The O'Brien 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.
Showers likely
Showers likely
Chance of showers
Showers likely
Showers likely
Chance of showers
Mostly cloudy
O'Brien’s center stands about 1,420 ft above sea level. Within three miles the land runs from 1,350 ft to 2,930 ft, a difference of 1,580 ft: steep hill country. The highest named summit within 15 miles is El Capitan, about 6,750 ft, 14 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 5×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Peridotite, serpentinite. Age: Paleozoic to Jurassic, 145 to 542 million years old. About 10 mi of the line.
Serpentinite. Age: Jurassic, 145 to 202 million years old. About 3 mi of the line.
Mafic-volcanic, greenstone. Age: Paleozoic to Mesozoic, 66 to 542 million years old. About 2 mi of the line.
Gravel, boulders, clay. Age: Pleistocene to Holocene, less than 2.6 million years old. About 2 mi of the line.
Peridotite, serpentinite. Age: Neoproterozoic to Early Jurassic, 175 to 1,000 million years old. About 2 mi of the line.
Mudstone, graywacke. Age: Late Jurassic, 153 to 164 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. 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.
A raindrop that lands in O'Brien reaches the Pacific Ocean by way of the West Fork Illinois, the Illinois and the Rogue: about 90 river miles.
55 miles of the trip are on the Illinois.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of O'Brien; river miles along the main stem, rounded.
