Plate tectonics is the theory that Earth’s outer shell i.e. the crust is divided into several plates that glide over the mantle, the rocky inner layer above the core. The plates act like a hard and rigid shell compared to Earth’s mantle. The plate movements are caused due to various factors like movements in the mantle, expansion and contraction of some parts of the Earth. When two tectonic plates move towards each other or away from each other or slide past each other, it results in earthquakes, volcanic activity, mountain building and oceanic trench formation.

Volcanic activity and earthquakes are widespread over the earth, but tends to be concentrated in specific locations. They are most likely to occur along the margins of tectonic plates.

• Volcanoes at convergent plate boundaries:

Ocean-Ocean plate collision and Ocean – Continent plate collision: In subduction zones where oceanic plates dive under continental plates. As the oceanic plate subducts beneath the surface, intense heat and pressure melts the rock. Molten rock material, magma, can then ooze its way toward the surface where it accumulates at the surface to create a volcano.

Circum-Pacific Region: Also known as “Pacific Ring of fire”: about two-thirds of the world’s volcanoes are found in this region. The chain of volcanoes extends from Aleutian islands into Kamchatka, Japan, the Philippines and Indonesia, southward into Pacific Islands of Solomon, Tonga and New Zealand. On the other side of the pacific, the chain continues from the Andes to Central America (Guatemala, Costa Rica and Nicaragua), Mexico and right up to Alaska. Example: Mt. Fuji, Mt.Vesuvius, Stromboli, Etna etc.

• Volcanoes at Divergent plate boundaries:

Divergent boundaries within continents initially produce rifts which eventually become rift valleys.  Example: In Africa’s East African Great Rift Valley– Mt.Kilimanjaro, Mt. Kenya, Mt. Cameroon.

Most active divergent plate boundaries occur between oceanic plates and exist as mid-oceanic ridges. Example: Mid- Atlantic ridge where there is a constant sea-floor spreading and formation of new plate boundaries. Iceland is a remarkable location in that a section of the north-Atlantic mid-ocean ridge is exposed on land.

Divergent boundaries also form volcanic islands which occur when the plates move apart to produce gaps which molten lava rises to fill.     

• Transform boundaries: where plates slide passed each other. The relative motion of the plates is horizontal. They can occur underwater or on land, and crust is neither destroyed nor created. Because of friction, the plates cannot simply glide past each other. Rather, stress builds up in both plates and when it exceeds the threshold of the rocks, the energy is released – causing earthquakes. California’s San Andreas Fault, where the North America and Pacific plates grind past each other with a mostly horizontal motion.

Conclusion:

Volcanoes and Earthquakes though a natural phenomenon have a huge impact on man and material as urbanization and globalization increases. The effects have impacts on flora, fauna and the global warming which can accelerate the climate change.