The Bel Air 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 1919. Next is 77° in 1955.
Bel Air’s center stands about 380 ft above sea level. Within three miles the land runs from 220 ft to 490 ft, a difference of 270 ft: rolling country.
Under the town center the state geologic map shows Baltimore Gabbro Complex, from the Proterozoic to Paleozoic, 252 to 2,500 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 26×. 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-gneiss. Age: Proterozoic, 542 to 2,500 million years old. About 5 mi of the line.
Sand. Age: Cretaceous, 66 to 145 million years old. About 5 mi of the line.
Gneiss, quartz-diorite, granodiorite. Age: Neoproterozoic to Middle Cambrian, 500 to 600 million years old. About 4 mi of the line.
Gabbro. Age: Proterozoic to Paleozoic, 252 to 2,500 million years old. About 3 mi of the line.
Metagraywacke, muscovite-schist. Age: Proterozoic, 542 to 2,500 million years old. About 2 mi of the line.
Fine-detrital, coarse-detrital. Age: Pleistocene, less than 2.6 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.
A raindrop that lands in Bel Air reaches Chesapeake Bay and the Atlantic Ocean by way of Bynum Run, Bush Creek and the Bush: about 18 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Bel Air; river miles along the main stem, rounded.
Bel Air has a humid subtropical climate. Summer afternoons average 86° in July; winter nights fall to about 25° in January. About 47 inches of rain fall in a normal year.
On November 14 Bel Air normally reaches 56° and falls to 37°. The record high is 77°, in 1955; the record low 21°, in 1986. The most rain on this date, 1.83 in, fell in 1972.
Normals 1991–2020 and records since 1919 at Aberdeen Phillips Field, 10 miles east-southeast, 320 ft lower. NOAA, through RCC-ACIS.
