The Enigmatic Sound
In 1997, the U.S. National Oceanic and Atmospheric Administration (NOAA) detected an unusual and powerful underwater sound, which they nicknamed “The Bloop.” This sound captured public interest due to its mysterious nature and immense scale. Scientists recorded the Bloop in the remote South Pacific Ocean, west of the southern tip of South America, making its origin particularly perplexing.
The Bloop was an ultra-low frequency, high-amplitude sound, a very deep, incredibly loud sound. It lasted for about a minute, and its sheer power allowed it to be detected by hydrophones that were thousands of miles apart. These hydrophones were part of the Equatorial Pacific Ocean autonomous hydrophone array, a system designed by NOAA’s Pacific Marine Environmental Laboratory (PMEL) to monitor undersea seismic activity, ice noise, and marine mammal populations. The system augmented the U.S. Navy’s Sound Surveillance System (SOSUS), originally created to track submarines.
The sound’s pattern was unlike any known biological sound. While some marine animals, like whales, produce low-frequency sounds, the Bloop’s amplitude was far greater than anything a known creature could generate. Its detection across such vast distances made it one of the loudest underwater sounds ever recorded.
Initial Hypotheses
The unusual characteristics of the Bloop immediately sparked widespread speculation about its source. Given the sound’s immense power and the vast, unexplored nature of the deep ocean, many people began to consider imaginative theories. The idea that the Bloop could be an unknown, massive deep-sea creature quickly gained traction among the public.
This “sea monster” theory resonated with public fascination, fueling discussions across various platforms. The sound’s deep, varying frequency seemed to mimic biological calls, further supporting the notion of an animal origin, despite its unprecedented loudness. Scientists, including NOAA’s Christopher Fox, acknowledged that while the sound had a profile similar to biological signals, its sheer amplitude meant it would have to come from an animal far more powerful than any known on Earth.
The Scientific Resolution
NOAA scientists continued to investigate the Bloop, analyzing the sound and comparing it to other recorded ocean phenomena. Through this ongoing research, they determined that the Bloop’s true origin lay in natural geological events. The sound was identified as consistent with large icequakes, seismic events caused by the fracturing and movement of massive ice formations.
These powerful icequakes occur when large chunks of ice break off from glaciers or ice shelves, a process known as calving. The sudden stress and fracturing within the ice can generate extremely powerful, low-frequency sounds that travel vast distances through the ocean. Researchers found that numerous icequakes detected in the Antarctic region shared spectrograms and amplitudes very similar to the Bloop. The location of the Bloop’s detection, roughly triangulated to an area in the South Pacific near Antarctica, also supported this conclusion.
By 2005, NOAA definitively attributed the Bloop to these cryoseisms. For instance, icequakes produced during the disintegration of iceberg A53a in 2008 demonstrated similar acoustic signatures and ranges exceeding 5,000 kilometers. While the exact iceberg responsible for the original Bloop remains unidentified, the scientific consensus is that it was the sound of a very large Antarctic ice shelf breaking apart.