The Thornton 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.
Mostly cloudy
Partly cloudy
Partly cloudy
Mostly sunny
Partly cloudy
Partly cloudy
Partly cloudy
Thornton’s center stands about 1,250 ft above sea level. Within three miles the land runs from 590 ft to 2,650 ft, a difference of 2,060 ft: mountain country. The highest named summit within 15 miles is Mount Lafayette, about 5,200 ft, 15 miles north.
Under the town center the state geologic map shows Kinsman Granodiorite, from the Early Devonian, 394 to 422 million years old.
The section below crosses 8 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 5×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Granodiorite. Age: Early Devonian, 394 to 422 million years old. About 7 mi of the line.
Granite. Age: Middle Jurassic to Late Jurassic, 145 to 175 million years old. About 5 mi of the line.
Pelitic-schist, metasandstone. Age: Silurian, 434 to 445 million years old. About 4 mi of the line.
Metaclastic. Age: Silurian, 434 to 445 million years old. About 3 mi of the line.
Metasedimentary. Age: Early Devonian, 394 to 422 million years old. About 3 mi of the line.
Quartzite, metasedimentary. Age: Silurian, 422 to 445 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. 2 smaller units 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 Thornton reaches the Atlantic Ocean by way of the Pemigewasset and the Merrimack: about 160 river miles.
120 miles of the trip are on the Merrimack.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Thornton; river miles along the main stem, rounded.
