Chapter 11.3a Mountain Formation

Mountain Building at Convergent Boundaries Most mountain building happens at convergent plate boundaries. The colliding plates provide a compressional force that fold, fault, and metamorphose the thick layers of sediments deposited at the edges of landmasses. Magma is also important because it cam deform the rock further.

Ocean-Ocean Convergence Remember this takes place where 2 oceanic plate converge and 1 moves under the other. This leads to a volcanic island arc on the ocean floor. An example is the Aleutian Islands in Alaska. Ocean-ocean convergence produces volcanic mountains.

Ocean-Continental Convergence When an oceanic plate and continental plate collide we have mountain building. A good example is on the west coast of South America – the Andes mountains. Usually ocean-continental convergence makes mountain ranges with 2 parallel belts. The belt more inland will be made of volcanoes. The more seaward belt is called an accretionary wedge – have folded, faulted sedimentary and metamorphic rock. So the types of mountains formed by ocean- continental convergence are volcanic mountains and folded mountains.

Continent-Continent Convergence Where 2 continental plates collide, folded mountains are formed. An examples would be the Himalaya Mountains and the Tibetan Plateau.