What features would rivers exhibit when they cross the fall line?

Once the rivers cross the fall lines it typically manifests with the occurrence of rapids and waterfalls. A fall line represents a geomorphologic break that changes the border lines between a higher situated region made out of relatively hard crystalline basement rock and a coastal plain made out of softer sedimentary rock.

The answer is cultural

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