The Swan Lake 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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Swan Lake’s center stands about 4,790 ft above sea level. Within three miles the land runs from 3,060 ft to 6,810 ft, a difference of 3,750 ft: mountain country. The highest named summit within 15 miles is Prospector Mountain, about 8,030 ft, 14 miles northeast.
Under the town center the state geologic map shows Ravalli Group: St. Regis, Revett, and Burke Formations; or Empire and Grinnell Formations; or Empire and Spokane Formations (quartzite, argillite, metasiltstone), from the Mesoproterozoic, 1 to 1.6 billion years old.
The section below crosses 7 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.
Quartzite, metasiltstone, argillite. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 8 mi of the line.
Unconsolidated. Age: Pleistocene to Holocene, less than 1.8 million years old. About 6 mi of the line.
Quartzite, argillite, metasiltstone. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 4 mi of the line.
Metasiltstone, argillite. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 3 mi of the line.
Metasiltstone, argillite, quartzite. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 2 mi of the line.
Age: Pleistocene to Holocene, less than 1.8 million years old. About 0.5 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 1 smaller unit 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 Swan Lake reaches the Pacific Ocean by way of Swan Lake, the Swan River, the Flathead, the Clark Fork, the Pend Oreille and the Columbia: about 1,090 river miles.
Lakes on the way: Flathead Lake, 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 Swan Lake; river miles along the main stem, rounded.
