Compare
and contrast ridge push and slab
pull.

Ridge push is a process in which the unlifted ridge is thought to push the oceanic plate towards the subduction zone. Slab pull is a process where by the weight of a subducting plate help to pull the trailing lithosphere into subduction zone. Ridge lush is cause by the potential energy gradient from the high topography. Slab pull is caused by negative buoyancy of the subducting plate.

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

It is useful for historians to write narratives so that history can be passed on from their point of view.  think about a story being told in third person, then think about it again being told in first person, by someone who actually experienced the event.