The falls do hold one world record: they may be the fastest moving in the world geologically. The water is constantly eating away at the lower layer of rock, including material directly underneath the capstone. When enough of the supporting layer wears away, the upper layer collapses, dropping boulders at the base of the falls and moving the tip of the falls upstream. The waterfall has moved seven miles in the past 12,500 years.
2. Yellowstone National Park, Idaho, Montana and Wyoming
The nation’s first national park is basically the top of a still-sort-of-active volcano. Classic volcanoes are topped by a caldera, a caved-in area from which lava has erupted. Yellowstone also has a caldera, only it is hard to recognize because it is 45 miles across.
Yellowstone is the latest bit of North American crust to sit atop a stationary hotspot in the Earth’s mantle. A chain of volcanic rock from past eruptions marks where the continent has swept across the hotspot.
The last true eruption at Yellowstone was about 70,000 years ago, but the park still has plenty of seismic hydrothermal activity.
The hotspot fuels the crazy fumaroles (steam vents), hot springs, mud pots (hot springs with a lot of clay) and geysers. Old Faithful geyser gets most of the attention, but the park has 300 of them—the most anywhere on Earth.
1. Grand Canyon, Arizona
Ahh, the Grand Canyon. It's stunningly beautiful, a national treasure and perhaps the one place that will make you feel utterly insignificant in both space and time.
Our planet is about 4.6 billion years old. You can descend through almost half of that history by hiking to the bottom of the mile-deep canyon. The youngest layers at the top were deposited pretty much yesterday, geologically speaking, and the oldest, deepest layers of sedimentary rock about 2 billion years ago. Take a chart of the layers with you when you visit; even if you decide to view the canyon from above, it is the best place on Earth to try to comprehend the vastness of geologic time.
Editor's Note: An earlier version of this article mistakenly placed Mt. St. Helens in Oregon instead of Washington State. We regret the error.