The Bloop: Mystery Sound from the Deep

In the summer of 1997, the National Oceanic and Atmospheric Administration detected something strange in the deep waters of the South Pacific. An ultra-low frequency sound, one of the loudest ever recorded in the ocean, was picked up by underwater microphones thousands of miles apart. The sound, later nicknamed “The Bloop,” has never been definitively explained, though official sources now attribute it to ice breaking. For years, however, the Bloop fueled speculation about massive unknown creatures lurking in the ocean depths.

The Detection

NOAA operates a network of hydrophones, underwater microphones originally developed during the Cold War to detect Soviet submarine activity. After the Cold War ended, these hydrophones were repurposed for oceanic research, including the study of whale communications, underwater volcanic activity, and other marine phenomena.

In 1997, sensors detected an unusual sound at several monitoring stations across the Pacific. The sound was extremely powerful, so powerful that it was picked up by sensors nearly 5,000 kilometers apart. Scientists estimated the source was located in a remote area of the South Pacific, roughly 50 degrees south latitude and 100 degrees west longitude, west of the southern tip of South America.

The sound was dubbed “The Bloop” by NOAA researchers because of its unique acoustic profile, a rapid frequency rise that, when sped up for human hearing, sounded like a “bloop.” The original recording, lasting just over a minute, remains one of the most famous unexplained sounds ever captured.

Characteristics of the Sound

The Bloop was remarkable for several reasons. Its volume was extraordinary, making it one of the loudest sounds ever recorded in the ocean. Sound travels efficiently through water, but for a single source to be detected across such vast distances required enormous power.

The sound’s frequency profile was also unusual. When analyzed by scientists, it did not match any known natural or man-made source. It did not resemble any ship engine, submarine, or underwater drilling operation. It also did not match the vocal signatures of any known marine animal.

The profile did share some characteristics with biological sounds, specifically the calls of large marine animals. This observation led to one of the most intriguing early hypotheses about the Bloop’s origin.

The Giant Animal Theory

When the Bloop was first analyzed, some researchers noted that its acoustic profile was consistent with a biological source, specifically something that might be produced by the sound-making apparatus of an enormous animal. However, there was a significant problem with this hypothesis: the loudness of the sound implied a creature far larger than any known animal on Earth.

The blue whale is the largest animal known to have ever existed, reaching lengths of up to 100 feet and weights of up to 200 tons. Blue whales produce extremely loud vocalizations that can travel across entire ocean basins. Yet the Bloop appeared to be significantly louder than any whale call ever recorded. Whatever made the sound, if it was biological, would need to be considerably larger than a blue whale.

This led to speculation about unknown deep-sea creatures of enormous size. The deep ocean remains largely unexplored, and new species are discovered regularly. Could there be something living in the depths that dwarfs even the great whales? Giant squid were considered mythological until relatively recently, and their larger relatives, the colossal squid, may reach sizes that have not yet been documented.

The deep ocean provides both habitat and food sources that could theoretically support very large organisms. Pressure and darkness at extreme depths create conditions unlike anything on the surface. The possibility that something enormous and unknown lives in these depths cannot be entirely ruled out.

The Official Explanation

In 2012, NOAA announced that the Bloop was consistent with the sounds produced by large icebergs calving and breaking apart. Ice produces powerful low-frequency sounds as it fractures, and these sounds can travel vast distances underwater. The Antarctic ice sheet, which is relatively close to the Bloop’s detected location, regularly produces such events.

NOAA’s analysis compared the Bloop’s acoustic signature to known icequake recordings and found substantial similarities. The case, from the agency’s perspective, was closed. The Bloop was ice, not a monster.

This explanation has been largely accepted by the scientific community. Ice calving events are common, powerful, and capable of producing sounds with the characteristics observed in the Bloop recording. Occam’s razor suggests that a known phenomenon, ice breaking, is more likely than an unknown phenomenon, a creature larger than anything documented.

Lingering Questions

While the ice explanation is considered most likely by mainstream science, some questions remain. The Bloop was detected during the Southern Hemisphere winter when ice calving would be less common. The specific acoustic profile, while similar to ice sounds, was not identical. And the location of the source, while in the general vicinity of Antarctica, was far from any known major ice formations.

Critics of the official explanation note that NOAA did not state definitively that the Bloop was ice, only that it was “consistent with” ice sounds. This careful phrasing leaves room for other possibilities.

The deep ocean remains one of Earth’s last frontiers. Less than 5% of the seafloor has been mapped in detail, and vast regions have never been visited by humans or submersibles. The creatures that live at extreme depths are adapted to conditions that humans can barely imagine. It is not impossible that something unknown produced the Bloop.

Cultural Impact

Regardless of its true origin, the Bloop captured public imagination in ways that few scientific mysteries have. The possibility that something enormous and unknown lurked in the deep ocean touched a primal fear that has haunted humanity since ancient times. The sea has always been a source of legend, from the Kraken to Leviathan, and the Bloop seemed to validate those fears.

The Bloop became a phenomenon on the early internet, discussed in forums and featured on websites dedicated to mysteries and unexplained phenomena. It appeared in video games, fiction, and popular culture references. The sound, sped up to audible range, was played on news broadcasts and radio shows.

Writer H.P. Lovecraft, who set some of his most famous horror stories in the deep sea, was frequently invoked in discussions of the Bloop. Lovecraft’s fictional coordinates for the sunken city of R’lyeh, home of the dreaming god Cthulhu, are relatively close to the Bloop’s detected location, a coincidence that has fueled endless speculation and jokes.

Other Mysterious Sounds

The Bloop was not unique. NOAA’s hydrophone network has detected numerous unexplained sounds over the years, most of which have eventually been attributed to ice, volcanic activity, or other geological processes. Others remain unexplained.

“Slow Down,” detected in 1997, was a sound that gradually decreased in frequency over about seven minutes. “Julia,” also from 1999, sounded like someone talking or whining. “Upsweep” has been detected since 1991 and consists of a series of sounds with rising frequency.

Each of these sounds has sparked its own speculation, though none captured public imagination quite like the Bloop. Together, they demonstrate that the ocean remains full of sounds we do not fully understand, produced by processes we have not witnessed and, perhaps, by creatures we have not discovered.

Conclusion

In the summer of 1997, something in the South Pacific produced one of the loudest sounds ever recorded. It was probably ice. Science says it was ice. The acoustic analysis points to ice.

And yet.

The deep ocean holds mysteries we have not begun to solve. Creatures live in the crushing darkness of the abyssal plains that we have never seen alive. The giant squid was a legend until the 20th century. The megamouth shark, a filter-feeding behemoth growing to nearly 20 feet, was unknown until 1976.

The Bloop was probably ice cracking. But somewhere in the lightless depths of the Pacific, creatures swim and call and hunt that no human has ever observed. The ocean covers 70% of Earth’s surface and reaches depths of nearly 36,000 feet. We have been to the bottom exactly once, briefly, in 1960.

We do not know everything that lives down there. We do not know everything that calls in the darkness. And when a hydrophone captures a sound that does not quite match anything in the database, a sound of immense power from the remote reaches of the sea, it is worth remembering that our knowledge of the ocean is still profoundly incomplete.

The Bloop was probably ice. But the deep ocean keeps its secrets.