The Ellicott City 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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82° on Nov. 15, 1993, the hottest reading for this week of the year since 1950. Next is 80° in 1973.
Ellicott City’s center stands about 210 ft above sea level. Within three miles the land runs from 170 ft to 530 ft, a difference of 360 ft: rolling country. The highest named summit within 15 miles is Chestnut Hill, about 610 ft, 2 miles north.
Under the town center the state geologic map shows Ellicott City Granodiorite (quartz-monzonite), from the Middle Ordovician to Late Devonian, 370 to 470 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 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.
Biotite-schist. Age: Proterozoic, 542 to 2,500 million years old. About 5 mi of the line.
Gabbro. Age: Proterozoic to Paleozoic, 252 to 2,500 million years old. About 4 mi of the line.
Sand. Age: Cretaceous, 66 to 145 million years old. About 4 mi of the line.
Gneiss. Age: Precambrian. About 4 mi of the line.
Quartz-monzonite. Age: Middle Ordovician to Late Devonian, 370 to 470 million years old. About 2 mi of the line.
Muscovite-gneiss. Age: Proterozoic, 542 to 2,500 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 Ellicott City reaches Chesapeake Bay and the Atlantic Ocean by way of Plumtree Branch, the Little Patuxent and the Patuxent: about 95 river miles.
65 miles of the trip are on the Patuxent.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Ellicott City; river miles along the main stem, rounded.
Ellicott City has a humid subtropical climate. Summer afternoons average 90° in July; winter nights fall to about 30° in January. About 44 inches of rain fall in a normal year.
On November 14 Ellicott City normally reaches 58° and falls to 43°. The record high is 78°, in 1989; the record low 21°, in 1986. The most rain on this date, 2.46 in, fell in 1972.
Normals 1991–2020 and records since 1950 from the Baltimore Downtown Area threaded record (Maryland Science Center, 10 miles east, 190 ft lower). NOAA, through RCC-ACIS.
