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Water running through the intricate inner channels of icebergs can create erratic and high-pitched sounds reminiscent of an orchestra warming up.
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Singing icebergs
The chilling songs of icebergs may help scientists better understand
volcanic eruptions, earthquakes and plate tectonics
By Chris Mason
They say swans sing before they die, but is it possible large, lumbering icebergs also
screech a final tune?
German scientists have recently discovered that water running through the interior
channels of Antarctica’s icebergs creates a shrill tune when they run aground that they
found puzzling at first but now find fascinating. They published their findings in November
2005, telling the story of how they stumbled onto their discovery back in 2000.
"At first we had no explanation," says Christian Müller, a scientist
with Fielax, a German company that teamed up with the Alfred Wegener Institute for Polar
and Marine Research to study the phenomenon. "We thought it was technical problems
with the sensors or data acquisition," he adds.
Their tunes ranged from that of a humming beehive to the
chaotic, shrill pulse of violins warming up for a performance. |
But the sounds were not the result of a technical glitch. Although inaudible to the
human ear, the noises were measurable when played at higher speeds. Their tunes ranged
from that of a humming beehive to the chaotic, shrill pulse of violins warming up for
a performance.
The sounds are thought to come from water flowing within the iceberg’s network of crevasses
and tunnels. The flow reaches a high enough pressure to produce sound when the iceberg
grounds and water that normally helps push the iceberg begins to rush through it instead.
That water current causes elastic vibrations similar to what occurs inside an organ pipe,
according to scientists.
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The source of the harmonic currents covered an area 30 kilometres by 50 kilometres — an
area twice the size of Toronto. |
At first experts remarked that the sounds were eerily similar to those recorded during
volcanic tremors.
"From a geological viewpoint, this was not impossible since the localization was
in an old crustal rift system," says Müller from a research station in the
Antarctic where he is prepared to record any iceberg harmonies within range. After further
analysis they recognized the source of the sound was moving, cancelling out the possibility
of the sound originating from the earth’s crust.
They found that not only was it moving, but the source of the harmonic currents covered
an area 30 kilometres by 50 kilometres — an area twice the size of Toronto. The
iceberg they stumbled upon was called B-09A and it quickly became clear that the team
of researchers was onto something new.
Their most significant recording came on July 22, 2000 when researchers were treated
to a 16-hour show. The sounds were triggered when a collision between the iceberg and
the continental slope caused two brief earthquakes. Researchers heard a two-hour sequence
of screeches, and then a one-hour intermission. But the iceberg was just warming up for
a 13-hour grand finale harmonic tremor. Those tremors were detected 800 kilometres away
with strengths comparable to volcanic tremors measured at Mount St. Helens.
The tremors were detected 800 kilometres away with strengths
comparable to volcanic tremors measured at Mount St. Helens. |
Researchers continue to explore the phenomenon and how it can be useful in other fields.
It seemed natural to apply the knowledge to volcanic tremors since it was initially thought
to be the source of the music.
"The iceberg tremor recordings are strikingly similar to volcanic tremors," Müller
says. Despite the fact that icebergs have much simpler structures than volcanoes, they
are physically easier to work with. The similarities between volcanic and iceberg tremors
include long durations and amplitudes, as well as common shifts in frequencies.
Müller and other scientists hope to exploit these similarities to help experts
develop a better method for predicting volcano eruptions. Volcanic tremors often signal
a looming eruption, so establishing a method for understanding and examining the tremors
may very well allow experts to predict the eruptions more accurately and, most importantly,
allow for earlier warnings to evacuate.
The research is still in its early stages, but Müller and his colleagues hope
their continued work will not only lead to a more concrete understanding of icebergs,
but also to a better feel for their red-hot polar opposites.
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