May 19, 2009

Does Utah have the biggest natural arch in the world? Yes. Sort of. Depends on your definition of "biggest".

Mapping geologists with the Utah Geological Survey recently published an article in the May 2009 edition of Survey Notes that attempts to answer that question. "In nearly three decades of working in Utah's geology, I have been asked many times, 'What is the largest/longest/biggest arch in the world?'" says Grant Willis, article author and UGS mapping geologist. "For years I told people it was Landscape Arch in Arches National Park."

Landscape Arch in Arches National Park has a span of 290 feet, the longest of any arch in the world, and is unquestionably the most mind-boggling due to
its gravity-defying ribbon of rock that in places narrows to only 7 feet in thickness.

Over the years, Willis was told there were bigger arches such as Kolob Arch in Zion National Park, Rainbow Bridge in Rainbow Bridge National Monument, Tushuk Tash in China and Aloba Arch in the Sahara Desert.

The Natural Arch and Bridge Society (NABS; www.naturalarches.org) defined 'biggest' in terms of the span of the arch, which is the total horizontal length of the arch opening. Then NABS used high-precision laser devices to measure spans, many of which were in logistically and geographically difficult places to access.

Tushuk Tash is easily the highest arch with a vertical drop of 1,200 feet. However, its span is only 180 feet. The span of Aloba Arch measured 250 feet.

The two biggest arches are, in fact, in Utah. Kolob Arch comes in second place with a span of 287 feet. But the biggest arch, by a mere three feet, is Landscape Arch at 290 feet. Utah has six of the top 10 biggest arches in the world!