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Yellowstone Spotlight: Natural Bridge

When you compare how Yellowstone National Park visitor hubs got their names, Bridge Bay seems to have the most obscured origins.

Whereas some (Roosevelt, Grant) were named for figures important to Yellowstone features and others (Old Faithful, Canyon, Lake) were named for what you could see there, Bridge Bay has no obvious name. It’s too far from Fishing Bridge to warrant a connection.

Why the mystery? This is because, in part, the namesake of Bridge Bay has always been hidden—in plain sight, if you knew where to look. And that namesake is a unique feature: Natural Bridge, an impressively carved arch of rhyolite.

natural bridge august 2015

Thankfully, it’s a breeze getting to Natural Bridge, on foot or by bicycle. The trailheads start at Bridge Bay Campground, each about a mile long and taking you up a scant 100 feet in elevation. Natural Bridge towers 51 feet above Bridge Creek, overgrown with greenery and ensconced in tall stands of pine. You can get to the top of Natural Bridge via a switchback trail.

Natural Bridge has been known to Yellowstone visitors before the establishment of the Park. Indeed, the bridge was originally discovered and described on the 1871 Hayden Geological Expedition. It was termed “natural” because no human or animal force shaped it. Rather, Natural Bridge is the product of a few hydrological processes.

Firstly, parts of the rock were worn away through erosion from Bridge Creek. Secondly, frost helped gradually eke out Natural Bridge’s shape through a process known as “freeze-thaw plucking.” Since water expands when it freezes, water that seeped through cracks in the rock would widen, allowing for the same process to occur again and again, year after year, wedging rock apart. In Yellowstone, this process is especially marvelous, given that rhyolite is a supremely hard rock, the volcanic equivalent of granite.

Not that you can make a trek across it any time soon. Natural Bridge is closed to foot traffic out of safety concerns and fear that too much weight would undermine Natural Bridge’s structural integrity. And all the better, because Natural Bridge is better seen from a distance, the same way great bridges like the Brooklyn Bridge or Golden Gate Bridge seem better. From a distance, you can take in its shape, which has endured through the years.

About Sean Reichard

Sean Reichard is the editor of Yellowstone Insider and author of Yellowstone Insider For Families 2017.

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