The Long Lake 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.
Long Lake’s center stands about 1,950 ft above sea level. Within three miles the land runs from 1,910 ft to 2,000 ft, a difference of 90 ft: gently rolling country.
Under the town center the state geologic map shows Pierre Shale (shale, bentonite), from the Late Cretaceous, 66 to 100 million years old.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 46×. 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, bentonite. Age: Late Cretaceous, 66 to 100 million years old. About 24 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.