The Franconia 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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Franconia’s center stands about 3,180 ft above sea level. Within three miles the land runs from 1,850 ft to 4,800 ft, a difference of 2,950 ft: mountain country. The highest named summit within 15 miles is Mount Lafayette, about 5,200 ft, 2 miles southwest.
Under the town center the state geologic map shows Porphyritic hornblende or alkalic amphibole quartz syenite (quartz-syenite), from the Jurassic, 145 to 202 million years old.
The section below crosses 9 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.
Granite. Age: Middle Jurassic to Late Jurassic, 145 to 175 million years old. About 9 mi of the line.
Granodiorite. Age: Early Devonian, 394 to 422 million years old. About 4 mi of the line.
Granodiorite. Age: Early Devonian, 394 to 422 million years old. About 3 mi of the line.
Granitic. Age: Early Jurassic, 175 to 202 million years old. About 3 mi of the line.
Felsic-volcanic, mafic-volcanic. Age: Middle Ordovician to Late Ordovician, 445 to 471 million years old. About 1 mi of the line.
Granodiorite. Age: Late Ordovician, 445 to 459 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. 3 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 Franconia reaches the Atlantic Ocean by way of Franconia Branch, the East Branch Pemigewasset, the Pemigewasset and the Merrimack: about 180 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 Franconia; river miles along the main stem, rounded.
