The Green Grass 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.
Partly cloudy
Sunny; warmer
Mostly sunny
Partly cloudy
Partly cloudy; cooler
Partly cloudy
Chance of showers
Green Grass’s center stands about 2,020 ft above sea level. Within three miles the land runs from 1,850 ft to 2,320 ft, a difference of 470 ft: hilly country. The highest named summit within 15 miles is Eagle Butte, about 2,460 ft, 14 miles south-southeast.
Under the town center the state geologic map shows Pierre Shale (shale, bentonite), from the Late Cretaceous, 66 to 100 million years old.
The section below crosses 3 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 32×. 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, siltstone. Age: Late Cretaceous, 66 to 100 million years old. About 19 mi of the line.
Shale, bentonite. Age: Late Cretaceous, 66 to 100 million years old. About 3 mi of the line.
Coarse-detrital, fine-detrital. Age: Quaternary, less than 2.6 million years old. About 2 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 Green Grass reaches the Gulf of America by way of the Moreau, the Missouri and the Mississippi: about 2,440 river miles.
Lakes on the way: Lake Oahe, Lake Sharpe, Lake Francis Case and Lewis and Clark Lake.
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 Green Grass; river miles along the main stem, rounded.
