The ocean covers 71% of our planet.
Yet over 95% of it remains unexplored.
–There's a whole world of sound underwater
that we are not normally aware of.
–In 1997, our ignorance of these
mysterious ocean depths was made evident
when a strange sound was recorded deep within the ocean—
puzzling scientists and igniting the public's imagination.
This underwater acoustic wonder became known as “the bloop.”
In 1997, scientists from NOAA,
the National Oceanic and Atmospheric Administration,
were running underwater acoustic research
off the southern coast of Chile.
–At the time, we had a number
of these hydrophone moorings deployed just off
South America, looking for volcanic activity
on a long mountain chain on the seafloor.
–The scientists were using hydrophones,
which are just like regular microphones that are adapted
to surviving the really high pressures underwater.
And the data gets analyzed to look at what sounds happened
over the past months or years that they recorded.
–While logging the data from the hydrophones,
scientists noticed an unexpected acoustic pattern.
It was one of the loudest noises ever recorded
in the earth's oceans—
a distinct sound that reminded scientists
of a cartoonish bloop.
–It was kind of short like an earthquake,
but it wasn't in the right frequency range.
It was higher than normal signals.
Moments like those for a scientist are a combination
of skepticism and also excitement.
–The bloop was so remarkable,
the same sound was recorded
on another hydrophone over 3,000 kilometers away.
–Sound speed underwater is a function of three things.
First, the temperature.
So if you have warm water, sound travels faster
because the molecules have more energy,
and they can vibrate and transmit the pressure wave faster.
Salty water also travels sound faster.
And then the high pressure, of course,
so in the deep sea, you have a faster sound speed.
In that deep sound channel, sound likes to get trapped
because of the pressure and the temperature.
You can think of this as being a path of least resistance
or a tunnel that the sound gets trapped in
and travels really far.
–So what could have produced
this unprecedented phenomenon?
–In general, the soundscape is composed of
the biological, so animal vocalizations;
the natural or geophysical sounds,
so anything that comes from the ground or from the surface;
and then the anthropogenic sounds,
which are the man-made noises.
–Some speculated that the military
was conducting tests in the area.
But a call to the Navy quickly put an end to that theory.
So scientists turned their attention
to the biological world for answers.
–Generally, low-frequency sounds are associated
with really big sources.
So if you think in the animal world,
the animal with the lowest-frequency sounds are going to be
the really big whales—the blue whale or the fin whale.
–The blue whale is the largest species
ever known to have lived on Earth.
They can grow to 105 feet long and weigh 200 tons.
This incredible ocean creature is capable
of projecting sounds 1,000 miles away.
But the bloop echoed over 3 times farther than that distance.
–What this tells you is that whatever the origin was,
it was something big.
It was a big phenomenon that caused it.
–In 2002, NOAA researcher Dr. Christopher Fox
suggested the origin of the mysterious bloop
could be biological.
When the public heard this news,
coupled with the recording of the bloop,
speculation and conspiracy theories were rampant.
–People got excited about it possibly being a new species
that we didn't know about, or some sea monster.
–Fans of H.P. Lovecraft were especially excited.
His books described a fictional sea monster
that lived near where the bloop originated.
Readers speculated that the sound was caused
by some unidentified sea creature.
–So while the imagination of the public is running wild,
in the lab, the scientists are doing the hard work.
And they are looking for explanations for the sound.
But it would be almost 10 years before a team
of scientists finally got a break
in the case of the bloop.
–We started doing hydrophone research
off the Antarctic Peninsula.
We put a hydrophone array down around King George Island.
We get the data back and see that the sound
of ice breaking, ice cracking is really, really a dominant source
of sound in that southern ocean.
–NOAA researchers discovered
striking similarities between the puzzling bloop
and this frequent oceanic event.
–Scientists concluded that the bloop was originated
by one of these ice quake movements.
So as the temperatures warm up,
movement happens within the glacier.
It's the same principle as the plates
moving on the bottom of the sea.
These ice pieces are moving, and they're scratching
and crashing into each other and creating noise.
–To the disappointment of many,
the scientific community put theories
of monstrous sea creatures and the mystery
of the bloop to rest.