3rd Grade Mountain Ranges
Volcanic mountains form when molten rock from deep inside the Earth erupts through the crust and piles up on itself. The island chain of Hawaii is actually the tops of volcanoes. Well-known volcanoes on land include Mount St. Helens in Washington State and Mount Fuji in Japan. Sometimes volcanic eruptions break down mountains instead of building them up, like the 1980 eruption that blew the top off Mount St. Helens.
Plateau mountains are similar to dome mountains, but form as colliding tectonic plates push up the land without folding or faulting. They are then shaped by weathering and erosion.
Fold mountains are the most common type of mountain. The world's largest mountain ranges are fold mountains. These ranges were formed over millions of years. Fold mountains are formed when two plates collide head on, and their edges crumbled, much the same way as a piece of paper folds when pushed together. The upward folds are known as anticlines, and the downward folds are synclines.Examples of fold mountains include:
Himalayan Mountains in Asia
the Alps in Europe
the Andes in South America
the Rockies in North America
the Urals in Russia
When magma pushes the crust up but hardens before erupting onto the surface, it forms so-called dome mountains. Wind and rain pummel the domes, sculpting peaks and valleys. Examples include the Black Hills of South Dakota and the Adirondack Mountains of New York.
Other types of mountains form when stresses within and between the tectonic plates lead to cracking and faulting of the Earth's surface, which forces blocks of rock up and down. Examples of fault-block mountains include the Sierra Nevada in California and Nevada, the Tetons in Wyoming, and the Harz Mountains in Germany.
Fault Block Mountains