Fold Mountains

1
Fold Mountains
2
Formation

• Form along both destructive and collision plate
  boundaries, in other words where two plates are
  pushing towards each other.
• The best examples are the Himalayas, the Rockies,
  the Andes and the Alps, all of which are huge
  fold mountain ranges caused by the collision of
  two plates.

3
Theory

• The general theory is that as two plates, with
  land masses on them, move towards each other they
  push layers of accumulated sediment in the sea
  between them up into folds.
• Thus most fold mountains will continue to grow,
  as the plates constantly move towards each other.

4
Fold Mountains Constructive Boundaries
5
Formation

• As already seen, at a destructive plate boundary
  the oceanic plate is subducted beneath the
  continental one.
• The molten material then rises to the surface to
  form volcanoes, either in an island arc (e.g. the
  West Indies) or on the continental land mass
  (e.g. the volcanoes of the Andes).
• In both cases Fold Mountains can be formed.

6
Formation

• When the Nazca plate dives under the South
  American one, their motion forward also has been
  pushing sediment together.
• This, over millions of years, has been pushed up
  into huge fold mountains The Andes.
• Within them there are also volcanoes as the
  mountains are above the subduction zone.

7
Formation

• If an island arc has been formed, the same idea
  occurs.
• Over millions of years the movement of the two
  plates together will push the island arc nearer
  to the continent.
• As this occurs the sediments on the seabed are
  folded up to become huge mountains.

8
Fold Mountains Collision Margins
9
Formation

• These occur less frequently, but two excellent
  examples are the Himalayas, where the Indian
  plate is moving North and East towards the
  stationary European plate, and the Alps, formed
  by the collision between the African and Eurasian
  plates.
• In these examples both plates are Continental
  ones, and so can neither sink nor be destroyed.
• The material between them is therefore forced
  upwards to form the mountains.

10
Formation

• For the Himalayas the material that now forms the
  mountains was originally on the bottom of the
  non-existent Tethy's Sea.
• As the Indian plate pushed towards the Eurasian
  one, the sediments were folded up to form the
  Himalayas, leaving the only trace of the sea to
  be the fossilised shells that you can find high
  up in the mountains.