The Hornbrook 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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13° on Nov. 12, 2020, the coldest reading for this week of the year since 1948. Next is 16° in 2014.
Hornbrook’s center stands about 2,180 ft above sea level. Within three miles the land runs from 2,090 ft to 4,100 ft, a difference of 2,010 ft: mountain country. The highest named summit within 15 miles is Mount Ashland, about 7,480 ft, 15 miles northwest.
Under the town center the state geologic map shows Upper Cretaceous marine rocks, unit 2 (Klamath Mountains) (sandstone, mudstone), from the Early Cretaceous to Late Cretaceous, 66 to 113 million years old.
The section below crosses 7 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 5×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Andesite, basalt. Age: Late Oligocene to Pleistocene, 2 to 24 million years old. About 11 mi of the line.
Mafic-volcanic, greenstone. Age: Paleozoic to Mesozoic, 66 to 542 million years old. About 4 mi of the line.
Melange. Age: Devonian to Jurassic, 145 to 422 million years old. About 4 mi of the line.
Sandstone, mudstone. Age: Early Cretaceous to Late Cretaceous, 66 to 113 million years old. About 3 mi of the line.
Diorite. Age: Jurassic to Early Cretaceous, 100 to 202 million years old. About 1 mi of the line.
Peridotite, serpentinite. Age: Neoproterozoic to Early Jurassic, 175 to 1,000 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. 1 smaller unit 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 Hornbrook reaches the Pacific Ocean by way of Cottonwood Creek and the Klamath: about 180 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Hornbrook; river miles along the main stem, rounded.
Hornbrook has a hot-summer Mediterranean climate. Summer afternoons average 93° in July; winter nights fall to about 26° in January. About 12 inches of rain fall in a normal year.
On November 14 Hornbrook normally reaches 55° and falls to 30°. The record high is 65°, in 2019; the record low 20°, in 2018. The most rain on this date, 0.38 in, fell in 1948.
Normals 1991–2020 and records since 1948 at Montague Siskiyou Airport, 10 miles south-southeast, 460 ft higher. NOAA, through RCC-ACIS.
