The Merrifield 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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76° on Nov. 12, 2014, the hottest reading for this week of the year since 1925. Next is 75° in 2020.
Merrifield’s center stands about 370 ft above sea level. Within three miles the land runs from 250 ft to 490 ft, a difference of 240 ft: rolling country.
Under the town center the state geologic map shows Sykesville Formation (melange), from the Cambrian, 487 to 542 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 37×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Schist. Age: Neoproterozoic to Cambrian, 487 to 1,000 million years old. About 4 mi of the line.
Tonalite. Age: Cambrian to Ordovician, 445 to 542 million years old. About 3 mi of the line.
Sandstone. Age: Triassic, 202 to 252 million years old. About 2 mi of the line.
Melange. Age: Cambrian, 487 to 542 million years old. About 2 mi of the line.
Gravel, sand. Age: Pliocene, 2.6 to 5.3 million years old. About 2 mi of the line.
Fine-detrital, coarse-detrital. Age: Pleistocene, less than 2.6 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. 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 Merrifield reaches Chesapeake Bay and the Atlantic Ocean by way of Long Branch, Accotink Creek and the Potomac: about 120 river miles.
95 miles of the trip are on the Potomac.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Merrifield; river miles along the main stem, rounded.
Merrifield has a humid subtropical climate. Summer afternoons average 84° in July; winter nights fall to about 23° in January. A normal year brings about 18 inches of snow; with the rain, that comes to about 44 inches of water.
On November 14 Merrifield normally reaches 56° and falls to 35°. The record high is 65°, in 2005; the record low 22°, in 2019. The most rain on this date, 1.53 in, fell in 1972.
Normals 1991–2020 and records since 1925 at Vienna, 4 miles west-northwest. NOAA, through RCC-ACIS.
