Distribution of Oceans and Continents | Class 11 Geography Notes

PLATE TECTONICS

Plate tectonics is a unifying theory developed in 1967 by McKenzie, Parker, and Morgan that explains the movement of Earth's lithosphere. The lithosphere, comprising the crust and upper mantle, is divided into rigid plates that move horizontally over the asthenosphere. Plates can be continental, oceanic, or mixed. The Earth has seven major plates and several minor plates. Major plates include Antarctica, North American, South American, Pacific, India-Australia-New Zealand, African, and Eurasian plates. Minor plates include the Cocos, Nazca, Arabian, Philippine, and Caroline plates. Plates are bounded by three types of boundaries: divergent (where plates move apart and new crust forms, e.g., Mid-Atlantic Ridge), convergent (where plates collide and crust is destroyed or deformed, including subduction zones), and transform (where plates slide past each other horizontally). Plate movement is driven by convection currents in the mantle caused by heat from radioactive decay and residual heat. This theory explains continental drift, sea floor spreading, earthquakes, and volcanoes comprehensively.

📊 Diagram: See figure_5, figure_6, figure_7, figure_8, figure_9: Various figures illustrating plate boundaries and continental positions through geological past.

🧪 Activity: Identify major and minor plates on a world map and classify their boundaries.

🔗 Connection: Leads to the specific case study of the Indian Plate movement.