"I don't know..."
"Look, it took millions of years to form, it's been here millions of years, it'll be here for millions. And more are forming all the time. Be adventurous."
According to long-age views, various cliffs, arches, and other landforms were formed over huge amounts of time and are pretty much permanent. Except that they're not here to stay after all, since many famous landmarks around the world have been collapsing. Sure, you expect to see an ice arch collapse, but rock? Yes, it does. Some famous landmarks have interesting "before" and "after" photos. Sadly, a few have even resulted in fatalities, and sometimes people are not allowed to stand under arches and such, let alone, walk on the ones that were previous accessible.
|Delicate Arch, Moab, Utah, image credit NOAA / NGDC, John Lockridge, Longmont, CO|
Spectacular cliffs dominate long stretches of Australia’s coastline. As a youngster, my all-time favorite trip on Victoria’s Great Ocean Road was the famous London Bridge, a double-arched natural ‘bridge’ jutting spectacularly into the sea, named for its resemblance to its famous namesake. It was fun to walk out to the end (along with hundreds of other tourists at peak holiday times), knowing that you were traversing the foaming surf below via two strong arches of natural rock.To read the article in its entirety, click on "A dangerous view".
But no-one can do that any more. It all came to a dramatic end at about 3:30 pm on 15 January 1990, when the arch closer to the mainland collapsed unexpectedly, leaving two tourists stranded on the outer part—which was now of course an island.
They were rescued by helicopter just as night fell, and thankfully no-one was hurt.