The Rocksprings 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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Rocksprings’s center stands about 2,390 ft above sea level. Within three miles the land runs from 2,260 ft to 2,410 ft, a difference of 150 ft: gently rolling country.
Under the town center the state geologic map shows Buda Limestone and Del Rio Clay, undivided, from the Late Cretaceous, 66 to 100 million years old.
The section below crosses 3 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 42×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Limestone. Age: Early Cretaceous, 100 to 113 million years old. About 20 mi of the line.
Limestone. Age: Late Cretaceous, 66 to 100 million years old. About 3 mi of the line.
Limestone. Age: Late Cretaceous, 66 to 100 million years old. About 0.5 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 Rocksprings reaches the Gulf of America by way of the South Llano, the Llano and the Colorado: about 560 river miles.
Lakes on the way: 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 Rocksprings; river miles along the main stem, rounded.
