The Appalachian Mountains are a system of mountains in eastern North America, stretching nearly 3,200 kilometers from the island of Newfoundland in Canada to central Alabama in the United States. They are among the oldest mountains on Earth, formed roughly 480 million years ago during the Ordovician Period. At their peak, they were once as tall as the modern Himalayas, but hundreds of millions of years of erosion have worn them down into a series of rolling ridges and valleys. The range is divided into several sections, including the Blue Ridge, the Great Smoky Mountains, and the White Mountains. The Appalachians are famous for the Appalachian Trail, one of the longest hiking-only footpaths in the world. The region is also historically significant for its massive coal deposits, which fueled the American Industrial Revolution, and for its unique folk culture and biodiversity, featuring some of the world's most diverse temperate deciduous forests.