The St. Pierre 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. Pierre’s center stands about 4,150 ft above sea level. Within three miles the land runs from 3,360 ft to 5,410 ft, a difference of 2,050 ft: mountain country. The highest named summit within 15 miles is Baldy Mountain, about 6,890 ft, 10 miles southeast.
Under the town center the state geologic map shows Mafic volcanic rock (mafic-volcanic), from the Tertiary, 2.6 to 66 million years old.
The section below crosses 14 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 6×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sandstone, shale. Age: Late Cretaceous, 72 to 84 million years old. About 7 mi of the line.
Mafic-volcanic. Age: Tertiary, 2.6 to 66 million years old. About 6 mi of the line.
Shale. Age: Late Cretaceous, 72 to 84 million years old. About 3 mi of the line.
Syenitic, syenite. Age: Tertiary, 2.6 to 66 million years old. About 2 mi of the line.
Felsic-volcanic. Age: Tertiary, 2.6 to 66 million years old. About 1 mi of the line.
Shale. Age: Late Cretaceous, 72 to 84 million years old. 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. 8 smaller units along the line are not listed.
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. Pierre reaches the Gulf of America by way of Boxelder Creek, Big Sandy Creek, the Milk River, the Missouri and the Mississippi: about 3,420 river miles.
Lakes on the way: Lake Oahe, Lake Sakakawea, Lake Sharpe and Lake Francis Case.
1,170 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of St. Pierre; river miles along the main stem, rounded.
