Visitors to Chicago's Willis Tower—the Western Hemisphere's second-tallest building—got quite a scare Wednesday night when the floor of a glass observation box protruding from the 103rd story appeared to crack.
If you're like us, the incident might have left you wondering, "Could the same thing happen at the famed Grand Canyon Skywalk?" Well, yes, but that shouldn't stop you from going out onto the glass.
Here's why. No one was hurt in the Willis Tower incident because the cracks appeared in the floor's protective coating, not in the floor itself. In 2009, building operators changed the skyscraper's name (to our everlasting consternation) from the Sears Tower and introduced these four glass Skydeck boxes, known collectively as The Ledge. Six million visitors have stepped onto The Ledge since then, often surrounded by large crowds.
There was nothing unusual about Wednesday night. Tourist Alejandro Garibay and his four family members were standing on one of the ledges (which are designed to hold five tons), when they heard an ominous noise beneath their feet. The floor of the ledge appeared to be cracking.
They stepped off—as most smart people would. But despite media hype to the contrary, they were never in true danger.
"At no time whatsoever was the integrity of the structure compromised," says Willis Tower spokesman Bill Utter. "Willis Tower Observation Decks Crack" may make for a sexy headline, but that's not how the structure works. According to Utter, the surface's non-glass protective coating occasionally cracks, which is what happened Wednesday. "The protective layer did exactly what it was supposed to do," he said, emphasizing that visitors were never threatened.
At worst, the cracks showed that the deck's floor—made from three layers of half-inch thick glass—was under unusually high stress. But the threshold for cracks in the protective surface is far lower than that of the floor itself. Scary? Yes. Truly dangerous? Not really.
So if you have reservations to visit the Grand Canyon's Skywalk, that other glass-floored observation deck, don't cancel them. Projecting 70 feet from the canyon's rim and more than 3,500 feet above the Colorado River, the Skywalk is an engineering marvel designed to sustain the force of an 8.0 magnitude earthquake. In other words, it's really freaking strong.
And even though the walkway could support 822 people weighing 200 pounds each, operators only allow 120 visitors on it at a time. So you'll be fine if you step out onto the bridge's 2.8-inch thick, five-layer glass floor.
But if you've still got some butterflies in your stomach and decide to skip the thrill, we won't judge you. Just know that even if any cracks appear, you likely won't go plummeting to the bottom of the canyon.