The Merrimac 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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77° on Nov. 11, 2020, the hottest reading for this week of the year since 1899. Next is 75° in 1993.
Merrimac’s center stands about 120 ft above sea level. Within three miles the land runs from 0 ft to 290 ft, a difference of 290 ft: rolling country. The highest named summit within 15 miles is Warner Hill, about 620 ft, 14 miles west-northwest.
Under the town center the state geologic map shows Berwick Formation (metaclastic), from the Silurian, 422 to 445 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 51×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Granofels, biotite-schist. Age: Ordovician to Silurian, 422 to 487 million years old. About 8 mi of the line.
Tonalite, granodiorite. Age: Middle Ordovician to Silurian, 440 to 470 million years old. About 5 mi of the line.
Metaclastic. Age: Silurian, 422 to 445 million years old. About 4 mi of the line.
Phyllite. Age: Silurian, 422 to 445 million years old. About 2 mi of the line.
Granite. Age: Silurian, 422 to 445 million years old. About 1 mi of the line.
Phyllite. Age: Ordovician to Silurian, 422 to 487 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. 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 Merrimac reaches the Atlantic Ocean by way of Cobbler Brook and the Merrimack: about 13 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Merrimac; river miles along the main stem, rounded.
Merrimac has a hot-summer humid continental climate. Summer afternoons average 83° in July; winter nights fall to about 16° in January. A normal year brings about 58 inches of snow; with the rain, that comes to about 50 inches of water.
On November 14 Merrimac normally reaches 51° and falls to 31°. The record high is 74°, in 1989; the record low 11°, in 1986. The most rain on this date, 1.85 in, fell in 1995.
Normals 1991–2020 and records since 1899 at Haverhill, 6 miles south-southwest, 100 ft lower. NOAA, through RCC-ACIS.
