The Fort Johnson 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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Fort Johnson’s center stands about 370 ft above sea level. Within three miles the land runs from 260 ft to 840 ft, a difference of 580 ft: hilly country. The highest named summit within 15 miles is Bernhardt Mountain, about 2,310 ft, 14 miles north-northwest.
Under the town center the state geologic map shows Canajoharie Shale (black-shale), from the Middle Ordovician, 459 to 471 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 11×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Black-shale. Age: Middle Ordovician, 459 to 471 million years old. About 15 mi of the line.
Graywacke, sandstone, siltstone. Age: Late Ordovician, 445 to 459 million years old. About 4 mi of the line.
Unconsolidated. Age: Quaternary, less than 2.6 million years old. About 3 mi of the line.
Quartzite, schist. Age: Mesoproterozoic, 1 to 1.6 billion 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 Fort Johnson reaches New York Harbor and the Atlantic Ocean by way of the Mohawk and the Hudson: about 200 river miles.
160 miles of the trip are on the Hudson.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Fort Johnson; river miles along the main stem, rounded.
