The Avalon 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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Avalon’s center stands about 130 ft above sea level. Within three miles the land runs from 10 ft to 1,600 ft, a difference of 1,590 ft: steep hill country. Open water lies within three miles. The highest named summit within 15 miles is Mount Orizaba, about 2,090 ft, 6 miles west-northwest.
Under the town center the state geologic map shows Cenozoic (Tertiary) granitic rocks, unit 2 (Catalina Island) (quartz-diorite), from the Early Miocene to Middle Miocene, 12 to 19 million years old.
The section below crosses 4 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 12×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Quartz-diorite. Age: Early Miocene to Middle Miocene, 12 to 19 million years old. About 6 mi of the line.
Basalt, andesite. Age: Late Oligocene to Late Miocene, 8 to 25 million years old. About 3 mi of the line.
Schist, metasedimentary. Age: Early Cretaceous to Late Cretaceous, 95 to 112 million years old. About 1 mi of the line.
Greenstone. Age: Jurassic to Cretaceous, 66 to 202 million years old. About 0.4 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.
Rain that falls on Avalon runs straight into the Pacific Ocean.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Avalon; river miles along the main stem, rounded.
