The Machias 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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Machias’s center stands about 90 ft above sea level. Within three miles the land runs from 0 ft to 340 ft, a difference of 340 ft: rolling country. The highest named summit within 15 miles is Peaked Mountain, about 540 ft, 12 miles west-northwest.
Under the town center the state geologic map shows Silurian Dennys Formation, mafic to felsic volcanic rock member (mafic-volcanic, felsic-volcanic), from the Silurian, 422 to 445 million years old.
The section below crosses 10 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 49×. 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: Devonian, 359 to 422 million years old. About 8 mi of the line.
Age: Devonian, 359 to 422 million years old. About 3 mi of the line.
Mafic-volcanic, felsic-volcanic. Age: Silurian, 422 to 445 million years old. About 3 mi of the line.
Shale. Age: Silurian, 422 to 445 million years old. About 2 mi of the line.
Gabbro, diorite, ultramafic. Age: Devonian, 359 to 422 million years old. About 2 mi of the line.
Basalt. Age: Devonian, 359 to 422 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. 4 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.
Rain that falls on Machias runs straight into the Atlantic Ocean.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Machias; river miles along the main stem, rounded.
