The Plate Tectonics

Plate tectonics refers to the theory widely accepted in the 1960s and 1970s that the earth’s crust and upper mantle are composed of tectonic plates that continually move or drift. This motion can cause earthquakes in various magnitudes and trigger volcanic activities.  During major earthquakes the seafloor also moves and can generate huge ocean waves or tsunamis.

Plate tectonics also builds on the 20th century concepts of continental drift, another theory stating that 175 million years ago all the continents moved together in one giant landmass.

In the scientific study of the earth’s origin and structure, the word plate refers to a large slab of rock.  On the other hand, tectonics is a Greek word which means “to build”.

The Earth has an interior part composed of the lithosphere (outer layer) and the asthenosphere (inner layer). The outer layer has seven major plates or crusts drifting or floating on top of the inner layer.  It is interesting to know that one side of the plate builds new crust while another side destroys old crust.

It is on the major plates that the continents and oceans rest. The tectonic plates move laterally either by pushing against another, moving away from each other or sliding past one another.  The shifts happen because of the movement of the soft mantle underneath while the heat from the core of the earth is the driving force for this motion.  The plates move  between  a centimeter to 15 centimeters  in a year.

One of the consequences of plate tectonics is the earthquake zone called the Pacific Ring of Fire. It is around this region that earthquakes, volcanic activities, build up of mountains and formation of oceanic trench occur.

There are 7 major plates and the biggest is the Pacific Plate at over 103 million square kilometres.

Major Plates

  • African Plate
  • Antarctic Plate
  • Indo-Australian Plate
  • Eurasian Plate
  • North American Plate
  • Pacific Plate
  • South American Plate

Minor Plates

  • Arabian Plate
  • Caribbean Plate
  • Cocos Plate
  • Juan de Fuca Plate
  • Nazca Plate
  • Philippine Sea Plate
  • Scotia Plate

Recommended Articles:

Japan Sits on the Ring of Fire

The Tokai Earthquake

Pacific Ring of Fire



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