The Island Falls 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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Island Falls’s center stands about 460 ft above sea level. Within three miles the land runs from 430 ft to 900 ft, a difference of 470 ft: hilly country. The highest named summit within 15 miles is Mount Chase, about 2,430 ft, 12 miles northwest.
Under the town center the state geologic map shows Silurian undifferentiated pelites and sandstones (slate, sandstone), from the Silurian, 422 to 445 million years old.
The section below crosses 6 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 18×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Quartzite, calc-silicate-rock. Age: Silurian to Devonian, 359 to 445 million years old. About 9 mi of the line.
Slate, sandstone. Age: Silurian, 422 to 445 million years old. About 8 mi of the line.
Mudstone, sandstone. Age: Ordovician to Silurian, 422 to 487 million years old. About 3 mi of the line.
Limestone. Age: Silurian, 422 to 445 million years old. About 2 mi of the line.
Mafic-volcanic, felsic-volcanic. Age: Ordovician, 445 to 487 million years old. About 2 mi of the line.
Conglomerate, sandstone. Age: Silurian, 422 to 445 million years old. About 0.3 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 Island Falls reaches the Atlantic Ocean by way of the West Branch Mattawamkeag, the Mattawamkeag and the Penobscot: about 160 river miles.
Lake on the way: Upper Mattawamkeag Lake.
85 miles of the trip are on the Penobscot.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Island Falls; river miles along the main stem, rounded.
