Scientists puzzled by Earth's 'heartbeat' that triggers little tremors every 26 seconds

To the average person standing on the ground, the planet feels solid and still. But to a seismologist watching the data, the Earth is constantly moving, humming with a rhythmic pulse that has baffled scientists for over 60 years.

Every 26 seconds, like clockwork, a faint seismic tremor ripples through the Earth's crust. Known as a "microseism," it isn't strong enough to knock over a vase, but it is distinct enough to be recorded by monitoring stations on multiple continents.

The mystery began in the early 1960s when geologist Jack Oliver first documented the phenomenon. He managed to trace the pulse to the southern or equatorial Atlantic Ocean, but the technology of the time limited his investigation.

A road near equatorial Atlantic OceanCanva

“Jack didn’t have the resources in 1962 that we had in 2005 — he didn’t have digital seismometers, he was dealing with paper records,” Michael Ritzwoller, a seismologist at the University of Colorado, Boulder, told Discover Magazine.

In the decades since, technology has improved, allowing scientists to triangulate the source more precisely. The pulse appears to originate from a specific location: the Bight of Bonny in the Gulf of Guinea, off the western coast of Africa.

While the "where" is settled, the "why" remains a matter of fierce debate.

In 2013, student Garrett Euler presented a theory at the Seismological Society of America conference, suggesting that the pulse was caused by ocean waves crashing against the continental shelf.

Waves crash against rocksCanva

Lars Eivind Augland, an associate professor at the University of Oslo, explained this theory to Yara International: "Special depth conditions, the geometry of the ocean floor, and the coast have been pointed out as possible causes. Due to how the waves hit and create resonance on the seabed, they could, in turn, propagate as earthquake waves in the Earth's crust."

However, another theory emerged that same year. Yingjie Xia of the Institute of Geodesy and Geophysics in Wuhan argued that the source was actually a volcano on the island of São Tomé, located near the pulse's epicenter.

Recently, a third, more complex theory has gained traction. "A third explanation can be found in the latest study published in the renowned journal Earth and Planetary Science Letters, which states that fluid flowing through fractal fissure networks in sediments under the seafloor is the cause of the tremors," Augland noted.

Despite these competing hypotheses, Augland specified that none have been definitively proven. For now, the Earth continues its mysterious, 26-second rhythm, keeping its secrets buried deep beneath the ocean floor.

Earth's heartbeat, microseisms, 26-second pulse, seismology, Bight of Bonny, Jack Oliver, geological mystery, Gulf of Guinea, seismic tremors, Earth science YouTube