The culprit: iceberg sounds
The "bloop" was one of the world's greatest mysteries… until now. This loud deep ocean noise was recorded from several different locations. It followed no known sound forms, and its location could not be pinpointed beyond the general area of the south Pacific ocean off the coast of South America. This ultra-low-frequency sound was extremely loud, carrying for hundreds of miles underwater.
The bloop has long held cult status. Animal Planet famously used the "bloop" as a plot point in their mockumentary "Mermaids: The Body Found." It was used in the initial viral marketing for the movie "Cloverfield." And many people speculated tongue-in-cheek that the bloop was the sound of Cthulhu awakening from his watery slumber.
The sound was heard several times in 1997, and never again… until now.
The U. S. National Oceanic and Atmospheric Administration (NOAA) as part of its acoustics monitoring program has analyzed the bloop in comparison with recent recordings, and determined that it is the sound of an icequake.
An icequake is just like an earthquake, but in an iceberg instead of the planet's crust. Technically called a "non-tectonic seismic event," icequakes usually occur when a glacier or iceberg shifts suddenly. Icebergs and glaciers are colossally heavy, and when the ice shifts off a patch of land, the earth's crust rebounds upwards.
NOAA has hydrophones scattered throughout the world's oceans. In early 2008 their hydrophones in Scotia Sea recorded the sounds as an iceberg dubbed A53a disintegrated. This iceberg experienced multiple icequakes as the gargantuan object fractured, crumbled, split, and eventually shuddered to pieces. And NOAA has determined that the sounds recorded during that iceberg's death are a match on the spectrogram for the bloop.
NOAA is even able to speculate on which iceberg actually generated the bloop. When the bloop was recorded, icebergs between Bransfield Straits and the Ross Sea were in the process of disintegrating. (It might also have been a large iceberg at Cape Adare.)
Not to sound fatalistic, but in hindsight it was only a matter of time before the sound was re-recorded and analyzed. The world's icebergs are disintegrating at an increasingly rapid rate. And it's lucky that we were able to identify the bloop before all of the icebergs were gone. If NOAA scientists had not done the analysis work to cross-reference the bloop with current icequake recordings, it's possible that it would have remained a mystery forever. (Spoilsports!) (I kid.)