The Clayton 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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Clayton’s center stands about 440 ft above sea level. Within three miles the land runs from 240 ft to 2,010 ft, a difference of 1,770 ft: steep hill country. The highest named summit within 15 miles is Mount Diablo, about 3,810 ft, 4 miles south-southeast.
Under the town center the state geologic map shows Lower Cretaceous marine rocks (siltstone-mudstone), from the Early Cretaceous, 113 to 145 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 6×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Mudstone, sandstone. Age: Paleocene to Oligocene, 23 to 66 million years old. About 5 mi of the line.
Sandstone, conglomerate. Age: Miocene to Pleistocene, less than 23 million years old. About 3 mi of the line.
Siltstone-mudstone. Age: Early Cretaceous, 113 to 145 million years old. About 3 mi of the line.
Sandstone, mudstone. Age: Jurassic to Cretaceous, 66 to 202 million years old. About 3 mi of the line.
Coarse-detrital. Age: Pleistocene, 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.
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 Clayton reaches San Francisco Bay and the Pacific Ocean by way of Mount Diablo Creek and Hastings Slough: about 13 river miles.
Often dry. About 70% of the way is mapped as streams that run only after rain or snowmelt; the water makes the whole trip in floods.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Clayton; river miles along the main stem, rounded.
