Science 7: Unit E: Planet Earth Topic 7: Mountains

How Are Mountains Formed? Mountains building takes millions of years. Mountains building takes millions of years. Most mountain ranges are formed from the movement of tectonic plates, usually in a subduction zone from the compression of the Earth’s crust. Most mountain ranges are formed from the movement of tectonic plates, usually in a subduction zone from the compression of the Earth’s crust. A large mountain range is called a cordillera. The Canadian Rockies are part of the Western Cordillera which also includes the American Rockies and the Alaskan Rockies. A large mountain range is called a cordillera. The Canadian Rockies are part of the Western Cordillera which also includes the American Rockies and the Alaskan Rockies.

Faulting and Folding Sedimentary rock can be faulted or folded into mountains: Sedimentary rock can be faulted or folded into mountains: Faulting – The breaking of sedimentary rock as parts are pushed up over other rock. Faulting – The breaking of sedimentary rock as parts are pushed up over other rock. Folding – The bending, but not breaking of sedimentary rock as the crust is compressed and forced upwards. Folding – The bending, but not breaking of sedimentary rock as the crust is compressed and forced upwards.

Syncline and Anticline Synclines and anticlines are formed through the folding process. Synclines and anticlines are formed through the folding process. Syncline – the downward or bottom part of the fold. Syncline – the downward or bottom part of the fold. Anticline – The upward or top part of the fold. Anticline – The upward or top part of the fold.

Thrust Faulting and Fault Block Mountains Thrust Faulting – Sedimentary rock is broken into separate sheets or ‘slabs’ These sheets can then be pushed over or under other sheets. Thrust Faulting – Sedimentary rock is broken into separate sheets or ‘slabs’ These sheets can then be pushed over or under other sheets. Fault Block Mountains – Compression forces form the slabs and the continued pushing can cause the older rock to slide on top of the newer rock. Fault Block Mountains – Compression forces form the slabs and the continued pushing can cause the older rock to slide on top of the newer rock. Basement Rock – The bottom layer of the mountain which the other layers slide on top of. Basement Rock – The bottom layer of the mountain which the other layers slide on top of.

Complex Mountains When an oceanic plate meets a continental plate, it subducts under the continental plate. When an oceanic plate meets a continental plate, it subducts under the continental plate. This compression gives off heat and pressure which help to form mountains. This compression gives off heat and pressure which help to form mountains. Complex Mountains – mountains formed from melting and compression when an oceanic plate meets a continental plate. Complex Mountains – mountains formed from melting and compression when an oceanic plate meets a continental plate. The Rocky Mountains formed 500 million years ago when the Pacific plate subducted under the North America Plate and the N. America Plate edge began to thrust fault. The Rocky Mountains formed 500 million years ago when the Pacific plate subducted under the North America Plate and the N. America Plate edge began to thrust fault.

Young and Old Mountain Ranges Young Mountain Ranges – are jagged and rough. They have not been polished smooth by weathering. The Himalayas and Rockies are ‘young’ mountain ranges. Young Mountain ranges are growing higher every year due to compression. Young Mountain Ranges – are jagged and rough. They have not been polished smooth by weathering. The Himalayas and Rockies are ‘young’ mountain ranges. Young Mountain ranges are growing higher every year due to compression. Old Mountain Ranges – smooth and rounded peaks. They are polished smooth and are growing smaller every year due to the processes of weathering and erosion. Old Mountain Ranges – smooth and rounded peaks. They are polished smooth and are growing smaller every year due to the processes of weathering and erosion.

New Mountain Range Old Mountain Ranges