Friday, February 11, 2005

More environmental impact of the tsunami

First, it was a 9.3, not a 9.0. From Live Science (Feb 8):
A new analysis of the December earthquake that caused disastrous tsunami waves to strike Asia and Africa finds it was three times more powerful than earlier measurements suggested. This would make it the second largest earthquake ever instrumentally recorded.
Ok, on to the environmental impact (see also this earlier post). From Reuters (Feb 10; via Yahoo news), "Asia Quake, Tsunami Moved Islands, Shortened Days" by Jim Loney (highlights):
Six weeks after the tsunami that may have killed 300,000 people on the shores of the Indian Ocean, scientists are discovering more about the changes wrought by the magnitude 9 quake, the fourth-largest in the last century.

It caused upheaval on the sea floor near its epicenter off the northwest coast of Indonesia's Sumatra island and moved several other islands, but scientists say any movement of land mass can be measured in inches rather than tens of yards.
On the other hand...
Scientists at NASA, the U.S. space agency, said the Dec. 26 quake -- the largest to rattle Earth since 1964 in Alaska -- disrupted the planet's rotation and shaved 2.68 microseconds, or millionths of a second, from the length of a day.

NASA scientists B. F. Chao and Richard Gross calculated it shifted Earth's mean north pole about 1 inch and made the planet slightly less oblate, or flattened at the poles.

"Physically, this is analogous to a spinning skater drawing arms closer to the body, resulting in a faster spin," they wrote in an article in Eos, a publication of the American Geophysical Union.

But they said these changes are based on calculations rather than measurements. The changes are so small they are either difficult to measure or too small to detect.

Many earthquakes shake the planet's axis and affect its rotation, scientists added, but their impact is too small to measure.
Other sorts of impact to reefs, mangroves, and coastal land:
Some coral reefs--undersea gardens that act as shelter and nursery to a wide range of marine species--were crushed by the waves. Corals grow slowly, some only an inch or two a year, so their recovery could take decades.

John Pernetta, a UNEP official in Bangkok, said the extent of damage to some of the coral reefs around Thailand was very high -- up to 80 percent in some places. Their recovery was uncertain.

Mangroves torn out by the waves will fare better, he said, as they leave behind roots and seeds that will help them regenerate.

"Long-term damage to mangroves by hurricanes or tsunamis doesn't really happen," Pernetta said. "After five to 10 years you don't even know anything has happened."

Vast stretches of Sumatra's west coast were turned brown by the tsunami as rice paddies and other vegetation were swamped by salt water. It could take two or three rainy seasons to wash the salt from the saturated land, experts say.

The tsunami waves ate away beaches and coastal areas in Thailand, Indonesia and Sri Lanka, radically changing maps.

The waves also carried sediment ashore, said Phil Liu, a Cornell University wave researcher who led a scientific team to Sri Lanka in mid-January.

"There is evidence that a lot of sediment was being brought onshore," he said. "A post office on the east coast was found with sediment deposits on the roof."

But it remains to be seen whether such sediment is good for the land or a bane because of its high salt content.

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