Mountain Formation

1. Mountain Formation Chapter 5.3

2. Mountains • Mountains • A mountain is a natural elevation of the Earth’s surface rising abruptly to a summit. • A mountain range is a group of adjacent mountains with the same general shape and structure. • For example: Mt. Everest is in the Himalaya mountain range and Mt. St. Helens is in the Cascade mountain range.

3. Mountains • A mountain system is a group of adjacent mountain ranges. • The Smoky, Blue Ridge, Cumberland, and Green mountain ranges make up the Appalachian mountain system. • A mountain belt is a group of large mountain systems. • The two major mountain belts on Earth are the circum-Pacific belt and the Eurasian-Melanesian belt.

4. Plate Tectonics and Mountains • Plate Tectonics and Mountains • Scientists believe that these two major mountain belts are formed by convergent plate boundaries and that most mountain were formed by colliding lithospheric plates. • While some mountain belts do not lie along active plate boundaries, evidence suggest that these ranges formed where plates collided in the past.

5. Plate Tectonics and Mountains • Mountains can form at the three types of plate boundaries. • Continental-Oceanic • In this collision the oceanic crust subducts under the continental crust forming high mountains. • It is also believed that some of these mountains are caused by terranes being scraped off. • Volcanic mountains can also be formed at this type of boundary.

6. Plate Tectonics and Mountains • Oceanic-Oceanic • In this collision the more dense oceanic plate subducts under the less dense oceanic plate and forms an arc of volcanic mountains on the ocean floor. • Continental-Continental • The Himalaya Mountains were formed by two continents colliding. This can cause severe earthquakes in the area. These earthquakes still occur today.

7. Types of Mountains • Types of Mountains • Mountains are classified according to the way the crust was deformed and shaped. • Folded Mountains & Plateaus • Folded mountains are landforms created when tectonic movements bend and uplift rock layers. Basically, tectonic movements squeeze rock layers together.

8. Types of Mountains • Folding is evident in the rock layers of mountains formed this way. • Plateaus are large areas of flat-topped rocks high above sea level and are formed by the same force that forms folded mountains.

9. Types of Mountains • Plateaus are formed when thick, horizontal layers of rock are uplifted, generally next to a mountain ranges. • The Tibetan and Colorado plateaus are next to the Himalayan and Rocky mountains.

10. Types of Mountains • Fault-Block Mountains & Grabens • Fault-Block mountains form where faulting breaks the earth’s crust into large blocks that become tilted, causing some blocks to drop down relative to other blocks. • An example of fault-block mountain is the Sierra Nevada mountain range of California.

11. Types of Mountains • Grabens are long, narrow valleys formed by faulting and downward slippage of crustal blocks. • Grabens are formed by the same force that forms fault-block mountains. • An example of a graben is Death Valley in California.

12. Types of Mountains • Volcanic Mountains • Volcanic mountains are formed when molten rock erupts onto the Earth’s surface and can develop on land or ocean floor. • Most volcanic mountains are formed on divergent plate boundaries and along mid-ocean ridges.

13. Types of Mountains • Hot spots are pockets of magma beneath the Earth’s crust that erupt onto the surface. • The Hawaiian islands were formed (are forming) over hot spots, and are the tips of volcanic mountains that have breached the surface of the ocean. • The main island of Hawaii is about 9km tall with only 4km above sea level.

14. Types of Mountains • Dome Mountains • A dome mountain is a landform created when molten rock pushes up rock layers on the Earth’s surface and the layers then are worn away in places, leaving separate high peaks. • Examples include the Black Hills of South Dakota and the Adirondack mountains of New York State.