The Ione 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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Ione’s center stands about 310 ft above sea level. Within three miles the land runs from 230 ft to 780 ft, a difference of 550 ft: hilly country. The highest named summit within 15 miles is Clinton Peak, about 2,420 ft, 14 miles east.
Under the town center the state geologic map shows Eocene nonmarine rocks, unit 1 (Northern and Central California) (sandstone), from the Eocene, 34 to 56 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 11×. 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, conglomerate. Age: Miocene to Pleistocene, less than 23 million years old. About 6 mi of the line.
Mafic-volcanic. Age: Jurassic, 145 to 202 million years old. About 5 mi of the line.
Argillite, quartzite, phyllite. Age: Ordovician to Triassic, 202 to 487 million years old. About 4 mi of the line.
Slate, graywacke. Age: Triassic to Late Jurassic, 145 to 252 million years old. About 4 mi of the line.
Sandstone. Age: Eocene, 34 to 56 million years old. About 3 mi of the line.
Sandstone, conglomerate. Age: Oligocene to Pleistocene, less than 34 million years old. About 3 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 Ione reaches San Francisco Bay and the Pacific Ocean by way of Dry Creek, the Mokelumne, the South Mokelumne, the San Joaquin and New York Slough: about 85 river miles.
Often dry. About 30% 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 Ione; river miles along the main stem, rounded.
