The Casco 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.
Casco’s center stands about 730 ft above sea level. Within three miles the land runs from 660 ft to 830 ft, a difference of 170 ft: gently rolling country. The highest named summit within 15 miles is Cherneyville Hill, about 1,020 ft, 11 miles south-southwest.
Under the town center the state geologic map shows Silurian, undivided (dolostone), from the Silurian, 422 to 445 million years old.
The section below crosses 2 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 62×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Dolostone. Age: Silurian, 422 to 445 million years old. About 17 mi of the line.
Shale, dolostone. Age: Ordovician, 445 to 487 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 Casco reaches Lake Michigan by way of Rio Creek, Silver Creek and the Ahnapee: about 14 river miles. From there it moves on through the Great Lakes, over Niagara Falls and down the St. Lawrence to the Atlantic.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Casco; river miles along the main stem, rounded.