How Are Mountains Formed
Mountains are formed over long periods of time by forces of the earth. Mountains just don’t appear in any place. Most are formed when plates, or huge pieces of the Earth’s crust, pull and push against each other. Great mountain ranges are formed by the movement of tectonic plates. Convection currents deep in the mantle of the earth, begins to well up towards the surface. As the pressure increases, it sets the crustal plates in motion. There are different kinds of mountains – Volcanic, Folded, Fault-block, and Dome mountains.
Volcanic mountains are formed when magma comes up through cracks in the Earth’s crust and explodes out lava and ash. The Hawaiian volcanoes, Mt. Hood, Mt. Etna, Vesuvius, and Mt. Saint Helens are examples of volcanic mountains. Rocks are hard but in time they can bend or fold producing Folded mountains. The Alps formed as the Eurasian plate pushed against the African plate. Other examples of folded mountains are the Rockies, Himalayas, Appalayas, and the Andes. Fault-block mountains are formed when one plate pushes or pulls away from another plate.
In the Earth, hot currents of magma or molten rock may well up and crack the weakened crust above. As the crust cracks, blocks of rock rise or fall forming Fault-block mountains. Examples of these mountains are the Sierra Nevada in California and the Grand Tetons in Wyoming. Dome mountains are formed by the same kind of molten rock that forms Volcanic mountains. As magma comes up in a crack in the Earth’s crust, it does not come to the surface, but the molten rock pushes the ground up into a dome. Examples are Yosemite’s
Half Dome, the Adirondacks in New York, and the Black Hills in South Dakota. Some mountains started at the bottom of the sea. Scientists found that out when they took limestone off Mt. Everest and found dead sea creatures. Limestone is a kind of rock that is formed very slowly over thousands of years. Animals and plants that get stuck in limestone are called fossils. Limestone and fossils are common in most mountains that originated at the bottom of the sea. It is really amazing how mountains are formed by forces of the earth.