- Location
- South Pacific; Antarctic source region
- Water
- Pacific and Southern oceans
- Period
- 1997 recording; later acoustic comparisons
- Case status
- Explained
- Last reviewed
- November 5, 2026
Explained acoustic phenomenon. The exact source iceberg is not identified in the cited account; no unknown animal is required by the evidence.
What the instruments heard
In 1997, hydrophones in the southern Pacific recorded an unusually powerful underwater sound. The signal became known as the Bloop. NOAA’s National Ocean Service account explains that researchers were listening for underwater volcanic activity when the recordings drew their attention.
An unfamiliar sound is an observation, not an identification. Its initial strangeness did not establish an animal source, and the later explanation should travel with any retelling of the mystery.
Following the comparison
The Pacific Marine Environmental Laboratory’s acoustic account describes the recordings as consistent with icequakes produced by large icebergs cracking and breaking. Similar signals recorded near Antarctica supplied a physical comparison.
The laboratory also labels its posted Bloop recording as sixteen times faster than the recorded signal. Playback speed changes how a sound is perceived; a circulating clip should not be mistaken for the event heard at its original rate.
What remains uncertain
The cited laboratory page discusses a likely Antarctic source region without naming one proven source iceberg. Uncertainty about that precise location does not make the icequake explanation an unexplained biological event. The interest lies in how measurement changed the account.
Documented timeline
Open an event to read its account and supporting source. Dates may be approximate.
Summer 1997 A powerful signal is recorded Documented
Hydrophones detected the broad-spectrum sound later called the Bloop.
Subsequent Antarctic monitoring A physical explanation emerges Reported
Comparable sounds were associated with ice fracturing.
Early 2008 Further icequake tracking Documented
PMEL describes using icequake signals to track disintegrating iceberg A53a; this is a comparison, not identification of the 1997 source.
Sources & records
-
What is the bloop?
Institutional explanation of the original recordings and their subsequent interpretation. This entry does not treat speculative animal explanations as evidence.
-
Icequakes (Bloop)
Research-program account with spectrograms and audio links. The page labels the Bloop audio as sped up sixteen times; its proposed source region is approximate.