The Nicasio 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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82° on Nov. 14, 2008, the hottest reading for this week of the year since 1894. Next is 82° in 2010.
Nicasio’s center stands about 200 ft above sea level. Within three miles the land runs from 160 ft to 1,310 ft, a difference of 1,150 ft: steep hill country. The highest named summit within 15 miles is Mount Tamalpais, about 2,570 ft, 11 miles south-southeast.
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 9 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 13×. 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 5 mi of the line.
Sandstone, mudstone. Age: Jurassic to Cretaceous, 66 to 202 million years old. About 3 mi of the line.
Mica-schist. Age: Early Cretaceous, 110 to 143 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, mudstone. Age: Oligocene to Pliocene, 2.6 to 34 million years old. About 2 mi of the line.
Andesite, dacite. Age: Middle Miocene to Late Miocene, 9.5 to 13 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. 3 smaller units 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 Nicasio reaches the Pacific Ocean by way of Nicasio Creek and Lagunitas Creek: about 12 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Nicasio; river miles along the main stem, rounded.
Nicasio has a warm-summer Mediterranean climate. Summer afternoons average 81° in July; winter nights fall to about 42° in December. About 34 inches of rain fall in a normal year.
On November 14 Nicasio normally reaches 65° and falls to 46°. The record high is 82°, in 2008; the record low 30°, in 1894. The most rain on this date, 2.10 in, fell in 1953.
Normals 1991–2020 and records since 1894 at San Rafael-Civic Center, 10 miles east-southeast. NOAA, through RCC-ACIS.
