The Top-of-the-World 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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Top-of-the-World’s center stands about 4,650 ft above sea level. Within three miles the land runs from 3,570 ft to 5,310 ft, a difference of 1,740 ft: steep hill country. The highest named summit within 15 miles is Pinal Peak, about 7,820 ft, 11 miles east-southeast.
Under the town center the state geologic map shows Middle Miocene to Oligocene volcanic rocks (basalt, andesite, dacite), from the Middle Eocene to Late Miocene, 11 to 38 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 5×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Metasedimentary, schist. Age: Paleoproterozoic, 1.6 to 1.8 billion years old. About 8 mi of the line.
Granite, granodiorite, tonalite. Age: Paleoproterozoic, 1.6 to 1.8 billion years old. About 5 mi of the line.
Basalt, andesite, dacite. Age: Middle Eocene to Late Miocene, 11 to 38 million years old. About 5 mi of the line.
Granite, granodiorite, diorite. Age: Late Cretaceous to Early Eocene, 50 to 82 million years old. About 3 mi of the line.
Granite. Age: Mesoproterozoic, 1.4 to 1.4 billion years old. About 2 mi of the line.
Shale, sandstone, quartzite. Age: Mesoproterozoic to Neoproterozoic, 700 to 1,300 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. 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 Top-of-the-World reaches the Gulf of California by way of Mineral Creek, the Gila and the Colorado: about 460 river miles.
310 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 Top-of-the-World; river miles along the main stem, rounded.
