The Colonial Beach 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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Colonial Beach’s center stands about 12 ft above sea level. Within three miles the land runs from 0 ft to 60 ft, a difference of 60 ft: gently rolling country. Open water lies within three miles. The highest named summit within 15 miles is Smith Mount Hill, about 240 ft, 9 miles south.
The section below crosses 6 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: Tertiary, 2.6 to 66 million years old. About 3 mi of the line.
Sand, silt. Age: Tertiary, 2.6 to 66 million years old. About 3 mi of the line.
Sand. Age: Quaternary, less than 2.6 million years old. About 3 mi of the line.
Sand, silt, clay. Age: Quaternary, less than 2.6 million years old. About 1 mi of the line.
Fine-detrital, coarse-detrital. Age: Quaternary, less than 2.6 million years old. About 1 mi of the line.
Gravel. Age: Tertiary, 2.6 to 66 million years old. About 0.8 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 Colonial Beach reaches Chesapeake Bay and the Atlantic Ocean by way of Goldman Creek and the Potomac: about 50 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Colonial Beach; river miles along the main stem, rounded.
