The Petersham 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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74° on Nov. 11, 2020, the hottest reading for this week of the year since 1959. Next is 73° in 1993.
Petersham’s center stands about 1,090 ft above sea level. Within three miles the land runs from 700 ft to 1,210 ft, a difference of 510 ft: hilly country. The highest named summit within 15 miles is Dry Hill, about 1,420 ft, 15 miles west-northwest.
Under the town center the state geologic map shows Hardwick Tonalite (gneiss), from the Early Devonian, 394 to 422 million years old.
The section below crosses 13 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 26×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Gneiss, amphibolite. Age: Late Ordovician to Silurian, 440 to 454 million years old. About 5 mi of the line.
Gneiss. Age: Early Devonian, 394 to 422 million years old. About 5 mi of the line.
Schist, phyllite. Age: Early Devonian, 394 to 422 million years old. About 4 mi of the line.
Mica-schist. Age: Late Ordovician, 449 to 453 million years old. About 3 mi of the line.
Granofels, schist. Age: Neoproterozoic, 542 to 1,000 million years old. About 2 mi of the line.
Biotite-gneiss, amphibolite. Age: Late Ordovician to Silurian, 440 to 454 million years old. About 2 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 7 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 Petersham reaches Long Island Sound and the Atlantic Ocean by way of the East Branch Swift, the Swift, the Chicopee and the Connecticut: about 120 river miles.
80 miles of the trip are on the Connecticut.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Petersham; river miles along the main stem, rounded.
Petersham has a warm-summer humid continental climate. Summer afternoons average 83° in July; winter nights fall to about 13° in January. A normal year brings about 60 inches of snow; with the rain, that comes to about 48 inches of water.
On November 14 Petersham normally reaches 50° and falls to 28°. The record high is 66°, in 1964; the record low 5°, in 1986. The most rain on this date, 0.85 in, fell in 1975.
Normals 1991–2020 and records since 1959 at Barre Falls Dam, 9 miles east-southeast, 260 ft lower. NOAA, through RCC-ACIS.
