2006/07/04
OTTAWA - So the warnings of harsher heat waves, stronger hurricanes and rising seas fail to impress. How about volcanic eruptions in the Arctic, or a tsunami off the coast of Newfoundland? The latest scientific discipline to enter the fray over global warming is geology. And the forecasts from some quarters are dramatic - not only will the earth shake, it will spit fire. A number of geologists say glacial melting due to climate change will unleash pent-up pressures in the Earth's crust, causing extreme geological events such as earthquakes, tsunamis and volcanic eruptions. A cubic metre of ice weighs nearly a tonne and some glaciers are more than a kilometre thick. When the weight is removed through melting, the suppressed strains and stresses of the underlying rock come to life. University of Alberta geologist Patrick Wu compares the effect to that of a thumb pressed on a soccer ball - when the pressure of the thumb is removed, the ball springs back to its original shape. Because the Earth is so viscous, the rebound happens slowly, and the quakes that occasionally shake Eastern Canada are attributed to ongoing rebound from the last ice age more than 10,000 years ago. Melting of the ice that covers Antarctica or Greenland would have a similar impact, but the process would be accelerated due to the human-induced greenhouse effect. "What happens is the weight of this thick ice puts a lot of stress on the Earth," says Mr. Wu. "The weight sort of suppresses the earthquakes but when you melt the ice, the earthquakes get triggered." When a quake happens under water, it can cause a tsunami. Mr. Wu said melting of the Antarctic ice is already causing earthquakes and underground landslides although they get little attention. He predicted climate warming will bring "lots of earthquakes." When the glaciers melt, the reliquified water causes sea levels to rise and increases the weight on the ocean floor, which could also have an effect on the grinding tectonic plates deep below the surface. The Earth's crust is more sensitive than some might think. There are well-documented cases of dams causing earthquakes when the weight of the water behind a dam fills a reservoir. Alan Glazner, a volcano specialist at the University of North Carolina, said he was initially incredulous when he found a link between climate and volcanic activity off the coast of California. "But then I went to the library and did some research and found that in many places around the world especially around the Mediterranean they see similar sorts of correlations." "When you melt glacial ice, several hundred metres to a kilometre thick "... you've decreased the load on the crust and so you've decreased the pressure holding the volcanic conduits closed. "They're cracks, that's how magmas gets to the surface "... and where they hit the surface, that's where you get a volcano." No one has claimed the Christmas tsunami of 2004 was triggered by rising sea levels. But that event seems to have sparked new interest in the links between climate and geology. "All over the world, evidence is stacking up that changes in global climate can and do affect the frequencies of earthquakes, volcanic eruptions and catastrophic sea-floor landslides," says British geologist Bill McGuire, writing in New Scientist magazine. "Not only has this happened several times throughout Earth's history, (but) the evidence suggests it is happening again," says Mr. McGuire, professor of geological hazards at University College in London. Mr. Glazner said the main impact of glacial melting is due to reduced weight on the places losing glaciers rather than the increased weight on the ocean floor. "If you melt that glacier and the water runs into the oceans, that water is spread over the entire surface of the ocean and it might add a millimetre to the thickness of the oceans or something, but you've taken a kilometre off of that place where the glacier used to be
The South Coast disaster: Newfoundland's tsunami1929. Nov.18 It happened Nov. 18, 1929, long before the Dominion of Newfoundland joined Canada; it wasn't on the scale of this week's catastrophe, but what happened 76 years ago was a tragedy by any measure. It took 29 lives, most of them in Newfoundland. An earthquake rumbled in the Grand Banks. It was so powerful, it was felt in Montreal and New York. Less than three hours after the quake, a fast-moving giant wave washed over the Burin Peninsula. People there have never forgotten. Vince Hanrahan in St. John's is horrified by what he's seen of the tsunami in the Indian Ocean. He can't believe so many people are dead. "When I see this, how many people? How many now, over 60,000? Hard to believe, isn't it?" he says. Hanrahan has a good idea of what's happening there. "It's the same over there. Maybe the husband is gone, the mother is gone, the kids are left. Who looks after them?" he says. Hanrahan survived the most devastating tsunami in Canada. It happened on Newfoundland's Burin Peninsula 76 years ago. The first sign of trouble began with a ground shaking. "You notice with the water coming and going, you know, and then the shaking of the land and so on, and then when I went up to the house and my mother's dishes were falling off the shelf and, of course, they were smashed. My mother didn't know what it was," Hanrahan remembers. Doug Brushett, 90, in Bull's Cove, will never forget it. "The earth was trembling under our feet, and I was kind of frightened," Brushett says. Margaret Saint was not quite four, but she says she still remembers the tremors and the wall of water that carried her house out to sea. "They found mom and the children downstairs. Mom was found under the table and she was sewing at the time on her sewing machine. Patrick, he was found in under the couch. Rita was around there somewhere, I suppose. The baby, Bernard, was tied in the highchair," she says. Rescuers found little Margaret in an upstairs cradle. "They found me in the bed and the mattresses washed up on the side of the wall," Saint says. Author Maura Hanrahan grew up hearing so many stories about it, she wrote a book. "What happened was there was a subterranean earthquake approximately 250 miles south of Newfoundland. This caused the ocean floor to shift several yards and that unleashed a massive wave which hit the communities of the south coast at 60 miles an hour," she says. Stories about the Newfoundland tsunami abound on the Burin Peninsula, stories that are told and retold when people gather together. "I heard an awful 'roaration,' and something told me to come on out. So I came on out, and when I came out, I looked, and I only had to walk about a hundred yards, and I looked and I saw the house going out across the beach. So I knew my mother and the children was all in the house," one man said in 1974. "The lamp stayed on the table and, like, never went out. I said the Lord kept the lamp burning. Because if the lamp went out, I couldn't see the children because poor little Stanley, sometime he'd be way over there and another one would be over there. I was going all the time back and forth saving the children," a woman told a reporter. "I saw it with my own eyes, a big roll of water coming in probably 20 feet high, like right white coming, coming, coming, coming, by and by it struck the land and took the houses and stages and beaches and rocks and everything went before us. And there's only a few minutes and everything was covered and, of course, all the destruction was caused in just a few minutes," another man said. "All of a sudden, the building began to shake and shiver. So we looked at one another and finally I looked out through the window and I saw the telegraph pole shaking like anything, and I said, there must be an earthquake. So we sat there for a few minutes and then everything went blank. Our communication with the outside world went dead," another survivor said at the time. The South Coast tsunami left 29 people dead; 10,000 people were homeless. "The impact was horrendous. These numbers were small compared to what's happening now in Southeast Asia, but for the people who were affected, their lives were over," Maura Hanrahan says. "They had to start over again. They lost their homes, they lost their fishing boats, their fishing gear, their fishing sheds. They lost... A lot of them kept their money in their homes. They lost $200, $2,000, which was a lot of money at that time. They lost all their winter provisions, food." The Newfoundland government sent ships with doctors and supplies. Canada was the largest foreign donor. It donated $35,000, but above all this, individual Newfoundlanders raised more than $200,000 to help their countrymen. Remember, the year was 1929. "One of the things that I really took away from this story was the resilience of the human spirit, how people can rebuild from nothing and how generous other people are," Maura Hanrahan says. Fifty outports were devastated by the tsunami, but along with the tragedy, people remember the generosity extended to survivors, an example Vince Hanrahan hopes the world will follow for the victims in Southeast Asia