Thursday, February 11, 2016

North Atlantic Land Bridge

Looking northwest across the tops of Ireland and Scotland, toward Greenland.
Hat-tip to the ever watchful Lucas Macias.

Land Bridges

Animated GIF of the Bering Land Bridge.

Most of us are familiar with the Bering Land Bridge.  That is the shallow straight that was, presumably, exposed as dry land during periods when larger amounts of water were locked up in glaciers.  It is the path that Homo sapiens and numerous other animals followed when they came to North America.

Another view of the potential land bridge east of Greenland.  You can see how this made tracking Russian subs much easier.  Getting out of their north Atlantic bases left them as exposed as a rhino trying to sneak across a putting green.

Unbeknownst to me, there is evidence that there was a North Atlantic Land Bridge as recently as 5.5 million years ago.  That is a blink-of-an-eye in geological time.  For reference, that is about the age that "Lucy", the oldest hominid fossil, has been dated as.

The basic evidence

The "oak" of Robin Hood and Sherwood Forest.  It is genetically very similar to the cluster of White Oak species in Eastern North America
There are some very similar species that have "discontinuous ranges."

The range of Quercus alba, the White Oak
Pollen of oak types that are now restricted to North America were found in glacial ice in Iceland.  That ice was dated to 5.5 million years of age.

So, how much lower would the ocean have to be?

Eastern North America and Western Europe with ocean level 500 meters lower than current level.  Image from HERE.  At this level there are four narrow straights that separate North America from Europe.
Same window but with oceans 1000 meters lower.  At this level animals could walk across the resulting land bridge.
Changes in ocean levels are nothing new. If we go back in time the changes that have the climate worriers in a sweat are relatively small potatoes.  And we don't have to go back to the age of dinosaurs, either.  These levels occurred when human-like apes were wandering what is now Kenya.

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