The Blackwell 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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Blackwell’s center stands about 2,110 ft above sea level. Within three miles the land runs from 1,980 ft to 2,190 ft, a difference of 210 ft: rolling country. The highest named summit within 15 miles is Horse Mountain, about 2,510 ft, 13 miles west-southwest.
Under the town center the state geologic map shows Seymour Formation (conglomerate), from the Pleistocene, less than 2.6 million years old.
The section below crosses 7 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 29×. 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-mudstone. Age: Permian, 252 to 299 million years old. About 9 mi of the line.
Limestone. Age: Early Cretaceous, 100 to 113 million years old. About 4 mi of the line.
Sandstone, shale. Age: Permian, 252 to 299 million years old. About 3 mi of the line.
Conglomerate. Age: Pleistocene, less than 2.6 million years old. About 3 mi of the line.
Sandstone, claystone. Age: Early Cretaceous, 100 to 145 million years old. About 2 mi of the line.
Shale. Age: Permian, 252 to 299 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. 1 smaller unit 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 Blackwell reaches the Gulf of America by way of Oak Creek and the Colorado: about 720 river miles.
Lakes on the way: Buchanan Lake, Lake Marble Falls and Lake Lyndon B Johnson.
320 miles of the trip are on the Colorado.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Blackwell; river miles along the main stem, rounded.
