The Descanso 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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81° on Nov. 12, 1894, the hottest reading for this week of the year since 1893. Next is 80° in 2025.
Descanso’s center stands about 3,420 ft above sea level. Within three miles the land runs from 2,820 ft to 4,590 ft, a difference of 1,770 ft: steep hill country. The highest named summit within 15 miles is Cuyamaca Peak, about 6,480 ft, 6 miles north.
Under the town center the state geologic map shows Mesozoic granitic rocks, unit 2 (Peninsular Ranges) (tonalite), from the Middle Jurassic to Late Cretaceous, 66 to 175 million years old.
The section below crosses 4 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.
Tonalite. Age: Middle Jurassic to Late Cretaceous, 66 to 175 million years old. About 19 mi of the line.
Diorite, gabbro. Age: Triassic to Cretaceous, 66 to 252 million years old. About 3 mi of the line.
Pelitic-schist. Age: Triassic, 202 to 252 million years old. About 2 mi of the line.
Plutonic, gneiss. Age: Paleoproterozoic to Late Cretaceous, 66 to 2,500 million years old. About 0.6 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 Descanso reaches the Pacific Ocean by way of the Sweetwater: about 45 river miles.
Often dry. About 30% of the way is mapped as streams that run only after rain or snowmelt; the water makes the whole trip in floods.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Descanso; river miles along the main stem, rounded.
Descanso has a hot-summer Mediterranean climate. Summer afternoons average 86° in August; winter nights fall to about 38° in December. A normal year brings about 6 inches of snow; with the rain, that comes to about 24 inches of water.
On November 14 Descanso normally reaches 60° and falls to 44°. The record high is 77°, in 2016; the record low 31°, in 2022. The most rain on this date, 1.60 in, fell in 1909.
Normals 1991–2020 and records since 1893 at Julian Cdf, 15 miles north, 800 ft higher. NOAA, through RCC-ACIS.
