Mountains Fold mountains and Block mountains

By Odessa Ng

How Are Mountains formed?

!   Many of the greatest mountain ranges are formed because of enormous collisions between continents.

Left: A part of the Himalayas

Types of Mountains

!   Fold Mountains

!   Fault-block Mountains (Block Mountains)

!   Volcanic Mountains

Fold Mountains – The Rockies Block Mountains – Teton Range

Fold Mountains !   They are mountains formed from the folding of the Earth’s

crust

!   Usually found along the edge of continents

!   Form both along constructive and destructive boundaries

!   Most continue to grow as the plates constantly move

Structure

How are they formed?

!   Fold mountains are formed when two continental plates collide (or one continental plate colliding with an oceanic plate).

!   The colliding crust is compressed and pushed upwards (uplifted), forming mountains. (Fig 1)

Fig 1

The Himalayas

!   World’s largest mountain range

!   Highest peak: 8000 meters

!   The Indo-Australian plate had been continuously colliding into the Eurasian plate for the past 40 millions of years, continuously uplifting the Himalayas.

The Urals

!   Runs approximately from north to south through Western Russia

!   Eastern side: considered a natural boundary between Europe and Asia

!   250 – 300 million years old

!   Formed due to collision of East European platform and Siberian plate

!   Rich in precious stones, metal ores, coal

ON THE MAP

The Andes

The Urals

Alps

The Himalayas

Anticline and Syncline

Anticline Syncline

The Alps

Block Mountains

!   These mountains form when faults or cracks in the earth's crust force some materials or blocks of rock up and others down.

!   Instead of the earth folding over, the earth's crust fractures (pulls apart). It breaks up into blocks or chunks. Features: A steep front side, a

sloping back side

Sierra Nevada Mountains

!   In the US states of California and Nevada

!   640 km north to south

!   Features: Lake Tahoe, Mount Whitney, Yosemite Valley sculpted by glaciers made of 100 million year old granite

!   The present day mountains have only grown during the past 5 million years

!   Movement of plates in the Earth’s crust caused geological activities that formed these peaks.

ON THE MAP

Harz

Sierra Nevada, U.S.

Impacts

“Forestry is a key economic activity with the planting and harvesting of trees e.g. in the Alps. There are times, however, when forestry can be damaging e.g. in the Himalayas local people and logging companies have cut down large numbers of trees causing large-scale deforestation which leads to

problems of soil erosion and flooding.”

“Farming is the main primary activity but often only cattle and sheep rearing is possible due to the very cold, wet climate, the altitude and steepness of the slopes. Agricultural machinery is difficult to use and there is a very short growing season. In mountains such as the Andes and Himalayas, terraces (steps) have been cut into the hillsides to

allow crops such as vines and fruit to be grown.”

The End