The Darby 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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Darby’s center stands about 3,890 ft above sea level. Within three miles the land runs from 3,820 ft to 5,150 ft, a difference of 1,330 ft: steep hill country. The highest named summit within 15 miles is Trapper Peak, about 10,030 ft, 11 miles south-southwest.
Under the town center the state geologic map shows Gravel, from the Pleistocene to Holocene, less than 1.8 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 4×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Granitic. Age: Cretaceous, 66 to 145 million years old. About 17 mi of the line.
Granitic. Age: Tertiary, 2.6 to 66 million years old. About 3 mi of the line.
Unconsolidated. Age: Pleistocene to Holocene, less than 1.8 million years old. About 2 mi of the line.
Conglomerate, sandstone, siltstone. Age: Early Miocene to Pliocene, 2.6 to 20 million years old. About 2 mi of the line.
Age: Pleistocene to Holocene, less than 1.8 million years old. About 0.7 mi of the line.
Gravel, sand, silt. Age: Pleistocene to Holocene, less than 1.8 million years old. About 0.6 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 Darby reaches the Pacific Ocean by way of the Bitterroot, the Clark Fork, the Pend Oreille and the Columbia: about 1,140 river miles.
Lakes on the way: Lake Pend Oreille, Lake Umatilla and Noxon Rapids Reservoir.
460 miles of the trip are on the Columbia.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Darby; river miles along the main stem, rounded.
