Wadati-Benioff zone
Also called: Benioff zone · Topic: Continental Drift, Sea-floor Spreading and Plate Tectonics · NCERT: Beyond NCERT
Meaning
The Wadati-Benioff zone, also called the Benioff zone, is a sloping band of earthquakes under a subduction zone. It starts near an ocean trench and dips down into the mantle, as deep as about 700 km. The earthquakes happen inside the cold, sinking plate as it goes down. So the zone traces the path of the sinking plate. It explains why earthquakes near trenches are deep, while those at mid-ocean ridges are shallow. This topic is beyond NCERT.
Example
Under Japan, earthquakes get deeper the farther you go inland from the trench in the Pacific Ocean. They mark the Pacific plate sinking beneath Japan.
Don't confuse with
- Ridge earthquakes: earthquakes along mid-ocean ridges such as the Mid-Atlantic Ridge are shallow. They do not form a dipping band.
- Transform fault: it also has earthquakes, but they are shallow and lie along a vertical crack where plates slide sideways, not along a sloping, sinking slab.
Related concepts
- Convergent boundary
- Subduction zone
- Ocean-continent convergence
- Ocean-ocean convergence
- Island arc
- Continent-continent convergence
- Fold mountain