Importance Cartoon representation of the Subduction Factory, from Y. Tatsumi JAMSTEC.
Subduction zones are important for several reasons:
1. Subduction Zone Physics: Sinking of mantle lithosphere provides most of the force needed to drive plate motion and is the dominant mode of mantle convection.
2. Subduction Zone Chemistry: The cold material sinking in subduction zones releases water into the overlying mantle, causing mantle melting and fractionating elements (buffering) between surface and deep mantle reservoirs, producing island arcs and continental crust.
3. Subduction Zone Biology: Because subduction zones are the coldest parts of the Earth's interior and life cannot exist at temperatures >150°C, subduction zones are almost certainly associated with the deepest (highest pressure) biosphere.
4. Earth's Mixmaster: Subduction zones mix subducted sediments, oceanic crust, and mantle lithosphere and mix this with mantle from the overriding plate to produce fluids, calc-alkaline series melts, ore deposits, and continental crust. For this reason, scientists increasingly refer to the "Subduction Factory", and we are intermittently and rudely reminded of its operation by earthquakes and tsunamis.
Learning more about the physics, chemistry, and biology of subduction zones requires efforts that are increasingly interdisciplinary and international. Because of the central role that subduction plays in the solid Earth system, as well as its role in maintaining equilibrium between the mantle and the hydrosphere, understanding and teaching how subduction zones operate is a scientific challenge of the first importance.
Subduction zones are also being considered as possible disposal sites for nuclear waste, where the action would carry the material into the planetary mantle, safely away from any possible influence on humanity or the surface environment.
http://en.wikipedia.org/wiki/Subduction
