The Grimstad 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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Grimstad’s center stands about 1,130 ft above sea level. Within three miles the land runs from 1,090 ft to 1,170 ft, a difference of 80 ft: gently rolling country.
Under the town center the state geologic map shows Schist of sedimentary protolith, from the Neoarchean, 2.5 to 2.8 billion 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 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.
Schist. Age: Neoarchean, 2.5 to 2.8 billion years old. About 12 mi of the line.
Felsic-volcanic. Age: Neoarchean, 2.5 to 2.8 billion years old. About 7 mi of the line.
Metabasalt, greenstone. Age: Neoarchean, 2.5 to 2.8 billion years old. About 2 mi of the line.
Tonalite, granodiorite, diorite. Age: Neoarchean, 2.5 to 2.8 billion years old. About 2 mi of the line.
Granodiorite, diorite. Age: Neoarchean, 2.5 to 2.8 billion years old. About 0.6 mi of the line.
Gabbro, peridotite, pyroxenite. Age: Neoarchean, 2.5 to 2.8 billion 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 Grimstad reaches Hudson Bay by way of the South Fork Roseau, the Roseau, the Red River of the North and the Nelson: about 870 river miles. Past the border it runs north through Canada to Hudson Bay.
Lake on the way: 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 Grimstad; river miles along the main stem, rounded.
