AZArizona Geography

Arizona does not change its clocks, with one exception, and that exception has a hole in it. The state has ignored daylight saving since 1968. The Navajo Nation, which covers the northeast corner, does observe it. The Hopi Reservation sits entirely surrounded by the Navajo Nation and does not. Drive State Route 264 east from Tuba City on a July morning and the effective local time shifts more than once in under a hundred miles without you ever leaving Arizona.

Three Arizonas stacked from northeast to southwest

The northeastern two fifths of the state is Colorado Plateau: flat lying sedimentary rock at 5,000 to 8,000 feet, sliced by canyons, cold enough in winter to hold snow. The southwestern half is Basin and Range, where isolated fault block mountains rise abruptly out of broad desert basins that are still filling with their own eroded debris. Between them runs the Transition Zone, marked by the Mogollon Rim, an escarpment stretching roughly 200 miles from near Sedona northeast into New Mexico and dropping as much as 2,000 feet in places.

The highest ground is Humphreys Peak at 12,633 feet, the tallest of the San Francisco Peaks outside Flagstaff and the eroded remnant of a stratovolcano whose summit collapsed. The lowest is the Colorado River near Yuma at about 70 feet. Along the Rim near Flagstaff grows what is generally called the largest continuous stand of ponderosa pine in the world. Flagstaff sits at about 7,000 feet and averages roughly 100 inches of snow a year. Phoenix is 145 road miles south at about 1,100 feet and effectively never sees any.

128 degrees above and 40 below

Lake Havasu City recorded 128 degrees on June 29, 1994. Hawley Lake, up on the White Mountains at over 8,000 feet, recorded 40 below zero on January 7, 1971. That is a 168 degree spread inside one state, and both records are products of the same elevation range that stacks pine forest above saguaro desert.

Phoenix ran 31 consecutive days at or above 110 degrees in July 2023. Yuma, at the other corner, receives roughly 90 percent of its possible sunshine, the highest figure of any reporting station in the country. The North American Monsoon flips the wind direction in mid June and delivers a large share of southern Arizona's annual rain in violent afternoon storms through September, which is why Tucson can be greener in August than in April.

What the Colorado River had to cut through

The Grand Canyon runs 277 river miles, opens as wide as 18 miles rim to rim, and drops about a mile from the North Rim to the water. The rock at the bottom, the Vishnu Schist, is close to 1.8 billion years old, while the canyon itself is young: most of the cutting has happened in the last five or six million years. The river reaches the state at Lees Ferry, the point where Colorado River water rights between the upper and lower basin states are measured.

Downstream the Colorado becomes the western border, running roughly 235 miles against Nevada and California. Two other holes in the ground nearby are worth naming. Meteor Crater east of Flagstaff is about 3,900 feet across and 560 feet deep, punched out roughly 50,000 years ago and preserved by the dry climate better than almost any impact site on Earth. In the Petrified Forest, logs from the Triassic Chinle Formation were replaced mineral by mineral with silica more than 200 million years ago.

Every large lake in Arizona was built

Arizona has no significant natural lakes. Every large body of water on the map is a reservoir behind a dam. Lake Mead, held back by Hoover Dam since 1936, is the largest reservoir in the United States by capacity. Lake Powell formed behind Glen Canyon Dam in 1963 and drowned a canyon system that few people ever saw. Lake Havasu sits behind Parker Dam, and Theodore Roosevelt Lake, completed in 1911 on the Salt River, was the first of the works that made Phoenix agriculture possible.

The Central Arizona Project canal, finished in 1993, runs 336 miles from Lake Havasu and lifts Colorado River water almost 3,000 feet uphill to reach Phoenix and Tucson. The trade has been steep. The Santa Cruz River through Tucson and long stretches of the Gila, both of which once ran year round, are now dry sand for most of the year.

A border bought for a railroad, and a corner shared by four states

Arizona's southern boundary with Mexico is not where the 1848 treaty put it. The Gadsden Purchase, ratified in 1854, bought roughly 29,670 square miles specifically to give a southern transcontinental railroad a low, flat crossing, moving the line south of the Gila River and bringing Tucson into what became Arizona.

The northeastern corner touches Utah, Colorado and New Mexico at the only point in the country where four states meet, fixed by survey markers rather than by any natural feature. The western border was meant to follow the Colorado River, but the river shifted and twentieth century channel straightening left parcels of Arizona stranded on the California bank, so the two states eventually settled the line by compact rather than let it keep wandering. About a quarter of Arizona is tribal land, and the Navajo Nation, spilling across three states at roughly 27,000 square miles, is the largest Indian reservation in the United States.

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