Ninety East Ridge
Topic: Continental Drift, Sea-floor Spreading and Plate Tectonics · NCERT: Beyond NCERT
Meaning
The Ninety East Ridge is a long, straight mountain range under the sea in the eastern Indian Ocean. It runs along about 90°E and is some 5,000 km long. It is the track of the Kerguelen hotspot. A hotspot is a fixed spot where very hot rock rises from deep inside the earth and melts. As the Indian plate moved north over this hotspot, lava kept piling up on the sea floor. This left a line of volcanic rock behind the moving plate. The ridge matters because it records the path India took on its journey north.
Example
The ridge lies on the floor of the eastern Indian Ocean, south of the Bay of Bengal. It runs almost due north–south, close to the 90°E line of longitude. The same Kerguelen hotspot probably also made the Rajmahal Traps in eastern India.
Don't confuse with
- Mid-oceanic ridge: plates pull apart at a mid-oceanic ridge, and new crust is made there all the time. The Ninety East Ridge is only a hotspot track. No plates are spreading along it.
- Chagos-Laccadive Ridge: this ridge is the track of the Reunion hotspot, on the western side of India. The Ninety East Ridge is the track of the Kerguelen hotspot, in the east.