Scientists have recorded ice quakes in the Greenland Ice Sheet by installing a fibre optic cable in a special borehole. The tunnel leading to the borehole is shown above. (Photo: Andreas Fichtner/ETH Zurich)
For the first time, researchers have recorded multiple “icequakes” that periodically affect the Greenland ice sheet. These phenomena may explain the intermittent movement of the island’s frozen rivers down to the sea, scientists say.
Scientists detected the quakes by sinking a fiber-optic cable into a 1.7-mile (2.7-kilometer) deep hole in the Northeast Greenland Ice Stream, Greenland's largest frozen river and the main artery carrying ice from the ice sheet's interior to the North Atlantic Ocean.
Like earthquakes, icequakes are seismic events that occur when ice cracks and two pieces of ice rub against each other.
Ice quakes in Greenland have gone undetected until now because a layer of volcanic particles buried 2,950 feet (900 meters) beneath the ice prevented them from reaching the surface, researchers said in a report. The particles were formed by a massive eruption of Mount Mazama, in what is now Oregon, about 7,700 years ago, they said.
Volcanic particles not only prevent seismic waves from traveling to the surface, but can also directly trigger earthquakes, Andreas Fichtner, a professor of geophysics at the Swiss Federal Institute of Technology (ETH) in Zurich and lead author of a new study published Feb. 6 in the journal Science, said in a statement. Ice earthquakes are likely caused by impurities in the ice, such as sulfates and other particles, that can destabilize the ice and cause small cracks to form.
“We were struck by this previously unknown connection between ice flow dynamics and volcanic eruptions,” Fichtner said.
Scientists set up camp on the Northeast Greenland Ice Creek, which is the largest frozen river on the island.
Ice quakes can trigger other ice quakes in a domino effect, thereby spreading horizontally over significant distances, according to the statement.
Sourse: www.livescience.com
