Since dating of rocks by radiometric dating varies considerably and recent eruptions i.e. circa200 years give old ages how can this be reconciled?

Can you be more specific - what actual example can you cite where the reported data is inconsistent with known facts? In general radiometric dating of lava flows will give you information regarding the age of the formation of the lava, not the age of the eruption that brought that lava to the surface. So again, if you can cite a source that woud be helpful.

As background you may want to read the following, so we can be sure we're talking about the same thing:
Radiometric dating - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Radiometric_dating)