The Tacna 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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93° on Nov. 12, 1999, the hottest reading for this week of the year since 1969. Next is 93° in 2025.
Tacna’s center stands about 350 ft above sea level. Within three miles the land runs from 250 ft to 460 ft, a difference of 210 ft: rolling country. The highest named summit within 15 miles is Coyote Peak, about 2,740 ft, 13 miles south-southwest.
Under the town center the state geologic map shows Quaternary surficial deposits, undivided (sand, silt, clay), from the Pleistocene to Holocene, less than 2 million years old.
The section below crosses 2 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 18×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sand, silt, clay. Age: Pleistocene to Holocene, less than 2 million years old. About 23 mi of the line.
Conglomerate, sandstone. Age: Early Oligocene to Late Miocene, 11 to 32 million years old. About 0.8 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale.
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 Tacna reaches the Gulf of California by way of the Gila and the Colorado: about 170 river miles.
120 miles of the trip are on the Colorado.
Often dry. About 50% of the way is mapped as streams that run only after rain or snowmelt; the water makes the whole trip in floods.
Seldom reaches the sea. Dams and canals now take nearly all of the Colorado before its old delta in Mexico.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Tacna; river miles along the main stem, rounded.
Tacna has a hot desert climate. Summer afternoons average 109° in July; winter nights fall to about 36° in December. About 4 inches of rain fall in a normal year.
On November 14 Tacna normally reaches 80° and falls to 44°. The record high is 92°, in 2025; the record low 28°, in 1975. The most rain on this date, 0.07 in, fell in 1993.
Normals 1991–2020 and records since 1969 at Tacna 3 NE, 3 miles northeast. NOAA, through RCC-ACIS.
