Tectonic plate interactions are of three different basic types:

• Divergent boundaries are areas where plates move away from each other, forming either mid-oceanic ridges or rift valleys.
• Convergent boundaries are areas where plates move toward each other and collide.
  • Subduction zones occur where an oceanic plate meets a continental plate and is pushed underneath it. Subduction zones are marked by oceanic trenches. The descending end of the oceanic plate melts and creates pressure in the mantle, causing volcanoes to form.
  • Obduction occurs when the continental plate is pushed under the oceanic plate, but this is unusal as the relative densities of the tectonic plates favours subduction of the oceanic plate.
  • Orogenic belts occur where two continental plates collide and push upwards to form large mountain ranges.
• Transform boundaries occur when two plates grind past each other with only limited convergent or divergent activity.

Table of contents

1 Divergent Boundaries 2 Subduction Zones 3 Orogenic Belts 4 Transform Boundaries

Divergent Boundaries

• The Great Rift Valley in eastern Africa
• The Mid-Atlantic Ridge system separates the North American Plate and South American Plate in the west from the Eurasian Plate and African Plate in the east
• The Gakkel Ridge is a slow spreading ridge located in the Arctic Ocean.

• The oceanic Nazca Plate is being subducted under the continental South American Plate at a rate of 10cm per year.
• The Pacific Plate is being subducted under the Eurasian and Philippine Plates.
• The Pacific Plate is also being subducted under the Indo-Australian Plate.

• The most dramatic orogenic belt on the planet is the one between the Indo-Australian Plate and the Eurasian Plate. The Himalayas are forming along this boundary.
• The Alps have formed due to the interaction of the African Plate and the Eurasian Plate.