A Sound from the Deep

In the summer of 1997, a network of underwater microphones in the southern Pacific Ocean detected a remarkable sound. The U.S. National Oceanic and Atmospheric Administration (NOAA) had placed the hydrophone array, originally designed to detect Soviet submarines, to monitor undersea volcanic activity. Instead, it recorded an ultra-low-frequency rumble that was extremely loud and had a unique auditory signature, which scientists nicknamed "The Bloop". The sound, which rose in frequency for about a minute, was of sufficient amplitude to be heard on multiple sensors over 5,000 kilometers (3,100 miles) apart.

The sheer volume of the sound was puzzling. It was far more powerful than the vocalizations of any known animal on Earth. Scientists at NOAA's Pacific Marine Environmental Laboratory (PMEL) considered many possibilities, from secret military exercises to unusual ship engine noises. The sound's profile did share characteristics with marine animal calls, which led to speculation about a colossal, undiscovered creature lurking in the ocean's depths. If a blue whale, the loudest known animal, were to make such a sound, it would have to be significantly larger than any specimen ever recorded.

The Antarctic Connection

The mystery of The Bloop persisted for years. As NOAA researchers continued their acoustic monitoring work, they deployed more hydrophones closer to Antarctica to study seafloor volcanoes and earthquakes. Between 2005 and 2010, acoustic data gathered from near the continent revealed the true source. The Bloop was not biological at all; it was the sound of a cryoseism, or "icequake".

The acoustic signature of The Bloop perfectly matched the sounds of massive icebergs cracking and breaking away from Antarctic glaciers. These ice-calving events release immense amounts of energy, generating powerful sound waves that can travel across entire ocean basins. The origin point was triangulated to a remote area of the South Pacific, west of the southern tip of South America. The specific icebergs that generated the 1997 sound were likely located between the Bransfield Strait and the Ross Sea. Today, NOAA's acoustic arrays detect tens of thousands of similar icequakes annually, a frequency that is increasing with the planet's warming climate.

The 1997 Sound Louder Than a Blue Whale

A Sound from the Deep

The Antarctic Connection

💡Fun Facts

References

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Practical Information

The 1997 Sound Louder Than a Blue Whale

A Sound from the Deep

The Antarctic Connection

💡Fun Facts

References

There's more in the app

Practical Information

Nearby curiosities

Nearby curiosities