The Bigfork 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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Bigfork’s center stands about 1,310 ft above sea level. Within three miles the land runs from 1,300 ft to 1,410 ft, a difference of 110 ft: gently rolling country.
Under the town center the state geologic map shows Volcaniclastic rocks of felsic to intermediate composition (felsic-volcanic), from the Neoarchean, 2.5 to 2.8 billion 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 64×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Felsic-volcanic. Age: Neoarchean, 2.5 to 2.8 billion years old. About 15 mi of the line.
Granitic. Age: Neoarchean, 2.5 to 2.8 billion years old. About 4 mi of the line.
Komatiite, mafic-volcanic. Age: Neoarchean, 2.5 to 2.8 billion years old. About 3 mi of the line.
Gabbro, pyroxenite, diorite. Age: Neoarchean, 2.5 to 2.8 billion 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.
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 Bigfork reaches Hudson Bay by way of the Big Fork, the Rainy, the Winnipeg and the Nelson: about 1,050 river miles. Past the border it runs north through Canada to Hudson Bay.
Lakes on the way: Lake of the Woods and Lake Winnipeg.
400 miles of the trip are on the Nelson.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Bigfork; river miles along the main stem, rounded.
