The Alma 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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Alma’s center stands about 890 ft above sea level. Within three miles the land runs from 860 ft to 930 ft, a difference of 70 ft: gently rolling country.
Under the town center the state geologic map shows Upper Ordovician (limestone, dolostone), from the Late Ordovician, 445 to 459 million 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.
Limestone, dolostone. Age: Late Ordovician, 445 to 459 million years old. About 7 mi of the line.
Conglomerate, sandstone, mudstone. Age: Late Cretaceous, 72 to 100 million years old. About 6 mi of the line.
Metabasalt, greenstone. Age: Neoarchean, 2.5 to 2.8 billion years old. About 5 mi of the line.
Tonalite, granodiorite, diorite. Age: Neoarchean, 2.5 to 2.8 billion years old. About 5 mi of the line.
Granitic. Age: Neoarchean, 2.5 to 2.8 billion years old. About 1 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 Alma reaches Hudson Bay by way of the Tamarac, the Red River of the North and the Nelson: about 900 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 Alma; river miles along the main stem, rounded.
