The Emerald Lake Hills 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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3.29 inches of rain fell in two days, the most for this week of the year since records began in 1906. The next wettest, 3.22 inches, fell in 1981.
Emerald Lake Hills’s center stands about 420 ft above sea level. Within three miles the land runs from 10 ft to 1,370 ft, a difference of 1,360 ft: steep hill country. The highest named summit within 15 miles is Black Mountain, about 2,810 ft, 12 miles south-southeast.
The section below crosses 10 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 8×. 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: Jurassic to Cretaceous, 66 to 202 million years old. About 6 mi of the line.
Coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 4 mi of the line.
Mudstone, sandstone. Age: Paleocene to Oligocene, 23 to 66 million years old. About 3 mi of the line.
Serpentinite. Age: Middle Jurassic to Late Jurassic, 145 to 175 million years old. About 2 mi of the line.
Greenstone. Age: Jurassic to Cretaceous, 66 to 202 million years old. About 1 mi of the line.
Sandstone, conglomerate. Age: Miocene to Pleistocene, less than 23 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. 4 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.
Rain that falls on Emerald Lake Hills runs straight into San Francisco Bay and the Pacific Ocean.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Emerald Lake Hills; river miles along the main stem, rounded.
Emerald Lake Hills has a warm-summer Mediterranean climate. Summer afternoons average 81° in July; winter nights fall to about 40° in January. About 19 inches of rain fall in a normal year.
On November 14 Emerald Lake Hills normally reaches 65° and falls to 44°. The record high is 79°, in 2010; the record low 29°, in 1935. The most rain on this date, 1.72 in, fell in 1953.
Normals 1991–2020 and records since 1906 at Redwood City, here, 390 ft lower. NOAA, through RCC-ACIS.
