What is the process by which he ocean floor sinks beneath a deep-ocean trench and back into the mantle known as?

I think the answer is subduction

Answer to your question is subduction

Csaudi arabia and wish u us: )

So  if  the sum of the enthalpies of the reactants is greater than the products, the  reaction  will be  exothermic.  if  the products side has a larger enthalpy, the  reaction  is  endothermic. you may wonder why  endothermic reactions, which soak up energy or enthalpy from the environment, even happen