Every 26 seconds, the Earth’s crust resonates softly, akin to the rhythmic beating of a heart or the steady ticking of a clock.
These faint seismic events, termed “microearthquakes,” are imperceptible to the human senses, yet they are captured by the sensitive instruments used by seismologists.
Although scientists identified this consistent pulse decades ago, a definitive cause remains elusive.
Microearthquakes occur more frequently than one might think, arising from natural events on Earth, such as ocean waves crashing against shorelines or sports enthusiasts rhythmically stomping their feet.
They contribute to a sort of seismic background noise. Yet, this particular microearthquake is distinctive due to its persistent and rhythmic quality.
Dr. Jack Oliver, a geologist from Columbia University, played a key role in recognizing this global storm of microearthquakes, noting that the source was located in the southern Atlantic Ocean.
Now, over fifty years later, advancements in technology have allowed scientists to more precisely locate its origin.
These studies reveal that the pulse originates from Bonny Bay, situated in the Gulf of Guinea off the west coast of Africa.
Researchers have narrowed down the cause to two primary theories: ocean waves or volcanic activity.
Intense waves reflecting off the coast of Africa might converge at a specific location near Bioko Island.
When these waves strike the continental shelf, their energy can slightly bend the Earth’s crust, resulting in regular seismic waves.
Significantly, the strength of the 26-second pulse appears to correlate with storm intensity in the southern Atlantic, meaning that as storms escalate, so do the waves and the resulting seismic energy.
Conversely, Chinese researchers suggest that a volcano on Sao Tome Island may be responsible for these seismic pulses. Previous studies have linked volcanoes to microseismic activity as well.
For instance, Mount Aso in Japan is known to cause tremors believed to result from gas and magma movement underground.
Additional research has uncovered a second source of periodic microseismic activity from the same region, oscillating at a slightly different frequency of every 28 seconds.
This pulse seemingly originates near Pico Cao Grande, another volcano on Sao Tome Island.
This implies that the 28-second pulse could be volcanic in nature, while the 26-second pulse might stem from another undiscovered volcano.
Despite these intriguing findings, the exact cause of Earth’s seismic pulse continues to remain a mystery.
While this pulse’s consistency is fascinating, it doesn’t pose any danger, making it a relatively low-priority area for further seismological research.
It’s my hope that we uncover answers soon.
This article addresses the question posed by Patrick Hawkins via email: “Does the Earth have a heartbeat?”
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