Geography · Ch 10 — Distribution of Oceans and Continents
Movement of the Indian Plate
Movement of the Indian Plate
The diagram is a map-based reconstruction of the Indian plate’s northward journey over the last 71 million years. The Eurasian plate is shown as a shaded landmass across the top, with the Indian Ocean occupying the space below. The Indian landmass itself appears not as a single shape but as a series of dashed outlines, each representing the subcontinent at a different moment in deep time. Four such positions are marked, labelled by their age: 71 million years ago, 55 million years ago, 38 million years ago, and 10 million years ago. The oldest position, 71 million years ago, sits far to the south, near a box labelled “EARLY” INDIA, and the successive outlines step northward in sequence. The final outline, labelled “INDIA TODAY,” lies against the southern edge of the Eurasian plate, effectively in its present location.
Arrows connect these successive positions, pointing northward and showing the direction of convergence. A single large grey arrow sweeps across the map to emphasise the overall drift — the entire plate moving as one body from the southern ocean toward Asia. The Equator is drawn as a marked line across the map, and it is significant: the early positions of India lie south of it, while the later ones cross it and continue north. This placement is not incidental — it visually confirms that the subcontinent spent much of its journey in the Southern Hemisphere and only crossed the Equator relatively late in its history.
What the diagram teaches is the sheer scale and duration of plate motion. The Indian plate did not simply slide a short distance; it travelled thousands of kilometres over tens of millions of years, from a position off the Australian coast to a head-on collision with Asia. The dashed outlines are not artistic flourishes — they are snapshots of a moving plate, each one a fixed point in a continuous process. The convergence arrows show that the motion was not random but directed, sustained, and ultimately forceful enough to close an entire ocean (the Tethys) and raise the Himalayas. …
The engine that drives plate movement is the slow churning of the hot, softened mantle lying beneath the rigid plates. This idea, first floated in the 1930s, later shaped Harry Hess’s thinking on seafloor spreading. The Indian plate is a perfect case study of how a single plate can carry both continental and oceanic crust across thousands of kilometres, collide with another continent, and build the world’s highest mountain range.
Boundaries of the Indian Plate
The Indian plate includes Peninsular India and the Australian continental portions. Its boundaries are a mix of convergent, divergent, and transform margins:
- Northern boundary — a subduction zone along the Himalayas, formed by continent–continent convergence.
- Eastern boundary — extends through the Rakinyoma Mountains of Myanmar towards the island arc along the Java Trench.
- Eastern margin — a spreading site lying east of Australia, in the form of an oceanic ridge in the southwest Pacific.
- Western margin — follows the Kirthar Mountain of Pakistan, extends along the Makrana coast, and joins the spreading site from the Red Sea rift southeastward along the Chagos Archipelago.
- Southern boundary — the boundary between India and the Antarctic plate is marked by an oceanic ridge (a divergent boundary) running roughly west–east and merging into the spreading site a little south of New Zealand.
The Northward Journey
India began as a large island situated off the Australian coast in a vast ocean. The Tethys Sea separated it from the Asian continent until about 225 million years ago. India is supposed to have started its northward journey about 200 million years ago, at the time when Pangaea broke apart.
About 140 million years before the present, the subcontinent was located as far south as 50°S latitude. At that time, the two major plates were separated by the Tethys Sea, and the Tibetan block was closer to the Asiatic landmass.
Collision and the Himalayas
India collided with Asia about 40–50 million years ago, causing the rapid uplift of the Himalayas. From 40 million years ago onwards, the event of formation of the Himalayas took place. Scientists believe the process is still continuing, and the height of the Himalayas is rising even to this date.