Canyon reaches the Gulf of America by way of Bear Butte Creek, the Belle Fourche, the Cheyenne, the Missouri and the Mississippi: about 2,520 river miles.
Lakes on the way: Lake Oahe, Lake Sharpe, Lake Francis Case and Lewis and Clark Lake.
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 Boulder Canyon; river miles along the main stem, rounded.
Boulder Canyon has a hot-summer humid continental climate. Summer afternoons average 86° in July; winter nights fall to about 15° in January. A normal year brings about 48 inches of snow; with the rain, that comes to about 21 inches of water.
On November 14 Boulder Canyon normally reaches 48° and falls to 25°. The record high is 77°, in 1990; the record low −20°, in 1959. The most rain on this date, 0.59 in, fell in 1956.
Normals 1991–2020 and records since 1902 at Fort Meade, 6 miles east, 730 ft lower. NOAA, through RCC-ACIS.
