The Hillsboro 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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Hillsboro’s center stands about 440 ft above sea level. Within three miles the land runs from 390 ft to 520 ft, a difference of 130 ft: gently rolling country. The highest named summit within 15 miles is Sherman Hill, about 640 ft, 15 miles south-southeast.
Under the town center the state geologic map shows Cockfield (clay, sand), from the Eocene, 34 to 56 million years old.
The section below crosses 4 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.
Clay. Age: Eocene, 34 to 56 million years old. About 12 mi of the line.
Clay, sand. Age: Eocene, 34 to 56 million years old. About 8 mi of the line.
Marl, sand. Age: Eocene, 34 to 56 million years old. About 3 mi of the line.
Sand, clay. Age: Eocene, 34 to 56 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.
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 Hillsboro reaches the Gulf of America by way of the Tallabogue, Tuscolameta Creek and the Pearl: about 390 river miles.
Lake on the way: Cypress Lake.
310 miles of the trip are on the Pearl.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Hillsboro; river miles along the main stem, rounded.
