The Acton 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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88° on Nov. 16, 1992, the hottest reading for this week of the year since 1931. Next is 85° in 1995.
Acton’s center stands about 2,710 ft above sea level. Within three miles the land runs from 2,510 ft to 3,690 ft, a difference of 1,180 ft: steep hill country. The highest named summit within 15 miles is Pacifico Mountain, about 7,100 ft, 11 miles east-southeast.
Under the town center the state geologic map shows Mesozoic granitic rocks, unit 3 (Sierra Nevada, Death Valley area, Northern Mojave Desert and Transverse Ranges) (granodiorite), from the Permian to Tertiary, 2.6 to 260 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.
Quartz-monzonite. Age: Late Triassic, 218 to 218 million years old. About 8 mi of the line.
Granodiorite. Age: Permian to Tertiary, 2.6 to 260 million years old. About 7 mi of the line.
Mica-schist. Age: Late Cretaceous to Eocene, 34 to 100 million years old. About 6 mi of the line.
Orthogneiss. Age: Paleoproterozoic to Miocene, 5.3 to 2,500 million years old. About 1 mi of the line.
Anorthosite, gabbro. Age: Mesoproterozoic, 1.2 to 1.2 billion years old. About 1 mi of the line.
Coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 0.5 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 Acton reaches the Pacific Ocean by way of the Santa Clara: about 75 river miles.
60 miles of the trip are on the Santa Clara.
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 Acton; river miles along the main stem, rounded.
Acton has a cold desert climate. Summer afternoons average 98° in August; winter nights fall to about 32° in December. About 6 inches of rain fall in a normal year.
On November 14 Acton normally reaches 68° and falls to 38°. The record high is 84°, in 1932; the record low 24°, in 1938. The most rain on this date, 0.81 in, fell in 1946.
Normals 1991–2020 and records since 1931 from the Palmdale Area threaded record (Palmdale Airport, 13 miles north-northeast, 200 ft lower). NOAA, through RCC-ACIS.
