The St. Thomas 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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St. Thomas’s center stands about 840 ft above sea level. Within three miles the land runs from 820 ft to 860 ft, a difference of 40 ft: nearly flat ground.
Under the town center the state geologic map shows Mowry-Skull Creek, Undivided (shale, sandstone), from the Early Cretaceous to Late Cretaceous, 66 to 145 million years old.
The section below crosses 2 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.
Shale, sandstone. Age: Early Cretaceous to Late Cretaceous, 66 to 145 million years old. About 13 mi of the line.
Shale. Age: Jurassic, 145 to 202 million years old. About 12 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 St. Thomas reaches Hudson Bay by way of Willow Creek, the Park, the Red River of the North and the Nelson: about 890 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 St. Thomas; river miles along the main stem, rounded.
