Around the world, hundreds of mountains and mountain ranges tower over the land. The mountains fascinate the adventurous, and every year, thousands of climbers take on the challenge of scaling mountains. What are these mountains that draw so many to their slopes? How did they come to be?
Mountains are natural landforms that rise 1,000 feet or more above their surroundings. You can find mountains all over the world and in all different types of environments, including on the ocean floor. You might think of a mountain as a big hill with steep, sloped sides. Rock and earth make up all mountains. Depending on the location, grass, snow, or ice could also cover them.
Geologists classify mountains into five basic kinds: fold mountains, fault-block mountains, dome mountains, volcanic mountains, and plateau mountains. These mountain types are formed in different ways.
Pieces of Earth's outer shell, called tectonic plates, constantly move because of gravity and the heat from Earth's core. Usually, the movements are gentle and gradual, so we don't feel them. But sometimes, the plates crash and slide against each other, creating an earthquake. These tectonic movements also cause mountains to form.
Fold mountains, the most common type, form when two tectonic plates collide, forcing sedimentary rock upward. This rock folds into layers on the Earth's crust and makes a mountain. The Alps in Europe are fold mountains.
Fault-block mountains occur along faults, which are cracks in Earth's crust. When pressure builds along these lines, some rock moves up and other rock moves down as the bedrock splits. This creates a series of "horsts," where the rock rises, and "grabens," where the rock drops. The Sierra Nevada in the western United States is a fault-block mountain range.
Dome mountains are also called upwarped mountains because the hardening of magma, or molten rock, deep underground pushes the rock layers above it and warps them upward. This makes a dome shape. The Adirondack Mountains in New York are dome mountains.
Volcanic mountains form like dome mountains, only for volcanic mountains, the magma breaks the surface and erupts. When the magma, called lava when it's above the surface, cools and hardens, it forms a layer of rock. This process repeats over and over until you have a mountain. Mount Vesuvius in Italy is a volcanic mountain.
Plateau mountains result from the erosion of a plateau. A variety of natural forces cause erosion, including weather and water. Of the five types of mountains, plateau mountains take the longest to form.
A mountain range is a series of neighboring mountains. They may or may not be geologically related, meaning that the same process may or may not have formed the individual mountains in the range. According to some geologists, some mountain ranges have stood for billions of years!
What is the tallest mountain in the world? You might think it's Mount Everest, which reaches an elevation, or height, of more than 29,000 feet. That's almost 5.5 miles! Measuring from sea level, Mount Everest is the tallest mountain on Earth. But if you measure the whole height, from bottom to top, the tallest mountain is Mauna Kea in the Pacific Ocean. Though only 14,000 feet above sea level, 60% of Mauna Kea, about 20,000 feet, extends into the sea. That means that Mauna Kea is almost 6.5 miles tall from top to bottom!
What if you wanted to look beyond Earth to the tallest mountain in the solar system? That award goes to Olympus Mons on Mars, which is more than twice as tall as Mount Everest. The spacecraft Mariner 9 discovered Olympus Mons in 1971.
On Earth, the Andes Mountains of South America claim the title of the longest above-water mountain range. The Andes stretch 4,300 miles along the west coast of the continent. Like with the tallest mountain, though, the question of which is the longest mountain range doesn't end there. If you consider ranges below sea level, the Mid-Ocean Ridge, winding its way below Earth's oceans, is the longest mountain range on Earth. This mountain range is an unbelievable 40,000 miles long! (Earth itself is about 25,000 miles around.) It traces the tectonic plate boundaries and can only be seen above the water in Iceland.
But which is the hardest mountain to climb? Many mountaineers would say it's K2, a mountain on the China-Pakistan border. Though it's not as tall as Mount Everest, more climbers have failed in climbing K2 than Mount Everest because of how steep it is, he danger of avalanches, and the unpredictable weather.