The Piedra 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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Piedra’s center stands about 7,860 ft above sea level. Within three miles the land runs from 7,660 ft to 8,950 ft, a difference of 1,290 ft: steep hill country. The highest named summit within 15 miles is South River Peak, about 13,040 ft, 14 miles northeast.
Under the town center the state geologic map shows Mancos Shale (shale, sandstone), from the Early Cretaceous to Late Cretaceous, 66 to 145 million years old.
The section below crosses 12 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 4×. 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, claystone. Age: Late Jurassic, 145 to 164 million years old. About 6 mi of the line.
Volcanic. Age: Oligocene, 23 to 34 million years old. About 5 mi of the line.
Shale, sandstone. Age: Early Cretaceous to Late Cretaceous, 66 to 145 million years old. About 3 mi of the line.
Sandstone, shale, conglomerate. Age: Early Cretaceous to Late Cretaceous, 66 to 145 million years old. About 2 mi of the line.
Andesite. Age: Oligocene, 23 to 34 million years old. About 2 mi of the line.
Unconsolidated. 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. 6 smaller units 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 Piedra reaches the Gulf of California by way of the East Fork Piedra, the Piedra, the San Juan and the Colorado: about 1,220 river miles.
Lakes on the way: Lake Mead, Lake Powell, Lake Mohave and Lake Havasu.
Seldom reaches the sea. Dams and canals now take nearly all of the Colorado before its old delta in Mexico.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Piedra; river miles along the main stem, rounded.
