The Continental Drift Theory was comprehensively put forward by German meteorologist Alfred Wegener in 1912. He proposed that all continents once existed as a single supercontinent called Pangaea (meaning "all earth"), surrounded by a massive mega-ocean called Panthalassa (meaning "all water").
About 200 million years ago, Pangaea began to split into two large landmasses:
These two masses subsequently broke down into the smaller, distinct continents we recognize today.
Several lines of scientific evidence support the historical connection of the continents:
Wegener suggested two primary forces to explain the movement of continents, though both were later deemed inadequate by contemporary physicists:
In the 1930s, Arthur Holmes proposed the Convectional Current Theory. He argued that thermal differences generated by radioactive decay within the Earth's mantle create convective cells. This system of currents provided the physical mechanism for crustal movement that Wegener's theory lacked.
Post-WWII ocean mapping revealed that the ocean floor is not a flat plain but contains complex relief features. It is divided into three major provinces:
Seismic and volcanic activities are highly concentrated along specific zones. Earthquakes along the mid-oceanic ridges occur at shallow depths, whereas those along the Alpine-Himalayan belt and the rim of the Pacific Ocean are deep-seated. The rim of the Pacific Ocean is known as the Ring of Fire due to its high concentration of active volcanoes.
In 1961, Harry Hess proposed the concept of Sea Floor Spreading. He argued that constant volcanic eruptions along the crests of mid-oceanic ridges release lava that cools to form new oceanic crust, pushing the older crust symmetrically away on either side.
Key evidence supporting this hypothesis includes:
In 1967, McKenzie, Parker, and Morgan formulated the theory of Plate Tectonics. A tectonic plate is a massive, rigid slab of solid rock composing both continental and oceanic lithosphere. The lithosphere varies in thickness from $5\text{ to }100\text{ km}$ in oceanic areas to about $200\text{ km}$ in continental regions.
The Earth's surface is divided into seven major plates and several minor plates:
| Major Plates | Minor Plates |
|---|---|
| Antarctic Plate | Cocos Plate (Central America & Pacific) |
| North American Plate | Nazca Plate (South America & Pacific) |
| South American Plate | Arabian Plate (Saudi Arabian landmass) |
| Pacific Plate | Philippine Plate (Asiatic & Pacific) |
| India-Australia-New Zealand Plate | Caroline Plate (Philippine & Indian plate) |
| African Plate | Fuji Plate |
| Eurasian Plate | - |
Tectonic plates interact along three distinct types of boundaries:
Magnetic striping parallel to mid-oceanic ridges allows scientists to calculate plate velocities:
The primary driving force behind this movement is the slow, circular convective flow of hot, softened mantle material beneath the rigid lithospheric plates.
The Indian plate includes both Peninsular India and the Australian continental landmass. Its northern boundary is defined by the continent-continent convergence zone along the Himalayas.
The historical movement of the Indian plate is characterized by several key phases: