[Vaduz]

Nope quakes have a cycle too.

[Errant]

It's my belief also, that earthquakes occur in cycles. I put together a little chart based on USGS data (below), that I think demonstrates that earthquakes do occur in cycles. I'm not too sure about the time frame, though 15 years works somewhat in the chart, based on a VERY tiny amount of data.

Your initial question concerned volcanic cycles. It's obvious, however, the two are certainly related. The question is which one drives the other; or, what is the amount of synergy taking place?

[Errant]

I think I see an 11 year cycle in the earthquake chart above, that seems to line up with this solar cycle chart below?