The Bloomfield 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. 17, 1961, the coldest reading for this week of the year since 1926. Next is 22° in 1978.
Bloomfield’s center stands about 60 ft above sea level. Within three miles the land runs from 30 ft to 820 ft, a difference of 790 ft: hilly country. The highest named summit within 15 miles is Sonoma Mountain, about 2,290 ft, 15 miles east.
Under the town center the state geologic map shows Pliocene marine rocks (sandstone, mudstone), from the Miocene to Pleistocene, less than 23 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 21×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sandstone, mudstone. Age: Miocene to Pleistocene, less than 23 million years old. About 11 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 4 mi of the line.
Sandstone, conglomerate. Age: Miocene to Pleistocene, less than 23 million years old. About 2 mi of the line.
Dacite. Age: Late Miocene to Late Pliocene, 3 to 7 million years old. About 1 mi of the line.
Melange. Age: Jurassic to Cretaceous, 66 to 202 million years old. About 0.7 mi of the line.
Coarse-detrital. Age: Pleistocene, less than 2.6 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 Bloomfield reaches the Pacific Ocean by way of Americano Creek and the Estero Americano: about 14 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Bloomfield; river miles along the main stem, rounded.
Bloomfield has a warm-summer Mediterranean climate. Summer afternoons average 84° in August; winter nights fall to about 37° in January. About 40 inches of rain fall in a normal year.
On November 14 Bloomfield normally reaches 67° and falls to 40°. The record high is 85°, in 2008; the record low 25°, in 1985. The most rain on this date, 2.44 in, fell in 1972.
Normals 1991–2020 and records since 1926 at Graton, 8 miles north, 140 ft higher. NOAA, through RCC-ACIS.
