The Mamaroneck 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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17° on Nov. 15, 1996, the coldest reading for this week of the year since 1946. Next is 18° in 1967.
Mamaroneck’s center stands about 30 ft above sea level. Within three miles the land runs from 0 ft to 260 ft, a difference of 260 ft: rolling country. Open water lies within three miles. The highest named summit within 15 miles is Buttermilk Hill, about 740 ft, 12 miles north-northwest.
Under the town center the state geologic map shows Hartland Formation (amphibolite, pelitic-schist), from the Cambrian to Early Ordovician, 471 to 542 million years old.
The section below crosses 10 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 40×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Clay, sand, gravel. Age: Late Cretaceous, 66 to 100 million years old. About 5 mi of the line.
Pelitic-schist, gneiss, amphibolite. Age: Early Cambrian to Middle Ordovician, 459 to 542 million years old. About 2 mi of the line.
Gneiss. Age: Precambrian to Mesoproterozoic. About 2 mi of the line.
Amphibolite, pelitic-schist. Age: Cambrian to Early Ordovician, 471 to 542 million years old. About 1 mi of the line.
Gneiss. Age: Neoproterozoic to Early Cambrian, 528 to 598 million years old. About 1 mi of the line.
Marble. Age: Early Cambrian to Early Ordovician, 471 to 542 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. 4 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.
Rain that falls on Mamaroneck runs straight into Long Island Sound and the Atlantic Ocean.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Mamaroneck; river miles along the main stem, rounded.
Mamaroneck has a hot-summer humid continental climate. Summer afternoons average 83° in July; winter nights fall to about 23° in January. About 48 inches of rain fall in a normal year.
On November 14 Mamaroneck normally reaches 53° and falls to 37°. The record high is 71°, in 1993; the record low 20°, in 1986. The most rain on this date, 1.92 in, fell in 1972.
Normals 1991–2020 and records since 1946 at Westchester Co Airport, 8 miles north, 340 ft higher. NOAA, through RCC-ACIS.
