The Appalachian Mountains aren't the world's largest mountains. And though they stretch from Canada to Alabama, they aren't even the world's longest (that honor goes to the mid-ocean ridge, a chain 40,389 miles long). However, the Appalachian chain does stand among the world's oldest mountains, with some of its rocks dating back 1.2 billion years — a milestone that makes these peaks older than the Atlantic Ocean.
The oldest parts of the Appalachian Mountains began to rise when our planet looked much different. At the time of their creation, North America was still attached to Europe and most of Asia, making up the supercontinent Laurasia. However, a collision between Laurasia and Gondwana — the massive continental fusion that included Africa, India, South America, Australia, and Antarctica — would eventually create Pangaea, and the first Appalachian peaks along with it. As Pangaea formed around 320 million years ago, the earliest Appalachian mountains began to grow, reaching far higher into the sky than they do today; initially, the southern subrange we call the Blue Ridge Mountains had the largest summits in the world. However, Pangaea eventually broke apart, leaving a rift that would become the Atlantic Ocean about 150 million years ago, as the continents separated.
Today, around 3 million people hike through the Appalachian Mountains along the Appalachian Trail, a feat that wouldn't at all be possible had the mountain range remained as high as the Himalayas. Thankfully for backpackers, millions of years of erosion have brought the still-stunning mountain chain to a more trekkable level, averaging a more manageable 3,000 feet above sea level.
The Hoover Dam can be called both a monument and a marvel, reaching a staggering 60 stories toward the sky and at one time reigning as the world's largest dam. Read on for six facts about the Hoover Dam, from its original name to its dramatic World War II history.