Tectonic plate
Also called: Lithospheric plate · Topic: Continental Drift, Sea-floor Spreading and Plate Tectonics · NCERT: Class 9, Ch 2 "Shaping of the Earth's Surface"; Class 11, Ch 4 "Distribution of Oceans and Continents"
Meaning
A tectonic plate, also called a lithospheric plate, is a huge, irregular slab of solid rock. It is made of the lithosphere, which is the crust plus the top part of the mantle. The lithosphere is 5-100 km thick under oceans and about 200 km thick under continents. Each plate moves as one rigid unit over the asthenosphere, a soft, partly molten layer below. Most plates carry both land and ocean floor. A plate is called continental or oceanic depending on which part is larger. Plates usually move a few centimetres a year. Their edges are where most earthquakes, volcanoes and fold mountains form.
Example
The Indian plate carries Peninsular India. It moves north-northeast at about 5 cm a year and pushes into the Eurasian plate. This is why the Himalayas are still rising.
Don't confuse with
- Continent: Wegener thought the continents moved by themselves. Plate tectonics says the whole plate moves and carries the continent with it, like a passenger on a raft.