CORVALLIS, Ore. – The ebb and flow of the ocean tides, generally
thought to be one of the most predictable forces on Earth, are
actually quite variable over long time periods, in ways that
have not been adequately accounted for in most evaluations of
prehistoric sea level changes. Due to phenomena such as ice
ages, plate tectonics, land uplift, erosion and sedimentation,
tides have changed dramatically over thousands of years and may
change again in the future, a new study concludes. Some tides on
the East Coast of the United States, for instance, may at times
in the past have been enormously higher than they are today – a
difference between low and high tide of 10-20 feet, instead of
the current 3-6 foot range. And tides in the Bay of Fundy, which
today are among the most extreme in the world and have a range
up to 55 feet, didn’t amount to much at all about 5,000 years
ago. But around that same time, tides on the southern U.S.
Atlantic coast, from North Carolina to Florida, were about 75
percent higher. The