Scientists from New York University and the Carnegie Institution of Science analyzed 89 major geological events from the past 260 million years—everything from mass extinctions to volcanic activity, sea-level fluctuations to continental plate shifts.

And far from being totally arbitrary, these large-scale upheavals seem to come in pulses. These cataclysmic events seem to be grouped into 10 clusters, occurring every 27.5 million years or so.
Like an extremely slow heart rate. A pulse, if you will.

And this means that geological events, like the movement of continental plates or volcanic eruptions, may actually be tied to something, and may even be influencing each other.