The Boulder 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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68° on Nov. 13, 1995, the hottest reading for this week of the year since 1954. Next is 67° in 1989.
Boulder’s center stands about 7,030 ft above sea level. Within three miles the land runs from 6,270 ft to 7,580 ft, a difference of 1,310 ft: steep hill country. The highest named summit within 15 miles is Bowns Point, about 10,970 ft, 10 miles north-northeast.
Under the town center the state geologic map shows Bluff Ss, Summerville Fm, Curtis Fm, Entrada Ss, and Carmel Formation (sandstone), from the Middle Jurassic to Late Jurassic, 145 to 175 million 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 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.
Arenite. Age: Early Jurassic, 175 to 202 million years old. About 6 mi of the line.
Sandstone. Age: Middle Jurassic to Late Jurassic, 145 to 175 million years old. About 6 mi of the line.
Unconsolidated. Age: Pleistocene, less than 2.6 million years old. About 6 mi of the line.
Coarse-detrital. Age: Quaternary, less than 2.6 million years old. About 3 mi of the line.
Unconsolidated. Age: Quaternary, less than 2.6 million years old. About 2 mi of the line.
Felsic-volcanic. Age: Late Oligocene to Middle Miocene, 12 to 28 million 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 Boulder reaches the Gulf of California by way of Boulder Creek, the Escalante and the Colorado: about 960 river miles.
Lakes on the way: Lake Mead, Lake Powell, Lake Mohave and Lake Havasu.
290 miles of the trip are on the Colorado.
Seldom reaches the sea. Dams and canals now take nearly all of the Colorado before its old delta in Mexico.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Boulder; river miles along the main stem, rounded.
Boulder has a cold semi-arid climate. Summer afternoons average 84° in July; winter nights fall to about 21° in January. A normal year brings about 52 inches of snow; with the rain, that comes to about 12 inches of water.
On November 14 Boulder normally reaches 50° and falls to 30°. The record high is 65°, in 1999; the record low 9°, in 1964. The most rain on this date, 0.48 in, fell in 1955.
Normals 1991–2020 and records since 1954 at Boulder, here, 380 ft lower. NOAA, through RCC-ACIS.
