DISTRIBUTION OF CONTINENTS AND OCEANS-3

PRERNA FOR IAS

         Mehnat Aapki, Guidance Humari

         Roz ki Prelims Practice — Experts ke Saath

DISTRIBUTION OF CONTINENTS AND OCEANS-3

1. Oceanic–Oceanic Divergence

Oceanic–Oceanic Divergence occurs when two oceanic plates move apart beneath the ocean. Magma rises through the opening created by plate separation and solidifies to form new basaltic oceanic crust. Continuous volcanic activity produces long underwater m`ountain chains known as mid-ocean ridges. These ridges are the primary sites of sea-floor spreading and are associated with shallow earthquakes. As new crust forms, older crust moves away from the ridge on both sides. The Mid-Atlantic Ridge is the world's best-known example. Oceanic divergence continuously enlarges ocean basins and renews the Earth's oceanic lithosphere.

2. Continental–Continental Divergence

Continental–Continental Divergence occurs when two continental plates begin moving apart due to extensional forces. Initially, large cracks or faults develop, forming rift valleys. As divergence continues, magma rises through the fractures, causing volcanic activity and thinning of the continental crust. Eventually, if separation continues for millions of years, a new ocean basin may develop between the two continents. The East African Rift System represents an active example where Africa is slowly splitting into two parts. Continental divergence marks the earliest stage of ocean formation and demonstrates the dynamic evolution of Earth's continents.

3. Convergent Plate Boundary

A Convergent Plate Boundary forms where two tectonic plates move toward each other due to compressional forces. Depending on the type of plates involved, one plate may sink beneath another through subduction, or both continental plates may collide to form mountain ranges. Convergent boundaries are characterized by powerful earthquakes, volcanic eruptions, deep-sea trenches, island arcs, and fold mountains. They are known as destructive boundaries because old crust is recycled into the mantle. The Andes Mountains, Himalayas, Japan Trench, and Mariana Trench are prominent examples of convergent plate boundaries.

4. Oceanic–Oceanic Convergence

Oceanic–Oceanic Convergence occurs when two oceanic tectonic plates collide. Since one plate is usually older, colder, and denser, it subducts beneath the other into the mantle. This process forms deep-sea trenches, volcanic island arcs, and frequent earthquakes. As the subducting plate melts, magma rises through the overriding plate to create volcanic islands. The Mariana Trench, the deepest part of the world's oceans, and the Japanese Island Arc are classic examples of oceanic-oceanic convergence. These boundaries are highly active zones where crust is continuously destroyed and recycled into the mantle through subduction.

5. Oceanic–Continental Convergence