The Simla 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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Simla’s center stands about 5,990 ft above sea level. Within three miles the land runs from 5,880 ft to 6,340 ft, a difference of 460 ft: hilly country. The highest named summit within 15 miles is Eagle Rock, about 6,220 ft, 11 miles west-northwest.
Under the town center the state geologic map shows Denver Fm or lower part of Dawson Arkose (arkose, shale, mudstone), from the Late Cretaceous to Paleocene, 56 to 100 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 20×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Arkose, shale, mudstone. Age: Late Cretaceous to Paleocene, 56 to 100 million years old. About 17 mi of the line.
Gravel, unconsolidated. Age: Pleistocene, 0.2 to 1.6 million years old. About 4 mi of the line.
Arkose, conglomerate, shale. Age: Paleocene to Eocene, 34 to 66 million years old. About 1 mi of the line.
Shale, claystone, sandstone. Age: Late Cretaceous, 66 to 100 million years old. About 1 mi of the line.
Unconsolidated. Age: Quaternary, less than 2.6 million years old. About 0.8 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 Simla reaches the Gulf of America by way of Big Sandy Creek, the Arkansas and the Mississippi: about 1,870 river miles.
Lakes on the way: Murray Lake and Ozark Lake.
800 miles of the trip are on the Arkansas.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Simla; river miles along the main stem, rounded.
