🌋 Plate tectonics 3D
Plates move a few centimetres a year — about as fast as fingernails grow. Here millions of years pass in seconds.
Convergent: subduction
- Motion
- Plates move together; dense ocean plate sinks
- Features
- Deep trench, volcanic arc, earthquakes down to ≈ 700 km
- Example
- Andes (Nazca plate under South America), Japan, Cascades
The colder, denser oceanic plate dives into the mantle. Water released from it lowers the melting point of the mantle above, making magma that feeds a line of explosive volcanoes. The world's biggest earthquakes happen here (Chile 1960, M9.5).
- Earth’s rigid outer shell (lithosphere) is broken into ≈ 15 major plates riding on the slowly flowing mantle.
- New crust is made at ridges and destroyed at subduction zones, so Earth stays the same size.
- Ocean floor is young — nowhere much older than ≈ 180 million years — while some continental rock is over 4 billion years old.
- Plates are pushed at ridges and pulled most strongly by sinking slabs (slab pull).