The Johnson City 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.
Mostly cloudy
Showers likely
Mostly cloudy; cooler
Mostly sunny
Mostly cloudy
Chance of showers
Partly cloudy
Johnson City’s center stands about 1,260 ft above sea level. Within three miles the land runs from 1,080 ft to 1,500 ft, a difference of 420 ft: hilly country. The highest named summit within 15 miles is Monument Hill, about 1,790 ft, 4 miles southwest.
Under the town center the state geologic map shows Glen Rose Limestone (limestone, marlstone), from the Early Cretaceous, 100 to 145 million years old.
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 23×. 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, marlstone. Age: Early Cretaceous, 100 to 145 million years old. About 13 mi of the line.
Dolostone, limestone. Age: Early Ordovician, 471 to 487 million years old. About 5 mi of the line.
Limestone. Age: Early Cretaceous, 100 to 113 million years old. About 3 mi of the line.
Limestone. Age: Early Cretaceous, 100 to 145 million years old. About 2 mi of the line.
Dolostone, limestone. Age: Early Ordovician, 471 to 487 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.
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 Johnson City reaches the Gulf of America by way of the Pedernales and the Colorado: about 400 river miles.
Lake on the way: Lake Marble Falls.
320 miles of the trip are on the Colorado.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Johnson City; river miles along the main stem, rounded.
