From Discover:
Every 26 seconds, the Earth shakes. Not a lot — certainly not enough that you’d feel it — but just enough that seismologists on multiple continents get a measurable little “blip” on their detectors. But even though this pulse has been observed for decades, researchers don’t agree on what’s causing it. The mystery surrounding the phenomenon even has its own XKCD web comic.
The pulse — or “microseism” in geologist lingo — was first documented in the early 1960s by a researcher named Jack Oliver, then at the Lamont-Doherty Geological Observatory. He’s best known for his later work that supplied some important early evidence for shifting tectonic plates. Oliver figured out that the pulse was coming from somewhere “in the southern or equatorial Atlantic Ocean” and that it was stronger in the Northern Hemisphere’s summer months (or, the Southern Hemisphere’s winter).
And so what’s going on?
Perplexed, the team [Greg Bensen, Nikolai Shapiro] examined the blips from every possible angle. Was something wrong with their instruments? Or their analyses? Or was this seismic activity really happening? All signs pointed to the latter. They were even able to triangulate the pulse to its origin: A single source in the Gulf of Guinea, off the western coast of Africa. They dug up Oliver’s and Holcomb’s work, too, and published a study in 2006 in Geophysical Research Letters. But even since then, no one has really confirmed the cause of the regular seismic activity. Though many assume it’s caused by waves, some hold out that it’s caused by volcanic activity.
Yeah, we don’t know. And that’s what makes this fascinating. Waves? Volcano on a ridiculous timer?
Alien spaceship? No, of course not. That’d be too easy.
I hope they figure this out sometime soon. It makes my toes curl just thinking about it.
