The Andover 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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3.51 inches of rain fell in two days, the most for this week of the year since records began in 1893. The next wettest, 3.04 inches, fell in 1975.
Andover’s center stands about 190 ft above sea level. Within three miles the land runs from 50 ft to 360 ft, a difference of 310 ft: rolling country. The highest named summit within 15 miles is Jeremy Hill, about 600 ft, 13 miles west-northwest.
Under the town center the state geologic map shows Andover Granite (granite, pegmatite), from the Ordovician to Silurian, 422 to 487 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 53×. 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, pegmatite. Age: Ordovician to Silurian, 422 to 487 million years old. About 6 mi of the line.
Tonalite, diorite. Age: Silurian, 425 to 435 million years old. About 5 mi of the line.
Metaclastic. Age: Silurian, 422 to 445 million years old. About 3 mi of the line.
Diorite, gabbro. Age: Neoproterozoic, 542 to 1,000 million years old. About 2 mi of the line.
Granofels, biotite-schist. Age: Ordovician to Silurian, 422 to 487 million years old. About 2 mi of the line.
Diorite, tonalite. Age: Silurian to Devonian, 359 to 445 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 Andover reaches the Atlantic Ocean by way of the Shawsheen and the Merrimack: about 35 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Andover; river miles along the main stem, rounded.
Andover has a hot-summer humid continental climate. Summer afternoons average 83° in July; winter nights fall to about 20° in January. About 49 inches of rain fall in a normal year.
On November 14 Andover normally reaches 51° and falls to 35°. The record high is 70°, in 1959; the record low 12°, in 1905. The most rain on this date, 2.75 in, fell in 1937.
Normals 1991–2020 and records since 1893 at Lawrence, 3 miles north-northwest, 140 ft lower. NOAA, through RCC-ACIS.
