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investigate further. It would take a digital seismo-
graph—as opposed to Oliver’s analog paper and
ink machines—to bring the pulse back into focus
some 43 years later. In 2005, a graduate student at
the University of Colorado, Boulder, presented data
reintroducing the bizarre blip no one could explain.
Since then, scientists have been listening to the
pulse but have only gotten as far as identifying its
point of origin: shallow waters called the Bight of
Bonny, off the coasts of Nigeria and Cameroon.
Some researchers believe the pulse is caused by
the ocean. The world’s continental shelves—the
boundary where shallow coastal waters quickly
drop miles down to the ocean’s abyssal plain—act
as a gigantic wave break. Scientists have theorized
that as waves hit a specific place on the continen-
tal shelf in the Gulf of Guinea, this regular pulse
is produced.
If that sounds improbable, consider all the dif-
ferent shapes of drums, from timpani to bass
drums to bongos. It’s not impossible that just one
shape of continental shelf “drum” would create the
right harmonic bang to rattle the Earth. If that’s
true, we’re probably lucky it’s just one.
But what if it’s not a huge wave crash that causes
the pulse to blip? According to Dork Sahagian,
Ph.D., a professor of Earth and environmental sci-
ence at Pennsylvania’s Lehigh University, you have
to consider what might cause the pulse when “there
are no nearby storms to make the waves that inter-
act with the continental shelves and coasts.”
In the event that nothing churns the ocean’s
waters enough to create a large impact against
a continental shelf, Sahagian says perhaps vol-
canoes, like the ones in the Cameroon line that
extend into the Bight of Bonny, are responsible.
“So does the microseismicity come from the vol-
canic eruptions and tremors directly, or does the
volcanic activity generate ocean waves that then
interact with the coast to cause the 26-second
pulse? I suspect the latter,” he says. But other
researchers think the cause is a volcano on São
Tomé Island in the Bight of Bonny because of its
close proximity to the origin point of the micro-
seism. This theory is supported by the fact that
there’s a similar volcanic microseism that’s well
documented in Japan.
This mystery pulse is a good reminder that so
much remains to be discovered. Scientists have
studied the pulse and debated its origin, but itjust hasn’t reached a tipping point of interest to
be solved—yet. This is most likely due to other
research efforts taking precedence.
For instance, seismologists have had the
opportunity to analyze new data, thanks to a
50 percent reduction in high-frequency noise
caused by human activity since the COVID-19
pandemic began.
That could mean they all redouble efforts on
high-priority subjects. “There are many other
mysteries in need of solution,” Sahagian says. For
example, how will geoengineering impact Earth’s
climate and ecosystems?
Even so, it’s still possible that the right person
at the right time will be listening and finally figure
out what’s causing the 26-second chirp once and for
all. In a perfect world, we’d have answers to these
big questions and the small nagging ones, too.FAIRY CIRCLES.
In the Namibian desert, bare
patches of dirt are surrounded
by grass, creating a spotted
pattern when seen from
above. It’s theorized that the
patches are the result of plants
competing for access to water,
or that these barren pieces of
earth are caused by termites
who clear portions of land for
their nests. Either theory could
be correct. And some scientists
even posit that the circles are
caused by both plants and
termites.—Daisy HernandezMIMA MOUNDS.
These natural formations, which
often look like small, oval hills
protruding from the ground, are
found in Washington State, Cali-
fornia, and several other spots
around the world. Researchers
believe they’re caused by gener-
ations of gophers. The animals
are incredibly territorial and
the mounds are approximately
the same size as an individual
gopher’s territorial range. While
evidence supports this theory,
how the mounds rise from the
ground remains unknown.More Unexplained Geological
Phenomena