On the other hand, the main period of about 30 Myr is close to the Solar System’s ~ 32 ± 3 Myr vertical oscillation about the mid-plane of the Galaxy. In the Galactic plane region, increased cosmic-ray flux might lead to significant climatic changes, whereas encounters with concentrations of disk-dark matter might trigger comet showers from the Oort Cloud, as well as thermal and geophysical disturbances in the inner Earth. We note that a 26 to 37 Myr cycle has been reported in the ages of terrestrial impact craters, using various statistical techniques and sets of crater ages potentially connecting the terrestrial and extraterrestrial cycles.
Of course, figuring out the mechanism that causes the pattern comes after establishing that the pattern itself is real. As I pointed out in my post on the Ganzfeld Experiment a couple of weeks ago, developing a model to explain a phenomenon has to wait until you've shown that there's a phenomenon there to explain.
But a 96% confidence level is enough to indicate that there's some underlying mechanism at work here that's worth further study. Something, apparently, is causing a strange, regular pulse of catastrophes. (To put your minds at ease -- I know this was one of the first things I wondered -- the last peak the analysis found occurred 12.1 million years ago, so we've got another fifteen-odd million years to go before the next one. That is, if we don't manufacture a cataclysm ourselves first.)
For now, all we have is an odd, unexplained pattern in geological upheavals. It will be fascinating to see what refinements are put on the analysis -- and whether the scientists can find out what's actually going on. Until then, we're left with a mystery -- a 27.5 million year terrestrial heartbeat.