In reality it is difficult for humanity to have any influenceover the forces of nature. It may be possible to make a smalldifference to a lava flow by building a dam in from of an advancingflow, in the hole that this will divert the flow round somethingthat you want to protect. Or one could try cooling the flow frontwith water jets to see if this will cause a diversion.However expect the lav to overtop theses dams if the flowcontinues.