for National Geographic News
About 80 million years ago—a time when dinosaurs ruled the Earth—global sea levels were roughly 560 feet (170 meters) higher than they are today, according to a new study.
If sea levels were that high now, vast regions would be flooded: most of northern Europe, large sections of South America, the East Coast of North America, and parts of Australia.
In Washington, D.C., the tip of the Washington Monument would poke just above the water. The base of the 555-foot-tall (169-meter-tall) obelisk is currently 30 feet (9 meters) above sea level.
(Related news: "Global Warming Is Rapidly Raising Sea Levels, Studies Warn" [March 23, 2006].)
The finding stems from more than a decade of effort to virtually reconstruct ancient ocean basins to understand how their size and depth have changed since the Cretaceous, which lasted from 145.5 to 65.5 million years ago.
The result is a dramatic image of historic sea level change that goes beyond what is expected in the coming decades due to rapid global warming-induced ice cap melting.
"There're natural processes that also contribute to sea level change and are in fact independent of ice cap melting," said Dietmar Müller, a geologist at the University of Sydney in Australia.
In fact, the data reveal that the long-term trend in sea levels since the Cretaceous has been downward, said Müller, who led the study appearing in tomorrow's issue of the journal Science.
When this trend is extrapolated out 80 million years from now, it suggests that even if all of today's ice caps were to melt, sea levels would be 230 feet (70 meters) lower than they are today.
Rising and Sinking
Pictured on today's globe, that much of a sea level drop would mean that Indonesia would be largely connected to mainland Southeast Asia.
Furthermore, all the continents would be larger, so today's coastal cities would be stranded inland.
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