Continental Drift Theory , proposed by Alfred Wegener in 1912 (published 1915), was the first comprehensive model explaining the movement and present configuration of continents. It posited that all landmasses were once joined as the supercontinent 'Pangaea' , surrounded by the ocean 'Panthalassa' .

Wegener’s Continental Drift Theory (1912) proposed that the supercontinent Pangaea broke apart about 200 million years ago into Laurasia (north) and Gondwanaland (south) , separated by the Tethys Sea. These masses drifted equatorward and westward, setting the stage for the formation of today’s continents, mountains, and oceans.

Alfred Wegener’s Continental Drift Theory (1912) proposed that continents were once united as Pangaea and later drifted apart. Multiple compelling geological, paleontological, and climatic evidences supported this idea, which, despite its criticism regarding the mechanism, laid the essential foundation for the modern Plate Tectonics Theory.

Arthur Holmes suggested mantle convection currents as the mechanism behind continental drift. Harry Hess and Robert Dietz later proposed Sea Floor Spreading , showing new crust forms at mid-ocean ridges and old crust subducts at trenches. Together these theories provided the scientific mechanism and empirical evidence that superseded the Continental Drift Theory and laid the foundation for the Plate Tectonic Theory.

Seafloor spreading was confirmed through geological, geophysical, and paleomagnetic evidence , providing the foundation for Plate Tectonic Theory. The theory explains Earth's lithosphere as divided into plates that move over the asthenosphere, shaping continents, oceans, and mountains.

Earth’s lithosphere is broken into rigid plates that float over the semi-molten asthenosphere . These plates move due to mantle convection currents , slab-pull, and ridge-push, leading to continental drift, earthquakes, volcanism, and mountain building.

Plate margins are the edges of tectonic plates, while plate boundaries are dynamic zones where two plates interact. Depending on movement, boundaries can be convergent (destructive) , divergent (constructive) , or transform (conservative) .

Tectonic plate interactions occur as convergent (destructive) , divergent (constructive) , or transform (conservative) boundaries. These interactions shape Earth's surface, forming mountains, trenches, volcanoes, and rift valleys.

Plate Tectonic Theory is the most widely accepted theory that successfully integrates earlier hypotheses like Continental Drift and Seafloor Spreading. It provides a comprehensive explanation for landform evolution , earthquakes , and volcanism by establishing the movement of the entire lithospheric shell.

An earthquake is the sudden shaking or trembling of the earth’s surface caused by the release of energy from the interior of the Earth. This energy travels in all directions as seismic waves , with the greatest impact at the epicenter .

Earthquakes are measured using instruments such as seismographs and seismometers, and evaluated in terms of magnitude (energy released) and intensity (damage caused). The Moment Magnitude Scale (Mw) is now the global standard for assessment, complemented by the Modified Mercalli Intensity (MMI) Scale.

Earthquakes are triggered by both natural geological processes (Plate Tectonics, Elastic Rebound Theory) and human activities (Reservoir-Induced Seismicity, Mining). Tectonic quakes are the strongest, while human-induced quakes are localized.

Around 90% of earthquakes occur along plate boundaries , concentrated in a few major belts such as the Circum-Pacific (Ring of Fire) , Mid-Atlantic , and Mid-Continental belts. Intra-plate earthquakes also occur but are less frequent.

India is divided into four seismic zones (Zone II to Zone V) based on the intensity of earthquakes experienced and the presence of active faults. The Seismic Zonation Map is prepared by the Bureau of Indian Standards (BIS) to guide disaster mitigation and construction standards.

Earthquakes cause widespread destruction through landslides, ground deformation, and secondary hazards like tsunamis. Their impact varies from local structural damage to global-scale disasters.

Volcanoes are vents or fissures on Earth's surface through which magma, gases, and ashes erupt. They are directly linked to Earth's internal heat and tectonic processes.

Volcanoes are unevenly distributed across the globe, mostly concentrated along tectonic plate boundaries . About 80% of volcanoes are located at convergent plate boundaries, 15% at divergent boundaries, and the rest occur as intra-plate hotspots .

Volcanic eruptions release gases, fragmented materials ( pyroclasts ), and molten lava. The violence of the eruption depends on the opening (fissure or central vent) and the viscosity of the magma (determined by its silica content).

Central eruptions occur through a vent or mouth and vary from calm, non-explosive outflows to violent explosive eruptions. They are classified into Hawaiian, Strombolian, Vulcanian, Pelean, and Plinian types, depending on lava viscosity , gas content, and eruptive style.

Volcanic activity produces diverse landforms depending on whether magma solidifies on the surface ( extrusive ) or below the surface ( intrusive ). Extrusive landforms include cones, craters, and plateaus, while intrusive landforms include batholiths , laccoliths , sills , and dykes .

Intrusive landforms form when magma solidifies beneath the Earth's surface. They cool slowly, producing coarse-grained igneous rocks (e.g., granite). These features strongly influence mountain building, mineralization, and landscape evolution.

Volcanic eruptions are powerful natural events that reshape landscapes, influence climate, and affect human life. Their impacts can be both constructive (soil fertility, energy, tourism) and destructive (loss of life, lahars, climatic disruptions).