The Helgeland 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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Helgeland’s center stands about 940 ft above sea level. Within three miles the land runs from 910 ft to 970 ft, a difference of 60 ft: nearly flat ground.
Under the town center the state geologic map shows Granite to granodiorite (granite, granodiorite), 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.
Granodiorite, diorite. Age: Neoarchean, 2.5 to 2.8 billion years old. About 15 mi of the line.
Granite, granodiorite. Age: Neoarchean, 2.5 to 2.8 billion years old. About 6 mi of the line.
Tonalite, granodiorite, diorite. Age: Neoarchean, 2.5 to 2.8 billion years old. About 2 mi of the line.
Plutonic. Age: Archean. About 0.9 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 Helgeland reaches Hudson Bay by way of the South Branch Snake, the Snake, the Red River of the North and the Nelson: about 930 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 Helgeland; river miles along the main stem, rounded.
