The Black Hawk 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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−16° on Nov. 13, 2014, the coldest reading for this week of the year since 1893. Next is −6° in 1951.
Black Hawk’s center stands about 8,130 ft above sea level. Within three miles the land runs from 7,850 ft to 9,620 ft, a difference of 1,770 ft: steep hill country. The highest named summit within 15 miles is Rogers Peak, about 13,330 ft, 14 miles south-southwest.
Under the town center the state geologic map shows Biotitic gneiss, schist, and migmatite (biotite-gneiss, schist, migmatite), from the Paleoproterozoic, 1.6 to 2.5 billion 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 3×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Biotite-gneiss, schist, migmatite. Age: Paleoproterozoic, 1.6 to 2.5 billion years old. About 14 mi of the line.
Gneiss. Age: Paleoproterozoic, 1.6 to 2.5 billion years old. About 10 mi of the line.
Granite. Age: Paleoproterozoic, 1.6 to 2.5 billion years old. About 0.6 mi of the line.
Granitic, dioritic. Age: Late Cretaceous to Middle Eocene, 40 to 72 million years old. About 0.3 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 Black Hawk reaches the Gulf of America by way of North Clear Creek, Clear Creek, the South Platte, the Platte, the Missouri and the Mississippi: about 2,430 river miles.
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 Black Hawk; river miles along the main stem, rounded.
Black Hawk has a warm-summer humid continental climate. Summer afternoons average 77° in July; winter nights fall to about 15° in December. A normal year brings about 106 inches of snow; with the rain, that comes to about 18 inches of water.
On November 14 Black Hawk normally reaches 45° and falls to 22°. The record high is 68°, in 1999; the record low −2°, in 2014. The most rain on this date, 0.41 in, fell in 1978.
Normals 1991–2020 and records since 1893 at Georgetown, 13 miles west-southwest, 390 ft higher. NOAA, through RCC-ACIS.
