Hi et -

My guess right now, and this will remain a guess until detailed tree ring analysis is available for the volcanic eruptions, is that they occured just after 410 CE, as the native records state. If so, no doubt they led to the ensuing climate collapse which led to an initial outbreak of the plague, and the initial germanic migrations -

The 536 CE collapse appears to have been due to cometary dust, but as NASA simply does not give a rat's ass about you or anyone else living on this planet dying from small to medium impacts, it will undoubtedly be quite a while before the cause of these disasters is cleared up.

ep