The Gilbert 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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87° on Nov. 11, 1989, the hottest reading for this week of the year since 1924. Next is 85° in 1999.
Gilbert’s center stands about 660 ft above sea level. Within three miles the land runs from 570 ft to 970 ft, a difference of 400 ft: hilly country. The highest named summit within 15 miles is Horn Mountain, about 2,210 ft, 14 miles west-southwest.
The section below crosses 8 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 13×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Limestone. Age: Carboniferous, 324 to 359 million years old. About 13 mi of the line.
Limestone. Age: Middle Ordovician to Late Ordovician, 445 to 471 million years old. About 3 mi of the line.
Shale. Age: Carboniferous, 299 to 324 million years old. About 2 mi of the line.
Sandstone, dolostone. Age: Middle Ordovician, 459 to 471 million years old. About 2 mi of the line.
Sandstone, shale, limestone. Age: Carboniferous, 324 to 359 million years old. About 2 mi of the line.
Shale, sandstone. Age: Carboniferous, 299 to 324 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. 2 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 Gilbert reaches the Gulf of America by way of the Buffalo, the White River and the Mississippi: about 1,050 river miles.
620 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Gilbert; river miles along the main stem, rounded.
Gilbert has a humid subtropical climate. Summer afternoons average 90° in August; winter nights fall to about 24° in January. About 48 inches of rain fall in a normal year, with about 4 inches of snow.
On November 14 Gilbert normally reaches 61° and falls to 35°. The record high is 83°, in 1999; the record low 5°, in 1940. The most rain on this date, 2.15 in, fell in 1926.
Normals 1991–2020 and records since 1924 at Gilbert, here. NOAA, through RCC-ACIS.
