The Roby 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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Roby’s center stands about 1,970 ft above sea level. Within three miles the land runs from 1,890 ft to 2,010 ft, a difference of 120 ft: gently rolling country.
Under the town center the state geologic map shows Quaternary deposit, undivided (coarse-detrital, fine-detrital), from the Quaternary, 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 44×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Coarse-detrital, fine-detrital. Age: Quaternary, less than 2.6 million years old. About 9 mi of the line.
Sandstone, shale. Age: Permian, 252 to 299 million years old. About 6 mi of the line.
Sand. Age: Holocene, less than 12,000 years old. About 3 mi of the line.
Shale. Age: Permian, 252 to 299 million years old. About 2 mi of the line.
Shale. Age: Permian, 252 to 299 million years old. About 2 mi of the line.
Shale. Age: Middle Triassic to Late Triassic, 208 to 247 million years old. About 1 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 Roby reaches the Gulf of America by way of Cottonwood Creek, the Clear Fork and the Brazos: about 1,020 river miles.
Lakes on the way: Possum Kingdom Lake and Lake Granbury.
550 miles of the trip are on the Brazos.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Roby; river miles along the main stem, rounded.
