In 1997, researchers at the National Oceanic and Atmospheric Administration (NOAA) were supposedly baffled when they heard a very loud, ultra-low frequency sound of unknown origin in the southern Pacific Ocean. The sound was registered when they were listening for volcanic activity using an array of underwater microphones (hydrophones) designed by NOAA’s Pacific Marine Environmental Laboratory (PMEL).

Nicknamed the “Bloop,” the sound was apparently so loud that it was heard by hydrophones placed over 5,000 kilometers (3,000 miles) apart across the Pacific. Its source was roughly triangulated to coordinates 50°S 100°W, a remote region beyond the tip of South America.

The Explosion of Mysterious Creature Theories

As its source was not known, the Bloop attained the status of an unsolved mystery attracting many theorists and speculations that it could have been made by a sea creature as yet unknown to humankind. Considering the water world is far less explored than the land, less than 5% as much, according to NOAA, many even believed that might be the case.

Some horror fiction enthusiasts went a little further and pointed out that the location the sound came from is close to the sunken city of R’lyeh, a fictional lost city from H. P. Lovecraft’s shared fictional universe, The Cthulhu Mythos, where the creature Cthulhu was imprisoned.

What Could Be the Bloop’s Source?

However, according to seismologist Robert Dziak from Oregon State University and  NOAA, the Bloop was actually made by ice breaking off and cracking. Anyone with any knowledge of marine geophysics or geology would know there are rarely any mysteries regarding sounds in the oceans. They are either geophysical, which is caused by volcanoes or earthquakes on the ocean floor, weather related, man-made, such as sounds from ships and airguns, marine life, or caused by ice due to quakes or calving.

What Are “Icequakes” and “Ice Calving”?

“Icequakes” occur when water in the ground freezes rapidly, causing a sudden cracking of frozen soil or rock when the ground is saturated with water. There has been an increase in the number of icequakes in Antarctica as the increase in temperatures melts the glacial ice.

But when the temperature drops at night, the water freezes quickly, and the stress built from freezing is released explosively. Since they do not happen due to movements in tectonic plates, they are referred to as non-tectonic seismic events.

“Ice calving,” on the other hand, occurs when deep cracks form in the glaciers due to stresses and cause a part of it up to 60 meters (200 feet) high to break off from the edge and fall into the ocean. The broken pieces are then icebergs. Calving generates very loud cracking or booming noise, and the resulting waves are often hazardous.

With global warming causing the polar ice caps to melt, ice calving and icequakes have become increasingly common phenomena. In fact, the glaciers of Greenland alone create 12,000 to 15,000 icebergs every year due to calving.

Researchers Solve the Mystery of the Bloop

Following a 2005-2010 acoustic survey of the Bransfield Strait and Drake Passage, the oceanic area between the tip of South America and Antarctica, NOAA found that the dominant source of natural sounds in the southern oceanic regions of our planet are the sounds of ice cracking and breaking up. Every year, tens of thousands of these sounds occur as the ice melts and breaks or cracks, and the Bloop sound signature matches these sounds.

Besides, the sound that is popularly heard by the world is usually played 16 times faster than the actual recorded sound, which was part of the reason so many wanted to believe it to be a mysterious creature. When played at its actual speed, it sounds more like a quake, proving all creature theories to be fantasies.