A concentration of arches of marvelous variety has formed within the maze of sandstone fins at Arches National Park, one of the most popular in the United States. Balanced rocks and tall spires add to the splendor. Paved roads and short hiking trails provide easy access to some of the more than 1,500 arches in the park.

If you’re short on time, a drive to the Windows Section (23.5 miles round-trip) allows a look at some of the largest and most spectacular arches. To visit all the stops and hike a few short trails would take all day. The entrance fee of $10 per vehicle ($5 bicyclists) is good for seven days at Arches only. The park brochure available at the entrance station and visitors center has a map of major scenic features, drives, trails, and back roads.

An unusual combination of geologic forces created the arches. About 300 million years ago, evaporation of inland seas left behind a salt layer more than 3,000 feet thick in the Paradox Basin of this region. Sediments, including those that later became the arches, covered the salt. Unequal pressures caused the salt to gradually flow upward in places, bending the overlying sediments as well.

These upfolds, or anticlines, later collapsed when ground water dissolved the underlying salt. The faults and joints caused by the uplift and collapse opened the way for erosion to carve hundreds of freestanding fins. Alternate freezing and thawing action and exfoliation (flaking caused by expansion when water or frost penetrates the rock) continued to peel away more rock until holes formed in some of the fins. Rockfalls within the holes helped to enlarge the arches. Nearly all arches in the park eroded out of Entrada sandstone.

Eventually all the present arches will collapse, but we should have plenty of new ones by the time that happens. The fins’ uniform strength and hard upper surfaces have proved ideal for arch formation.

Not every hole in the rock is an arch. The opening must be at least three feet in one direction and light must be able to pass through. Although the term “windows” often refers to openings in large walls of rock, windows and arches are really the same.

Water seeping through the sandstone from above has created a second type of arch—the pothole arch. You may also come across a few natural bridges cut from the rock by perennial water runoff.

The Best of Arches National Park

• Balanced Rock
• Windows Section
• Delicate Arch Trail
• Fiery Furnace Trail
• Devils Garden Loop
• Tower Arch Trail