Will Global Warming Unleash More Seismic Activity?

At first glance, there doesn't seem like there could beGlacial melting has a less direct but just as unsettling
any connection between global warming and seismicadditional impact on global seismic activity. The
activity. After all, why would the earth become lessreliquified water released raises sea levels and
stable just because it's a little warmer?increases the weight on the ocean floor, unbalancing
Well, connected they are. The earth's crust is a lottectonic forces deep below the surface. Underwater
more sensitive than you might think. There are wellquakes and therefore tsunamis could thus become
documented cases of even the load of water in amore frequent. Though they get little attention, glacial
new dam triggering earthquakes in the local area.melting of the Antarctic ice is already causing
A number of geologists say glacial melting, in particular,earthquakes and underwater landslides.
will unleash pent-up pressures in the Earth's crust,Other hotspots at high risk of submarine earthslides -
causing extreme geological events such assimilar to the one that set off the disastrous tsunami in
earthquakes, tsunamis and volcanic eruptions.Indonesia in 2004 - include seaward of the mouths of
Consider this: a cubic meter of ice weighs nearly a tonthe Ganges, Nile and Amazon rivers, as well as much
and some glaciers are kilometers thick. This prodigiousof the Atlantic and US coast (E. G. Nisbet, 2004.)
weight acts to suppress tectonic movements in theEven the shape of the Earth appears to have been
underlying crust, and plug cracks where volcanicsignificantly influenced by climate events due to
magma might otherwise escape to the surface. Whenchanges in the mass of water stored in oceans,
the weight is removed through melting, the suppressedcontinents and atmosphere. Satellite data indicate the
strains and stresses of the underlying rock are free tobulge in Earth's gravity field at the equator is growing,
come to life.counteracting the long-term shrinking up to 1998 due to
As reported only this year, Harvard seismologistpost-glacial rebound.
Göran Ekström has found a striking increaseCurrent estimates of polar ice melting are too small to
in the frequency of glacial quakes, particularly inexplain the recent changes in the gravity field.
Greenland, but also in Alaska and Antarctica.Scientists postulate that global warming-induced
Greenland quakes have risen from 6 to 15 a yearredistribution of existing water mass is possibly behind
between 1993 and 2002, to 30 in 2003, 23 in 2004 andthe phenomenon. However, the specific cause still
32 in the first 10 months of 2005, closely matching theremains a mystery.
rise in Greenland's temperatures over the same period.Dramatic climate shifts of the past have also been
Their source was traced to surges and slips within iceassociated with spectacular seismic activity. During the
sheets, where rapid melting is causing water to collectlate glacial and early Holocene periods when climate
under glaciers, making them glide faster into the sea,was see-sawing from one extreme to another in the
triggering quakes.interval known as the Younger Dryas, submarine
Similarly, retreating glaciers in southern Alaska are likelylandslips were widespread. For example, 8,200 years
to open the way for future earthquake activity.ago an enormous slip in the Norwegian Sea involving
Accelerated melting of glacial ice decreases the loadover 3000 cubic kilometers of material set off a
on the Earth's crust, thereby decreasing the pressuremassive tsunami more than 20 meters high. At about
holding volcanic conduits closed. Already, we arethe same time mega-earthquakes ruptured the crust
seeing evidence of new volcanic activity in Antarctica.and lifted Scandinavia's mountain backbone by 5 to 15
A new, previously unknown volcano has appeared onmeters. Could it happen again?
the sea bottom in waters off the Antarctic Peninsula, inThe science suggests that as redistribution of the
an area with no previous record of volcanic activity.Earth's mass induced by global warming disturbs the
Investigations into a large area of surface slumping onrelative equilibrium of its crust, monumental forces in
the West Antarctic Ice Sheet revealed a hugethe form of increasing earthquakes, tsunamis and
accumulation of water underneath that has now beenvolcanic activity could be unleashed. And the forecasts
shown to be due to an active volcano erupting underfrom some quarters are dramatic - - not only will the
the sheet.earth shake, it will spit fire (Bueckert, 2006).