Occasionally, mysterious events arise that capture the public’s attention. Whether it’s a UFO sighting, strange tracks in the forest, or an eerie sound in the dead of night, curiosity and fear often blend together quickly.
When that happens, people’s imaginations tend to run wild, sparking all sorts of speculative theories. This is exactly what occurred when a peculiar “bloop” sound was detected in the Pacific Ocean in 1997. After years of speculation and debate, scientists eventually unravelled the mystery behind it.
An Unexpected Discovery.
Researchers from the National Oceanic and Atmospheric Administration (NOAA) had positioned underwater microphones, known as hydrophones, across the southern Pacific Ocean. These devices were initially designed to monitor underwater volcanic activity, particularly in Antarctic regions.
The Mysterious Sound.
However, in 1997, the hydrophones recorded something unusual. As reported by Wired, they detected an extraordinarily loud, ultra-low frequency sound. This “bloop” was so powerful that hydrophones located more than 3,000 miles apart were able to capture it, sparking widespread intrigue.
An Unfamiliar Sound.
Researchers recorded several occurrences of a mysterious, loud noise, but its distinctive nature made it difficult to describe as anything other than the “bloop.” For nearly a decade, this baffling sound puzzled experts, as nothing like it had ever been captured before.
A Challenging Mystery.
Scientists at NOAA’s Pacific Marine Environmental Laboratory (PMEL) were intrigued by the strange sound and eager to uncover its source, but the task was anything but simple. With over 95% of the world’s ocean depths still unexplored by humans, identifying the origin of the “bloop” was like searching for a very loud needle in an enormous underwater haystack.
Public Fascination with the “Bloop”.
As Wired reported, once the public became aware of the “bloop” in the years following its discovery, a range of intriguing theories began to surface. Media outlets fueled speculation by suggesting the sound had an “organic” origin, which only heightened public curiosity.
The Leading Theory.
Because the noise was described as “organic,” the most widely accepted theory was that the “bloop” was produced by a massive, undiscovered sea creature. This idea gained traction, especially given that new species continue to be found, even decades after the sound was first detected.
The Stuff of Legends.
According to NOAA, one early theory about the mysterious “bloop” sound was that it came from a giant squid. However, for this to be the case, the squid would have to be of an unimaginable size, reminiscent of something from 20,000 Leagues Under the Sea.
A Slightly More Plausible Idea.
Another popular theory pointed to a massive whale as the source of the sound. Since the oceans are home to enormous species like the blue whale, it wasn’t entirely far-fetched. However, for this theory to hold, the whale would need to make a sound that had never been observed before. Alternatively, it could suggest the existence of an even larger, undiscovered whale species.
The Most Outlandish Hypothesis.
For those unsatisfied with these explanations but still convinced that the “bloop” originated from a living creature, some began to entertain more creative ideas. These speculations often centred on a yet-to-be-discovered sea creature, as NOAA suggested, one “unknown to science.”
Only Half-Kidding.
As reported by Wired, some fans of horror fiction were quick to note that the location of the “bloop” was just over 1,000 miles away from where author H.P. Lovecraft imagined the sunken city of R’lyeh.
In Lovecraft’s mythology, this is where the legendary monster Cthulhu is said to lie dormant. Although most fans weren’t seriously proposing that the creature had awakened, it was a compelling and eerie connection.
Alternate Theories Begin to Surface,
While many were drawn to the idea of the sound originating from an unknown sea creature, others believed a more grounded explanation was possible.
Instead of an undiscovered species, some theorised the “bloop” was the result of a secret underwater experiment conducted by one of the world’s military forces.
This theory offered an intriguing alternative without the need for mythical monsters or massive undiscovered animals.
Far More Mundane Explanations.
According to the National Oceanic and Atmospheric Administration (NOAA), more common vessels could have been the source of the mysterious “bloop” sound. Some suggested that it might have been caused by ship engines or even fishing boat winches.
However, these theories seem far-fetched when considering the sheer volume and reach of the sound, which far exceeded the noise levels typically produced by such machinery.
Fun Speculation, but Nothing More.
In an interview with Wired, NOAA seismologist Robert Dziak emphasised that no serious researcher believed a giant creature was behind the “bloop.” He explained that public misconceptions arose from other factors that led to the more imaginative theories.
A Misleading Edit.
Dziak told Wired, “What has led to a lot of the misperception of the animal origin of the Bloop is how the sound is played back.” The sound the public often hears is roughly 16 times faster than the original recording, giving it the eerie, animal-like quality people associate with the mystery.
A Deep, Rumbling Noise.
When played back at its normal speed, the “bloop” is less of a strange, high-pitched cry and more of a deep rumble, resembling an earthquake or rolling thunder. For NOAA scientists, this pointed to a more likely explanation: a natural process was behind the sound. The challenge was determining exactly what that process was.
Rare but Notable.
What made the “bloop” particularly intriguing for researchers was that it’s rare for NOAA’s hydrophones to capture an unfamiliar sound. According to Dziak, most sounds fall into one of five categories: geophysical (like earthquakes), anthropogenic (human-made sounds), ice, weather, or animals.
Rare Exceptions.
Weather, ice, and animal sounds are fairly straightforward, while geophysical noises typically refer to events like underwater volcanic eruptions or earthquakes. Anthropogenic sounds are human-made, such as those produced by ships. Anything outside these categories is usually dismissed as electronic interference, Dziak explained.
The Search Begins.
When the mysterious “bloop” sound was first detected, it was unclear which category it belonged to, if any. In response, researchers from the Pacific Marine Environmental Laboratory (PMEL) deployed additional hydrophones in the region where the sound was first heard.
However, according to the NOAA, the primary goal of these devices wasn’t to track down the source of the sound, but to study underwater volcanic and seismic activity.
Getting Closer to the Truth.
As more hydrophones were placed closer to Antarctica, researchers found themselves inching closer to solving the mystery of the “bloop.” By 2005, a significant clue finally emerged.
Listening in Detail.
In an interview with Wired, Robert Dziak, a NOAA researcher, explained that they focused closely on the acoustic data gathered from the Bransfield Strait and the Drake Passage. These regions are near the northwestern tip of Antarctica, and the sounds recorded there were part of what Dziak referred to as an “acoustic survey.”
A Perfect Match.
The NOAA’s acoustic survey ran from 2005 to 2010. By the end of the study, researchers were confident that they had identified the same sounds that baffled scientists in 1997. According to Dziak, the sounds were strikingly similar to the “bloop” in both frequency and duration.
The Mystery Solved.
Thanks to the increased use of monitoring equipment, identifying the source of these unusual noises became much easier. The NOAA concluded that the mysterious “bloop” sound heard in 1997 was, in fact, the result of an icequake.
What Is an Icequake?
An icequake, as described by the NOAA, refers to the noise and vibrations caused when an iceberg breaks off from a glacier. Since icequakes were occurring during NOAA’s acoustic survey, it became clear that a similar event likely produced the “bloop” sound originally detected by hydrophones in 1997.
A Sleeping Giant Awakened.
Uncovering the source of the mysterious “bloop” was undoubtedly satisfying, but the acoustic analysis revealed even more than anticipated. According to Dziak, “It became clear that the sounds of ice breaking up and cracking are the dominant source of exact natural sounds in the Southern Ocean.”
More Common Than Expected.
Though it took years to identify what an ice quake sounds like, such events are actually quite frequent in polar regions. As Dziak explained, “Each year, tens of thousands of what we call ‘icequakes’ occur due to the cracking & melting of sea ice and glaciers calving into the ocean. These signals are strikingly similar to the Bloop.”
An Increasing Phenomenon.
The NOAA reports that icequakes have been growing more frequent in recent decades, a clear sign of the effects of global climate change. As glaciers melt at a faster pace, icebergs break off more often, eventually melting into the sea.
Debunking the Wilder Theories.
Though some speculated that the Bloop might be evidence of an undiscovered sea monster or secret military activity, NOAA scientists always found those theories implausible. Once the ice quake sounds were compared to the Bloop, it became clear that there was little chance of another explanation.
A Long-Suspected Answer.
Dziak revealed to Wired that the PMEL team, which solved the mystery of the Bloop’s origin, was eager to confirm its source, though the outcome wasn’t entirely surprising. For years, NOAA had suspected the sound was linked to naturally occurring ice breaking.
A Mystery Solved, Yet Still Fascinating.
For some, learning that the truth wasn’t as fantastical as they had hoped may have been a letdown. Still, there’s a sense of satisfaction in solving any mystery. Barring any unforeseen developments, this particular enigma is now considered resolved.
MEL’s Ongoing Mission.
Even without many decade-long mysteries like the Bloop, PMEL’s Acoustics Program continues to develop technology to capture and analyse long-term data on oceanic sounds. As the Bloop case demonstrates, these sounds offer valuable insights into how human activities and natural forces shape marine environments.
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