The Acton 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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76° on Nov. 12, 2022, the hottest reading for this week of the year since 1949. Next is 75° in 2020.
Acton’s center stands about 260 ft above sea level. Within three miles the land runs from 130 ft to 370 ft, a difference of 240 ft: rolling country. The highest named summit within 15 miles is Mount Pisgah, about 750 ft, 14 miles southwest.
Under the town center the state geologic map shows Nashoba Formation (schist, gneiss), from the Neoproterozoic to Ordovician, 445 to 1,000 million years old.
The section below crosses 7 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 34×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Schist, gneiss. Age: Neoproterozoic to Ordovician, 445 to 1,000 million years old. About 16 mi of the line.
Amphibolite. Age: Neoproterozoic to Ordovician, 445 to 1,000 million years old. About 4 mi of the line.
Granite, pegmatite. Age: Ordovician to Silurian, 422 to 487 million years old. About 2 mi of the line.
Gneiss. Age: Early Cambrian to Early Ordovician, 478 to 523 million years old. About 0.9 mi of the line.
Granite. Age: Silurian, 428 to 438 million years old. About 0.8 mi of the line.
Phyllite, schist. Age: Neoproterozoic to Silurian, 422 to 1,000 million years old. About 0.6 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 1 smaller unit 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 Acton reaches the Atlantic Ocean by way of Nashoba Brook, Fort Pond Brook, the Assabet, the Concord and the Merrimack: about 65 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Acton; river miles along the main stem, rounded.
Acton has a hot-summer humid continental climate. Summer afternoons average 85° in July; winter nights fall to about 18° in January. About 43 inches of rain fall in a normal year.
On November 14 Acton normally reaches 53° and falls to 33°. The record high is 70°, in 1959; the record low 14°, in 2019. The most rain on this date, 3.12 in, fell in 2009.
Normals 1991–2020 and records since 1949 at Bedford Hanscom Field, 7 miles east, 130 ft lower. NOAA, through RCC-ACIS.
