The O'Brien 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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O'Brien’s center stands about 1,570 ft above sea level. Within three miles the land runs from 1,500 ft to 1,590 ft, a difference of 90 ft: gently rolling country. The highest named summit within 15 miles is Buzzard Peak, about 1,830 ft, 14 miles northwest.
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 64×. 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: Holocene, less than 12,000 years old. About 13 mi of the line.
Sand. Age: Holocene, less than 12,000 years old. About 7 mi of the line.
Claystone. Age: Permian, 252 to 299 million years old. About 3 mi of the line.
Sand. Age: Pleistocene to Holocene, less than 2.6 million years old. About 0.9 mi of the line.
Fine-detrital, coarse-detrital. Age: Holocene, less than 12,000 years old. About 0.6 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 O'Brien reaches the Gulf of America by way of China Branch and the Brazos: about 900 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 O'Brien; river miles along the main stem, rounded.
