The Discovery Bay 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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84° on Nov. 14, 1995, the hottest reading for this week of the year since 1955. Next is 79° in 1990.
Discovery Bay’s center stands barely above sea level. Within three miles the land runs from -20 ft to 30 ft, a difference of 50 ft: nearly flat ground. The highest named summit within 15 miles is Brushy Peak, about 1,680 ft, 11 miles south-southwest.
Under the town center the state geologic map shows Quaternary alluvium and marine deposits (coarse-detrital), from the Pleistocene to Holocene, less than 2.6 million years old.
The section below crosses 3 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 37×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 18 mi of the line.
Sandstone, siltstone-mudstone. Age: Late Cretaceous, 66 to 100 million years old. About 3 mi of the line.
Sandstone, conglomerate. Age: Miocene to Pleistocene, less than 23 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.
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 Discovery Bay reaches San Francisco Bay and the Pacific Ocean by way of the Old, the San Joaquin and New York Slough: about 35 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Discovery Bay; river miles along the main stem, rounded.
Discovery Bay has a cold semi-arid climate. Summer afternoons average 93° in July; winter nights fall to about 40° in December. About 12 inches of rain fall in a normal year.
On November 14 Discovery Bay normally reaches 66° and falls to 46°. The record high is 84°, in 1995; the record low 32°, in 1961. The most rain on this date, 0.60 in, fell in 1972.
Normals 1991–2020 and records since 1955 at Tracy Pumping Plant, 8 miles south. NOAA, through RCC-ACIS.
