The plate boundaries

Heat that arrives from the earth mantle drives the plate’s movement. This forming three general classes of plate boundaries. They are (i) divergent boundary (ii) convergent boundary (iii) transform boundary.

Divergent boundaries are reflected by oceanic ridge. At this boundary plates are move apart from other, and new sea-floor materials accumulated at oceanic spreading center. It added addition materials to earth surface. Therefore it called as constructive boundary.  Examples are mid oceanic ridges and activated fault zones. Mild earth quakes and volcanic eruptions are often occurs at this location.  

In convergent boundary plates are collide each other. One plate is subducted into the other plate. Often denser one is sup ducted into the mantle. This activity called as subduction. We can define this activity into three categories.

• Ocean-to-ocean subduction: this kind of plate movements forms a deep trench where one plate descends or subducted.

• Continent-to-continent: When continent plate collides they cause fold and uplift the land into mountain ranges.

• Ocean-to-continent boundary: When continent plate and oceanic plates are collides, its form a deep trench where oceanic plate descends and a line of subduction volcanoes occurs on the continental plate.

This zone or subduction zones contains hydrous minerals which emissions hot water. This water melted the mantle and cause volcanic eruptions. For example Andes range in South America, Japan islands.

At transform boundary two plates are slide and past each other. This sliding boundary cause steep fracture. It’s called as transform fault. Tectonic activities are parallel with the boundary that forming a new crust or depleting the old crust. Specific earthquakes are occur result of this sliding. Best example was San Andrea’s earthquakes in California. This earthquake occurred at between the plates of pacific and north America transform boundary.  


Reference :

(1) Michael Allaby, Dr. Robert R. Coenraads, Dr. Stephen Hutchinson, Karen McGhee, Dr. John O'Byrne, Dr. Ken Rubin (2008): The Encyclopedia of Earth, Sydney. 

(2) Tom L. McKnight (1990): Physical Geography - A Landscape Appreciation: Prentice  Hall: USA.

(3) http://en.wikipedia.org/wiki/Plate_tectonics