for National Geographic News
They may not sound like Bing Crosby, but some icebergs can sing, scientists report.
"They are partly melodic, but not really melodic like singing, more like the screeching of a horror film in parts," said Vera Schlindwein, a scientist with the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany.
"Some are like an orchestra when all the violins start [playing] at once. Then, all of a sudden, it develops into harmonic sounds like a humming bird," she added. "It is a well-developed sound."
The sounds are too low to be heard by humans and are only audible when played at higher speeds, Schlindwein said.
She and her colleagues picked up the acoustic noise from seismic recordings made along Antarctica's South Atlantic coast in 2000.
The researchers believed the tremors were from volcanic activity. But when they tracked to their source, the scientists discovered the rumblings' true origin.
The team published their study last week in the journal Science.
Schlindwein notes that some types of volcanic tremors, when viewed on a seismograph, are "absolutely undistinguishable from these iceberg tremors."
Since icebergs are easier to study than rocky volcanoes, Schlindwein said examining the mechanisms that make the icebergs screech may help scientists better understand the mechanisms of volcanic tremors, which often precede an eruption.
Richard Aster, a geophysicist at the New Mexico Institute of Mining and Technology in Socorro, has measured similar iceberg tremors in the Ross Sea along Antarctica's Pacific Ocean coast.
He says that, generally speaking, iceberg tremors and volcanic tremors have similar characteristics. But he cautioned that "we're still at the early stage of trying to understand these sorts of signals."
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