The Third River 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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Third River’s center stands about 1,350 ft above sea level. Within three miles the land runs from 1,310 ft to 1,390 ft, a difference of 80 ft: gently rolling country.
Under the town center the state geologic map shows Mafic metavolcanic rocks (metabasalt, greenstone), from the Neoarchean, 2.5 to 2.8 billion years old.
The section below crosses 5 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.
Tonalite, granodiorite, diorite. Age: Neoarchean, 2.5 to 2.8 billion years old. About 9 mi of the line.
Metabasalt, greenstone. Age: Neoarchean, 2.5 to 2.8 billion years old. About 6 mi of the line.
Granitic. Age: Neoarchean, 2.5 to 2.8 billion years old. About 3 mi of the line.
Felsic-volcanic. Age: Neoarchean, 2.5 to 2.8 billion years old. About 3 mi of the line.
Granitic. 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 Third River reaches the Gulf of America by way of Sugar Lake and the Mississippi: about 2,230 river miles.
Lakes on the way: Sugar Lake and Lake Pepin.
1,750 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Third River; river miles along the main stem, rounded.
