The Colby 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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−6° on Nov. 17, 1959, the coldest reading for this week of the year since 1946. Next is −5° in 1986.
Colby’s center stands about 1,350 ft above sea level. Within three miles the land runs from 1,290 ft to 1,430 ft, a difference of 140 ft: gently rolling country.
Under the town center the state geologic map shows Gneiss and amphibolite (gneiss, amphibolite), from the Paleoproterozoic, 1.6 to 2.5 billion years old.
The section below crosses 6 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 64×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sandstone. Age: Cambrian, 487 to 542 million years old. About 11 mi of the line.
Granodiorite, tonalite. Age: Paleoproterozoic, 1.8 to 1.8 billion years old. About 5 mi of the line.
Granite. Age: Paleoproterozoic, 1.8 to 1.9 billion years old. About 4 mi of the line.
Gneiss, amphibolite. Age: Paleoproterozoic, 1.6 to 2.5 billion years old. About 3 mi of the line.
Basalt, basaltic-andesite. Age: Paleoproterozoic, 1.6 to 2.5 billion years old. About 1 mi of the line.
Rhyolite, dacite. Age: Paleoproterozoic, 1.8 to 1.8 billion 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 Colby reaches the Gulf of America by way of Elm Brook, Dill Creek, the Big Eau Pleine, the Wisconsin and the Mississippi: about 1,900 river miles.
Lakes on the way: Petenwell Lake, Lake Wisconsin, Lake Du Bay and Wisconsin River Flowage 4964.
1,610 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Colby; river miles along the main stem, rounded.
Colby has a warm-summer humid continental climate. Summer afternoons average 79° in July; winter nights fall to about 2° in January. A normal year brings about 51 inches of snow; with the rain, that comes to about 34 inches of water.
On November 14 Colby normally reaches 40° and falls to 24°. The record high is 66°, in 1999; the record low −4°, in 1986. The most rain on this date, 0.48 in, fell in 1951.
Normals 1991–2020 and records since 1946 at Owen 1 E, 12 miles west-northwest, 110 ft lower. NOAA, through RCC-ACIS.
