The Andover 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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Andover’s center stands about 710 ft above sea level. Within three miles the land runs from 650 ft to 2,020 ft, a difference of 1,370 ft: steep hill country. The highest named summit within 15 miles is Old Speck Mountain, about 4,180 ft, 11 miles west-southwest.
Under the town center the state geologic map shows Devonian tonalite, from the Devonian, 359 to 422 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 6×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Granite, tonalite. Age: Devonian, 359 to 422 million years old. About 11 mi of the line.
Tonalite. Age: Devonian, 359 to 422 million years old. About 4 mi of the line.
Mudstone, sandstone. Age: Silurian, 428 to 445 million years old. About 3 mi of the line.
Mudstone, sandstone. Age: Early Devonian, 410 to 414 million years old. About 2 mi of the line.
Schist. Age: Devonian, 359 to 422 million years old. About 2 mi of the line.
Sandstone, shale. Age: Silurian, 422 to 445 million years old. About 0.9 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 Andover reaches the Atlantic Ocean by way of Gardner Brook, the Ellis, the Androscoggin and the Kennebec: about 130 river miles.
100 miles of the trip are on the Androscoggin.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Andover; river miles along the main stem, rounded.
