The Alleghany 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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80° on Nov. 14, 1995, the hottest reading for this week of the year since 1948. Next is 77° in 1949.
Alleghany’s center stands about 4,120 ft above sea level. Within three miles the land runs from 2,900 ft to 5,660 ft, a difference of 2,760 ft: mountain country. The highest named summit within 15 miles is Sierra Buttes, about 8,430 ft, 14 miles northeast.
Under the town center the state geologic map shows Undivided pre-Cenozoic metavolcanic rocks, unit 2 (undivided) (mafic-volcanic, greenstone), from the Paleozoic to Mesozoic, 66 to 542 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 4×. 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. Age: Late Oligocene to Pleistocene, 2 to 24 million years old. About 7 mi of the line.
Argillite, phyllite. Age: Permian to Jurassic, 145 to 299 million years old. About 6 mi of the line.
Argillite, quartzite, phyllite. Age: Ordovician to Triassic, 202 to 487 million years old. About 4 mi of the line.
Mafic-volcanic, greenstone. Age: Paleozoic to Mesozoic, 66 to 542 million years old. About 3 mi of the line.
Peridotite, serpentinite. Age: Neoproterozoic to Early Jurassic, 175 to 1,000 million years old. About 2 mi of the line.
Diorite, gabbro. Age: Triassic to Cretaceous, 66 to 252 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 Alleghany reaches San Francisco Bay and the Pacific Ocean by way of North Fork Kanaka Creek, Kanaka Creek, the Middle Yuba, the Yuba, the Feather and the Sacramento: about 170 river miles.
75 miles of the trip are on the Sacramento.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Alleghany; river miles along the main stem, rounded.
Alleghany has a warm-summer Mediterranean climate. Summer afternoons average 85° in July; winter nights fall to about 30° in January. A normal year brings about 82 inches of snow; with the rain, that comes to about 82 inches of water.
On November 14 Alleghany normally reaches 58° and falls to 34°. The record high is 80°, in 1995; the record low 18°, in 1985. The most rain on this date, 5.28 in, fell in 1963.
Normals 1991–2020 and records since 1948 at Strawberry Valley 2, 18 miles west-northwest, 410 ft lower. NOAA, through RCC-ACIS.
