The Petaluma Center 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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91° on Nov. 17, 1932, the hottest reading for this week of the year since 1893. Next is 85° in 1923.
Petaluma Center’s center stands about 90 ft above sea level. Within three miles the land runs from 60 ft to 690 ft, a difference of 630 ft: hilly country. The highest named summit within 15 miles is Sonoma Mountain, about 2,290 ft, 13 miles east-northeast.
Under the town center the state geologic map shows Franciscan melange, from the Jurassic to Cretaceous, 66 to 202 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 12×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Melange. Age: Jurassic to Cretaceous, 66 to 202 million years old. About 7 mi of the line.
Sandstone, mudstone. Age: Miocene to Pleistocene, less than 23 million years old. About 5 mi of the line.
Dacite. Age: Late Miocene to Late Pliocene, 3 to 7 million years old. About 3 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 2 mi of the line.
Sandstone, conglomerate. Age: Miocene to Pleistocene, less than 23 million years old. About 2 mi of the line.
Sandstone, mudstone. Age: Jurassic to Cretaceous, 66 to 202 million years old. About 2 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 Petaluma Center reaches the Pacific Ocean by way of Stemple Creek and the Estero de San Antonio: about 16 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Petaluma Center; river miles along the main stem, rounded.
Petaluma Center has a warm-summer Mediterranean climate. Summer afternoons average 82° in September; winter nights fall to about 38° in December. About 26 inches of rain fall in a normal year.
On November 14 Petaluma Center normally reaches 66° and falls to 43°. The record high is 83°, in 2010; the record low 20°, in 1916. The most rain on this date, 1.77 in, fell in 1953.
Normals 1991–2020 and records since 1893 at Petaluma Airport, 10 miles east. NOAA, through RCC-ACIS.
