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Schemes of work

Introduction to plate tectonics

Destructive plate margins

Collision margins

Constructive margins

Rift valleys

Faults

Hot spots

Conservative margins

Tectonic summary

Vulcanicity

Impact of volcanic activity

Volcanic hazards

Montserrat

Etna

An introduction to earthquakes

The effect of earthquakes

The impact of tectonic activity

 

 

 

Collision margins

Orogenesis is the name given to the process of fold mountain building. It involves at least two movements:

  • horizontal folding of sediments;
  • vertical uplift.

    In some cases a third movement is the extrusion of volcanic materials to build up cones with peaks higher than the general level of the mountains.
  • Here is an animation to illustrate this

    Growth of Everest


    The Indian Plate is moving into the Eurasian Plate at a rate of 5 cm a year. Prior to their contact there was an ocean in between the continents called the Tethys Ocean . This filled up with kms of sediment which when the plates eventually collided, was srapped off to form new continental rock. As both plates consist of continental crust, neither can sink. The land between them has been buckled and pushed upwards to form the Himalayas. This movement, which is still taking place, accounts for massive earthquakes which periodically occur where the plates meet. Evidence suggests that Mount Everest is increasing in height. Less obvious, however, is the effect of the collision felt by the whole of India. In January 2001 a major earthquake struck Gujarat , India killing over 20,000 and making up to 200,000 homeless Generally earthquake foci tend to be shallow, probably because there is no longer a subducting plate beneath the mountains.

    The more recent Sichuan earthquake of May 2008 (7.9 Mw) killing an estimated 68,000, was also attributed to the movement of the two plates