The Somerville 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 1915. Next is 75° in 1971.
Somerville’s center stands about 780 ft above sea level. Within three miles the land runs from 720 ft to 1,060 ft, a difference of 340 ft: rolling country. The highest named summit within 15 miles is Mount Auburn, about 960 ft, 5 miles north-northwest.
Under the town center the state geologic map shows Waynesville and Arnheim Formations, Undivided (shale, limestone), from the Late Ordovician, 445 to 454 million years old.
The section below crosses 6 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 31×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Shale, limestone. Age: Late Ordovician, 445 to 454 million years old. About 7 mi of the line.
Shale, limestone. Age: Late Ordovician, 445 to 459 million years old. About 6 mi of the line.
Shale, limestone. Age: Late Ordovician, 445 to 454 million years old. About 5 mi of the line.
Shale. Age: Middle Ordovician to Late Ordovician, 445 to 471 million years old. About 2 mi of the line.
Dolostone, limestone, shale. Age: Silurian, 422 to 445 million years old. About 2 mi of the line.
Dolostone. Age: Silurian, 425 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.
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 Somerville reaches the Gulf of America by way of Sevenmile Creek, Four Mile Creek, the Great Miami, the Ohio and the Mississippi: about 1,510 river miles.
970 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Somerville; river miles along the main stem, rounded.
Somerville has a hot-summer humid continental climate. Summer afternoons average 85° in July; winter nights fall to about 17° in January. About 43 inches of rain fall in a normal year.
On November 14 Somerville normally reaches 53° and falls to 31°. The record high is 72°, in 1958; the record low 4°, in 2019. The most rain on this date, 1.70 in, fell in 1972.
Normals 1991–2020 and records since 1915 at Eaton, 12 miles north, 220 ft higher. NOAA, through RCC-ACIS.
