The Thetford 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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Partly cloudy; warmer
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72° on Nov. 11, 2020, the hottest reading for this week of the year since 1950. Next is 70° in 2022.
Thetford’s center stands about 570 ft above sea level. Within three miles the land runs from 480 ft to 1,490 ft, a difference of 1,010 ft: steep hill country. The highest named summit within 15 miles is Smarts Mountain, about 3,220 ft, 11 miles east.
Under the town center the state geologic map shows Gile Mountain Formation - thick-bedded micaceous feldspathic quartzite member (mica-schist, quartzite), from the Early Devonian, 394 to 422 million years old.
The section below crosses 12 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 8×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Mica-schist, quartzite. Age: Early Devonian, 394 to 422 million years old. About 7 mi of the line.
Phyllite, limestone. Age: Silurian to Early Devonian, 394 to 425 million years old. About 6 mi of the line.
Felsic-volcanic, mafic-volcanic. Age: Middle Ordovician to Late Ordovician, 445 to 471 million years old. About 3 mi of the line.
Granodiorite. Age: Early Devonian, 394 to 422 million years old. About 2 mi of the line.
Quartzite. Age: Early Devonian, 394 to 422 million years old. About 1 mi of the line.
Metaandesite, metabasalt. Age: Middle Ordovician to Late Ordovician, 445 to 471 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. 6 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 Thetford reaches Long Island Sound and the Atlantic Ocean by way of the Ompompanoosuc and the Connecticut: about 230 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Thetford; river miles along the main stem, rounded.
Thetford has a warm-summer humid continental climate. Summer afternoons average 82° in July; winter nights fall to about 6° in January. About 40 inches of rain fall in a normal year.
Normals 1991–2020 and records since 1950 at Union Village Dam, 3 miles south, 110 ft lower. NOAA, through RCC-ACIS.
