Mountain FormationChapter 5.3

Mountains1.Mountains

a.A mountain is a natural elevation of the Earth’s surface rising abruptly to a summit.

b.A mountain range is a group of adjacent mountains with the same general shape and structure.i.For example: Mt. Everest is in the Himalaya

mountain range and Mt. St. Helens is in the Cascade mountain range.

Mountainsa.A mountain system is a group of adjacent

mountain ranges.i.The Smoky, Blue Ridge, Cumberland, and

Green mountain ranges make up the Appalachian mountain system.

b.A mountain belt is a group of large mountain systems. i.The two major mountain belts on Earth are

the circum-Pacific belt and the Eurasian-Melanesian belt.

Plate Tectonics and Mountains1.Plate Tectonics and Mountains

a.Scientists believe that these two major mountain belts are formed by convergent plate boundaries and that most mountain were formed by colliding lithospheric plates.

b.While some mountain belts do not lie along active plate boundaries, evidence suggest that these ranges formed where plates collided in the past.

Plate Tectonics and Mountains

a.Mountains can form at the three types of plate boundaries.i.Continental-Oceanic

1.In this collision the oceanic crust subducts under the continental crust forming high mountains.

2.It is also believed that some of these mountains are caused by terranes being scraped off.

3.Volcanic mountains can also be formed at this type of boundary.

Plate Tectonics and Mountainsi.Oceanic-Oceanic

1.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.

ii.Continental-Continental1.The Himalaya Mountains were formed by

two continents colliding. This can cause severe earthquakes in the area. These earthquakes still occur today.

Types of Mountains1.Types of Mountains

a.Mountains are classified according to the way the crust was deformed and shaped.

b.Folded Mountains & Plateausi.Folded mountains are landforms

created when tectonic movements bend and uplift rock layers. Basically, tectonic movements squeeze rock layers together.

Types of Mountainsi.Folding is evident in the rock layers of

mountains formed this way. ii.Plateaus are large areas of flat-topped

rocks high above sea level and are formed by the same force that forms folded mountains.

Types of Mountains

1.Plateaus are formed when thick, horizontal layers of rock are uplifted, generally next to a mountain ranges.

2.The Tibetan and Colorado plateaus are next to the Himalayan and Rocky mountains.

Types of Mountains a.Fault-Block Mountains & Grabens

i.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.

1.An example of fault-block mountain is the Sierra Nevada mountain range of California.

Types of Mountains

i.Grabens are long, narrow valleys formed by faulting and downward slippage of crustal blocks.

1.Grabens are formed by the same force that forms fault-block mountains.

2.An example of a graben is Death Valley in California.

Types of Mountains

a.Volcanic Mountainsi.Volcanic mountains are formed when

molten rock erupts onto the Earth’s surface and can develop on land or ocean floor.

ii.Most volcanic mountains are formed on divergent plate boundaries and along mid-ocean ridges.

Types of Mountains

i.Hot spots are pockets of magma beneath the Earth’s crust that erupt onto the surface.

1.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.

2.The main island of Hawaii is about 9km tall with only 4km above sea level.

Types of Mountains

a.Dome Mountainsi.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.

1.Examples include the Black Hills of South Dakota and the Adirondack mountains of New York State.