The Isabel 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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Isabel’s center stands about 1,850 ft above sea level. Within three miles the land runs from 1,800 ft to 1,870 ft, a difference of 70 ft: gently rolling country.
Under the town center the state geologic map shows Dune Sand, from the Pleistocene to Holocene, less than 2.6 million years old.
The section below crosses 4 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 52×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sand. Age: Pleistocene to Holocene, less than 2.6 million years old. About 10 mi of the line.
Siltstone, sandstone, shale. Age: Permian, 252 to 299 million years old. About 6 mi of the line.
Silt. Age: Pleistocene to Holocene, less than 2.6 million years old. About 6 mi of the line.
Sand, silt, clay. Age: Pleistocene, 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 Isabel reaches the Gulf of America by way of Chicken Creek, Sand Creek, the Chikaskia, the Salt Fork Arkansas, the Arkansas and the Mississippi: about 1,370 river miles.
Lakes on the way: Murray Lake and Ozark Lake.
600 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Isabel; river miles along the main stem, rounded.
