The Hornitos 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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22° on Nov. 15, 1905, the coldest reading for this week of the year since 1899. Next is 24° in 1938.
Hornitos’s center stands about 840 ft above sea level. Within three miles the land runs from 520 ft to 1,230 ft, a difference of 710 ft: hilly country. The highest named summit within 15 miles is Bullion Knob, about 4,220 ft, 12 miles east.
Under the town center the state geologic map shows Jurassic marine rocks, unit 1 (Western Sierra Nevada and Western Klamath Mountains) (slate, graywacke), from the Triassic to Late Jurassic, 145 to 252 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 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.
Mafic-volcanic. Age: Jurassic, 145 to 202 million years old. About 9 mi of the line.
Slate, graywacke. Age: Triassic to Late Jurassic, 145 to 252 million years old. About 6 mi of the line.
Sandstone, conglomerate. Age: Miocene to Pleistocene, less than 23 million years old. About 6 mi of the line.
Sandstone. Age: Eocene, 34 to 56 million years old. About 2 mi of the line.
Sandstone, conglomerate. Age: Oligocene to Pleistocene, less than 34 million years old. About 1 mi of the line.
Peridotite, serpentinite. Age: Neoproterozoic to Early Jurassic, 175 to 1,000 million years old. About 0.4 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 Hornitos reaches San Francisco Bay and the Pacific Ocean by way of Burns Creek, Bear Creek, the San Joaquin and New York Slough: about 190 river miles.
130 miles of the trip are on the San Joaquin.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Hornitos; river miles along the main stem, rounded.
Hornitos has a cold semi-arid climate. Summer afternoons average 96° in July; winter nights fall to about 36° in December. About 12 inches of rain fall in a normal year.
On November 14 Hornitos normally reaches 67° and falls to 41°. The record high is 81°, in 1933; the record low 25°, in 1938. The most rain on this date, 1.57 in, fell in 1953.
Normals 1991–2020 and records since 1899 from the Merced Area threaded record (Merced Municipal Airport, 21 miles southwest, 690 ft lower). NOAA, through RCC-ACIS.
