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Copyright 1997 The Buffalo News
The Buffalo News
August 10, 1997, Sunday, FINAL EDITION
SECTION: VIEWPOINTS, Pg. 6H
LENGTH: 513 words
HEADLINE: HAVE EXPERTS SOLVED ONE OF SCIENCE'S TOP MYSTERIES?
BYLINE: JEFFREY CHUANG; Dallas Morning News
DATELINE: DALLAS
BODY:
A titanic rotation of the Earth's surface 535 million years ago may have triggered the greatest explosion of life this planet has ever seen, scientists have reported.
In last week's issue of the journal "Science," researchers from the California Institute of Technology and the University of Puerto Rico report evidence that during a 15 million-year period, the Earth's surface and mantle rotated one-quarter of the way around the globe. During the same period, 10 times more kinds of creatures appeared on Earth than had lived there before, fossil evidence shows.
The scientists believe that the massive relocation of land and oceans caused vast climate changes. These changes may have sparked a mysterious diversification of life known as the "Cambrian explosion," in which virtually all animal lineages suddenly arose, the researchers said.
"The thing that makes this peculiarly interesting is its association with the Cambrian explosion," said Joseph Kirschvink, a professor of geobiology from Caltech and head of the research team.
If the researchers' hypothesis is correct, they will have solved one of biology's most perplexing puzzles. Why life suddenly diversified 530 million years ago has confounded scientists since the dawn of the theory of evolution.
In examining fossils, "Charles Darwin recognized 150 years ago that something was strange," Kirschvink said.
"It's logical," said Blair Hedges, an evolutionary biologist at Pennsylvania State University. "Geology has a big effect on evolutionary history throughout the fossil record."
In their study, Kirschvink, graduate student David Evans and geochemist Robert Ripperdan analyzed rocks from Australia and North America that formed between 500 million and 600 million years ago.
As a molten rock cools, little magnetic particles in the rock line up, creating a kind of "magnetic arrow" inside. The rock's arrow points toward the magnetic north pole just as a compass needle does.
By using the rocks' magnetic arrows to pinpoint the rocks' original locations, scientists reconstructed several maps of the ancient globe.
In the maps just before the Cambrian explosion, much of Earth's land mass was concentrated near the poles. But the spinning of the planet pushed land away from the poles and toward the equator, the scientists said. By the time the Cambrian explosion began, Earth's land masses had begun to move very rapidly, the researchers said.
Essentially, the skin of Earth slipped, the scientists said. The planet's outer layer rotated 90 degrees, swinging the former north and south poles to the equator.
While this kind of toppling of the surface has never been noted on Earth before, the scientists said there is evidence that both Mars and the moon have reoriented themselves this way.
This rotation of Earth's surface would have pushed frigid polar regions to the tropics, said the researchers. Torrid tropical regions, meanwhile, would have iced over. Within the turbulent 15 million-year period, a region's climate could have changed dramatically many times.
LANGUAGE: ENGLISH
LOAD-DATE: August 12, 1997