Ocean-continent convergence
Topic: Continental Drift, Sea-floor Spreading and Plate Tectonics · NCERT: Class 11, Ch 4 "Distribution of Oceans and Continents"
Meaning
Ocean-continent convergence happens when an ocean plate and a continental plate move towards each other. Ocean crust is heavier, so it sinks under the lighter continental crust. This sinking is called subduction. A deep trench forms offshore. As the plate sinks it causes deep earthquakes, and part of it melts. The magma rises to form volcanoes on land. The edge of the continent is squeezed into fold mountains.
Example
Off South America, the Nazca plate sinks under the South American plate along the Peru-Chile Trench. This built the Andes, a range of fold mountains with volcanoes. It also causes Chile's frequent earthquakes. The Cascades in North America formed in the same way.
Don't confuse with
- Ocean-ocean convergence: both plates are oceanic, so the result is a curved chain of volcanic islands (an island arc) in the sea, not mountains on a continent.
- Continent-continent convergence: neither plate sinks easily, so there is no deep trench and few volcanoes, as in the Himalayas.
Related concepts
- Convergent boundary
- Subduction zone
- Ocean-ocean convergence
- Island arc
- Continent-continent convergence
- Fold mountain
- Wadati-Benioff zone