A Global Seismic Beat No One Can Explain
Every 26 seconds, Earth shakes. The movement is too subtle for people to feel, yet sensitive instruments around the world register it like clockwork. First documented more than 60 years ago, this regular “pulse” remains unexplained despite decades of research and debate among scientists.
The First Clues in the 1960s
In the early 1960s, geologist Jack Oliver at the Lamont-Doherty Geological Observatory detected the strange rhythm while studying seismographic records.
Working with paper instruments, Oliver traced the pulse to somewhere in the southern or equatorial Atlantic Ocean. He noted that the signal grew stronger during Northern Hemisphere summers.
Rediscovery and Triangulation
The mystery resurfaced in 2005 when graduate student Greg Bensen at the University of Colorado Boulder noticed a clear, repeating signal in seismic data. Along with his colleagues Mike Ritzwoller and Nikolai Shapiro, he verified that the pulse was real, not an instrument error.
Using modern digital seismometers, the team triangulated its origin to the Gulf of Guinea, off the western coast of Africa. Their findings echoed Oliver’s earlier work.
Competing Theories
Scientists have proposed several explanations. In 1980, Gary Holcomb of the U.S. Geological Survey linked the pulse to storm activity. Later studies focused on ocean waves hitting the continental shelf in the Gulf of Guinea, deforming the seafloor and producing seismic energy. In 2013, graduate student Garrett Euler pinpointed the source to the Bight of Bonny and argued that wave interactions were the most likely cause.
Not all researchers agree. That same year, Yingjie Xia and his team at the Institute of Geodesy and Geophysics in Wuhan, China, suggested the nearby volcano on São Tomé island might be responsible. Similar volcanic microseisms have been documented at Japan’s Aso Volcano, lending weight to this hypothesis.
A Mystery That Endures
Despite these efforts, no single explanation has been confirmed. The phenomenon’s persistence raises further questions. Many other continental shelves and volcanoes exist worldwide, yet none are known to produce a comparable regular seismic beat. Researchers acknowledge that the pulse remains a lower priority compared to other seismic studies, which may explain the slow progress.
Nearly six decades after Jack Oliver’s discovery, the 26-second pulse continues to reverberate through the planet and elude definitive explanation.
Every 26 seconds Earth shakes, too faint to feel, yet recorded worldwide.
First logged in the 1960s, the steady beat has no confirmed cause.
A decades long mystery hums underfoot, and scientists still argue about what drives the clocklike pulse…🧵👇 pic.twitter.com/vFY26eEwkE
— Fascinating True Stories (@FascinatingTrue) October 10, 2025