The Chapman 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. 15, 1993, the hottest reading for this week of the year since 1912. Next is 74° in 1973.
Chapman’s center stands about 670 ft above sea level. Within three miles the land runs from 420 ft to 920 ft, a difference of 500 ft: hilly country. The highest named summit within 15 miles is Call Mountain, about 1,570 ft, 15 miles northwest.
Under the town center the state geologic map shows Martinsburg Formation (shale, slate), from the Ordovician, 445 to 487 million years old.
The section below crosses 17 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 14×. 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, slate. Age: Ordovician, 445 to 487 million years old. About 5 mi of the line.
Limestone, dolostone. Age: Ordovician, 445 to 487 million years old. About 3 mi of the line.
Shale, siltstone. Age: Early Devonian to Middle Devonian, 384 to 422 million years old. About 3 mi of the line.
Dolostone, limestone. Age: Cambrian, 487 to 542 million years old. About 2 mi of the line.
Shale. Age: Ordovician, 445 to 487 million years old. About 2 mi of the line.
Dolostone. Age: Cambrian, 487 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. 11 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 Chapman reaches Delaware Bay and the Atlantic Ocean by way of Monocacy Creek, the Lehigh and the Delaware: about 180 river miles.
150 miles of the trip are on the Delaware.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Chapman; river miles along the main stem, rounded.
Chapman has a hot-summer humid continental climate. Summer afternoons average 86° in July; winter nights fall to about 22° in January. A normal year brings about 33 inches of snow; with the rain, that comes to about 47 inches of water.
On November 14 Chapman normally reaches 54° and falls to 34°. The record high is 73°, in 1993; the record low 17°, in 1986. The most rain on this date, 2.41 in, fell in 1972.
Normals 1991–2020 and records since 1912 from the Allentown Area threaded record (Allentown Lehigh Valley International Airport, 8 miles south-southwest, 280 ft lower). NOAA, through RCC-ACIS.
