The Ak Chin 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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Ak Chin’s center stands about 1,850 ft above sea level. Within three miles the land runs from 1,770 ft to 1,940 ft, a difference of 170 ft: gently rolling country. The highest named summit within 15 miles is Gu Achi Peak, about 4,530 ft, 9 miles east-northeast.
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 5 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.
Sand, silt, clay. Age: Pleistocene to Holocene, less than 2 million years old. About 12 mi of the line.
Arenite, conglomerate. Age: Late Jurassic to Late Cretaceous, 80 to 160 million years old. About 9 mi of the line.
Silt, clay. Age: Holocene, less than 10,000 years old. About 3 mi of the line.
Conglomerate, sandstone. Age: Early Oligocene to Late Miocene, 11 to 32 million years old. About 0.7 mi of the line.
Diorite, alkali-granite, granodiorite. Age: Early Jurassic to Late Jurassic, 150 to 180 million years old. About 0.4 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 Ak Chin reaches the Gulf of California by way of Santa Rosa Wash, the Gila and the Colorado: about 420 river miles.
220 miles of the trip are on the Gila.
Often dry. About 70% 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 Ak Chin; river miles along the main stem, rounded.
