The Saybrook 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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Saybrook’s center stands about 810 ft above sea level. Within three miles the land runs from 750 ft to 900 ft, a difference of 150 ft: gently rolling country.
Under the town center the state geologic map shows Bond Formation (shale, sandstone, limestone), from the Late Pennsylvanian, 304 to 307 million years old.
The section below crosses 7 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.
Shale, sandstone, limestone. Age: Late Pennsylvanian, 304 to 307 million years old. About 9 mi of the line.
Shale, limestone. Age: Late Pennsylvanian, 304 to 307 million years old. About 6 mi of the line.
Shale. Age: Late Pennsylvanian, 304 to 307 million years old. About 5 mi of the line.
Shale, sandstone. Age: Early Pennsylvanian to Middle Pennsylvanian, 307 to 324 million years old. About 2 mi of the line.
Limestone. Age: Middle Devonian, 384 to 394 million years old. About 1 mi of the line.
Shale. Age: Middle Devonian to Late Devonian, 359 to 388 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. 1 smaller unit along the line are not listed.
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 Saybrook reaches the Gulf of America by way of the Sangamon, the Illinois and the Mississippi: about 1,500 river miles.
1,190 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Saybrook; river miles along the main stem, rounded.
