The Derwood 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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16° on Nov. 16, 1996, the coldest reading for this week of the year since 1993. Next is 18° in 2017.
Derwood’s center stands about 480 ft above sea level. Within three miles the land runs from 320 ft to 540 ft, a difference of 220 ft: rolling country.
Under the town center the state geologic map shows Wissahickon Formation (Undivided) (muscovite-schist), from the Proterozoic, 542 to 2,500 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 30×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Muscovite-schist. Age: Proterozoic, 542 to 2,500 million years old. About 17 mi of the line.
Muscovite-gneiss. Age: Proterozoic, 542 to 2,500 million years old. About 3 mi of the line.
Phyllite. Age: Proterozoic, 542 to 2,500 million years old. About 2 mi of the line.
Melange. Age: Cambrian, 487 to 542 million years old. About 2 mi of the line.
Serpentinite. Age: Proterozoic to Paleozoic, 252 to 2,500 million years old. About 0.9 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 Derwood reaches Chesapeake Bay and the Atlantic Ocean by way of Crabbs Branch, Rock Creek and the Potomac: about 140 river miles.
110 miles of the trip are on the Potomac.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Derwood; river miles along the main stem, rounded.
Derwood has a hot-summer humid continental climate. Summer afternoons average 84° in July; winter nights fall to about 25° in January. A normal year brings about 31 inches of snow; with the rain, that comes to about 48 inches of water.
On November 14 Derwood normally reaches 54° and falls to 37°. The record high is 74°, in 1993; the record low 22°, in 2019. The most rain on this date, 1.90 in, fell in 1995.
Normals 1991–2020 and records since 1993 at Damascus 3 SSW, 11 miles north-northwest, 220 ft higher. NOAA, through RCC-ACIS.
