The Marion 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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Mostly cloudy; cooler
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21° on Nov. 14, 2018, the coldest reading for this week of the year since 1948. Next is 25° in 1969.
Marion’s center stands about 650 ft above sea level. Within three miles the land runs from 580 ft to 750 ft, a difference of 170 ft: gently rolling country. The highest named summit within 15 miles is Mission Hill, about 970 ft, 10 miles north.
Under the town center the state geologic map shows Leona Formation (coarse-detrital, fine-detrital), from the Pleistocene, less than 2.6 million years old.
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 34×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Mudstone. Age: Late Paleocene to Early Eocene, 48 to 59 million years old. About 7 mi of the line.
Coarse-detrital, fine-detrital. Age: Pleistocene, less than 2.6 million years old. About 5 mi of the line.
Limestone, carbonate. Age: Late Cretaceous, 66 to 72 million years old. About 4 mi of the line.
Clay, siltstone-mudstone. Age: Late Cretaceous, 66 to 100 million years old. About 3 mi of the line.
Limestone. Age: Early Cretaceous, 100 to 113 million years old. About 3 mi of the line.
Limestone. Age: Late Cretaceous, 66 to 100 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 Marion reaches the Gulf of America by way of Santa Clara Creek, Cibolo Creek, the San Antonio, the Guadalupe and the South Guadalupe: about 210 river miles.
130 miles of the trip are on the San Antonio.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Marion; river miles along the main stem, rounded.
Marion has a hot desert climate. Summer afternoons average 96° in July; winter nights fall to about 41° in January. Barely 0.0 inches of rain fall in a normal year.
Normals 1991–2020 and records since 1948 at Randolph Afb, 8 miles west-southwest. NOAA, through RCC-ACIS.
