The idea of colossal, unknown creatures in the deep ocean has long captured human imagination. In 1997, a mysterious, ultra-low-frequency sound recorded in the remote South Pacific fueled this speculation, leading to the widespread public query: is the “Bloop Fish” real? This powerful acoustic anomaly, nicknamed “the Bloop,” was intense and unlike any known vocalization. The noise was real, but its origin points not to an undiscovered monster, but to one of the planet’s most powerful natural forces.
The Initial Detection of the Bloop
The sound was first registered by the U.S. National Oceanic and Atmospheric Administration (NOAA) using an Equatorial Pacific Ocean autonomous hydrophone array. This specialized network of underwater microphones was deployed to monitor deep-sea seismic activity, hydrothermal vents, and marine mammal populations. The Bloop was an ultra-low frequency sound, below the range of human hearing, and lasted for approximately one minute.
The sheer power of the sound set it apart from typical ocean noise. NOAA’s hydrophones, placed thousands of miles apart, recorded the Bloop across a distance exceeding 5,000 kilometers (about 3,100 miles) in the South Pacific Ocean. Triangulation placed the source near 50°S 100°W, west of the southern tip of South America.
The Theory of a Biological Origin
Initial speculation regarding the Bloop’s source leaned toward a biological entity due to its frequency characteristics. Scientists noted that the sound exhibited a rapid variation in frequency, a pattern often seen in the vocalizations of large marine mammals, such as the blue whale. The pattern suggested a pulsing, almost organic sound source, which led some researchers to consider an animal origin.
The problem, however, was the incredible volume of the sound. To be detected by sensors over such a vast distance, the Bloop would have had to be several times louder than the loudest sound produced by any known animal, including the mighty blue whale. This fact naturally led to the hypothesis of a creature far larger than any previously recorded marine species.
The public fascination with a “bloop fish” or “sea monster” grew precisely because the scientific data pointed toward a biological pattern, yet the amplitude was astronomically higher than anything observable. The discrepancy between the sound’s biological characteristics and its extreme power kept the mystery alive for several years.
The Scientific Explanation
The mystery of the Bloop was ultimately resolved when NOAA scientists began a more focused study of the deep Southern Ocean. Researchers deployed hydrophones closer to Antarctica to monitor the sounds produced by glacial movements. They were able to capture numerous instances of sounds known as “icequakes.”
Icequakes are generated by the intense fracturing and cracking of massive icebergs as they break away from Antarctic glaciers, a process called calving. The unique characteristics of these cryoseisms—specifically their ultra-low frequency, high amplitude, and rising frequency spectrogram—were determined to be a near-perfect match for the Bloop. The immense size of the icebergs and the distance the sound travels through the water’s natural sound channels fully account for the Bloop’s colossal volume and wide detection range.
Further analysis confirmed that the Bloop was consistent with the vibrational patterns generated by the movement and disintegration of large ice masses. The scientific conclusion definitively established that the sound was a natural, non-biological phenomenon, effectively debunking the popular “bloop fish” theory.
Other Unidentified Ocean Sounds
The Bloop is not the only strange acoustic event to be recorded by NOAA’s deep-sea monitoring systems. The vast, deep ocean is a naturally noisy environment, and scientists routinely detect sounds that require investigation. Other formerly unidentified sounds include “Julia,” “Slow Down,” and “Upsweep.”
Julia, recorded in 1999, was another powerful sound later attributed to a large Antarctic iceberg running aground and scraping the seafloor. “Upsweep” has been recorded seasonally since 1991 and consists of a long series of narrow-band, upsweeping sounds. The origin of the Upsweep is still uncertain, though it is speculated to be related to underwater volcanic activity in the Pacific. These events illustrate that the deep ocean continues to produce acoustic enigmas that challenge researchers.