The Tappan 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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80° on Nov. 15, 1993, the hottest reading for this week of the year since 1939. Next is 74° in 1949.
Tappan’s center stands about 110 ft above sea level. Within three miles the land runs from 0 ft to 590 ft, a difference of 590 ft: hilly country. Open water lies within three miles. The highest named summit within 15 miles is Breakneck Mountain, about 1,290 ft, 14 miles north-northwest.
Under the town center the state geologic map shows Brunswick Formation (mudstone, sandstone, arkose), from the Late Triassic, 202 to 237 million years old.
The section below crosses 5 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 32×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sandstone, siltstone. Age: Early Jurassic to Late Jurassic, 145 to 202 million years old. About 12 mi of the line.
Mudstone, sandstone, arkose. Age: Late Triassic, 202 to 237 million years old. About 3 mi of the line.
Basalt. Age: Early Jurassic, 175 to 202 million years old. About 2 mi of the line.
Marble. Age: Early Cambrian to Early Ordovician, 471 to 542 million years old. About 0.6 mi of the line.
Pelitic-schist, gneiss, amphibolite. Age: Early Cambrian to Middle Ordovician, 459 to 542 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.
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 Tappan reaches New York Harbor and the Atlantic Ocean by way of Sparkill Creek and the Hudson: about 30 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Tappan; river miles along the main stem, rounded.
Tappan has a humid subtropical climate. Summer afternoons average 86° in July; winter nights fall to about 29° in January. A normal year brings about 30 inches of snow; with the rain, that comes to about 45 inches of water.
On November 14 Tappan normally reaches 56° and falls to 44°. The record high is 72°, in 1993; the record low 24°, in 1986. The most rain on this date, 2.05 in, fell in 1972.
Normals 1991–2020 and records since 1939 from the New York-LGA Area threaded record (Laguardia Airport, 17 miles south-southeast, 100 ft lower). NOAA, through RCC-ACIS.
