In 1997, an ultra-low frequency sound, unlike any heard before, emerged from the deep ocean. Detected by the U.S. National Oceanic and Atmospheric Administration (NOAA), this mysterious noise quickly became known as “the Bloop.” Its enigmatic nature captured public imagination.
The Bloop’s Discovery
The Bloop was first recorded in 1997 by NOAA’s autonomous hydrophone array, a system of underwater microphones deployed in the equatorial Pacific Ocean. This array, designed to monitor seismic activity and marine mammal sounds, picked up the immense noise. Its origin was roughly triangulated to 50°S 100°W, west of the southern tip of South America. The sound was characterized by its ultra-low frequency and high amplitude, indicating significant power. It was loud enough to be detected by sensors over 5,000 kilometers away and notably rose in frequency over approximately one minute.
Initial Speculation
The unusual characteristics of the Bloop immediately fueled various theories regarding its source. Many speculated about a colossal, unknown sea creature, due to the sound’s biological-like profile when sped up for human hearing. The sheer volume of the sound, however, suggested a creature far exceeding the size of any known marine animal, including the blue whale. Other possibilities considered included natural phenomena such as underwater volcanic activity or gas vents, along with human-made sources like military exercises or ship engines, reflecting the broad range of initial investigations.
The Scientific Investigation
NOAA and other researchers embarked on a rigorous scientific process to identify the Bloop’s source, employing triangulation with multiple hydrophones. This data-driven approach systematically ruled out various initial theories. Biological sources were eliminated because the sound patterns did not align with known marine life, and its immense power far exceeded what any creature could produce. Robert Dziak, a seismologist with NOAA and Oregon State University, highlighted that while the sped-up sound resembled an animal vocalization, the real-time recording had a “quake” like quality. Geological events like volcanoes or earthquakes were also ruled out due to an absence of corresponding seismic activity.
The True Source
After years of investigation, the Bloop was identified as an icequake, also known as a cryoseism. An icequake is the sound produced by large ice masses, such as icebergs, fracturing, cracking, or scraping the seafloor, typically originating from glacial ice in Antarctica. These events generate powerful, low-frequency sounds because of the immense scale of the ice involved and water’s efficient propagation over vast distances. Since the Bloop’s initial detection, similar sounds have been recorded, particularly from the fracturing and movement of icebergs, solidifying this identification.