Did a shift of the earth cause the Cambrian explosion?

What's better on the Fourth of July than to post about an explosion --
the Cambrian explosion -- and fireworks in the history of life.

I must admit that I was suprised to find out about the 90 degree shift
in the earth's axis relative to the continents as described here:

"One of the greatest of all biological mysteries is why the diversity of
living things suddenly exploded at this time. One hypothesis links a
series of massive oscillations in climate with the period of maximum
diversication that occurred during the interval between about 540
million and 520 million years ago. By analyzing the magnetic
orientation of Cambrian rocks. Joseph Kirschvink and his colleagues
have shown that during this short interval there was a 90-degree shift
in the orientation of the poles of the earth relative to the continental
landmasses. The massive polar shift resulted in global oscillations in
climate, which provided new niches for evolving species. The marine
sediments from this interval reveal a series of 10 enormous oscillations
in the amount of carbon 13, an indication of the aggregate amount of
plant and animal life. These huge Cambrian oscillations exceeded the
magnitude of the mass extinction even at the end of the Cretaceous
period 65 million years ago, which resulted in the destruction of 75
percent of the animal species then living and led to the emergence of
mammals in the following period. During the Cambrian explosion, 10
rapid proliferations of life were followed in each case by a rapid
reduction as habitats were created and destroyed. The fossil record
shows that new types of animals appeared during these phases, and so
these massive oscillations may have driven the rapid evolutionary
diversification that occurred during the Cambrian."

--John Allman, _Evolving Brains_, p. 67


It's important to distinguish three different types of shifts in the
earth's poles:

1. Flips in the earth's magnetic poles, which have occurred hundreds of
times in earth's history.

2. Shifts where the earth's axis of rotation maintains its orientation
relative to its orbit around the sun, but the earth's surface reaches a
new orientation relative to its axis. This is the type of shift
described above.

3. Actual shifts in the earth's axis of rotation. This probably hasn't
happened to any great extent since the earth had a glancing collision
with a passing body early in its history and the moon was spun off.

Here's another reference to the same topic:

"When Earth tumbled - researchers find evidence of sudden shift in
continents 500 million years ago - Brief Article"

http://findarticles.com/p/articles/mi_m1511/is_n11_v18/ai_19847175


--dkomo@xxxxxxxx




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Relevant Pages

  • Did a shift of the earth cause the Cambrian explosion?
    ... What's better on the Fourth of July than to post about an explosion -- the Cambrian explosion -- and fireworks in the history of life. ... One hypothesis links a series of massive oscillations in climate with the period of maximum diversication that occurred during the interval between about 540 million and 520 million years ago. ... Joseph Kirschvink and his colleagues have shown that during this short interval there was a 90-degree shift in the orientation of the poles of the earth relative to the continental landmasses. ... The marine sediments from this interval reveal a series of 10 enormous oscillations in the amount of carbon 13, an indication of the aggregate amount of plant and animal life. ...
    (talk.origins)
  • Re: Did a shift of the earth cause the Cambrian explosion?
    ... the Cambrian explosion -- and fireworks in the history of life. ... I must admit that I was suprised to find out about the 90 degree shift ... a series of massive oscillations in climate with the period of maximum ... mantle is such that the equatorial bulge ...
    (talk.origins)
  • Re: Did a shift of the earth cause the Cambrian explosion?
    ... the Cambrian explosion -- and fireworks in the history of life. ... I must admit that I was suprised to find out about the 90 degree shift ... series of massive oscillations in climate with the period of maximum ...
    (talk.origins)
  • Re: Did a shift of the earth cause the Cambrian explosion?
    ... the Cambrian explosion -- and fireworks in the history of life. ... I must admit that I was suprised to find out about the 90 degree shift ... series of massive oscillations in climate with the period of maximum ... Shifts where the earth's axis of rotation maintains its orientation ...
    (talk.origins)
  • Re: Did a shift of the earth cause the Cambrian explosion?
    ... the Cambrian explosion -- and fireworks in the history of life. ... I must admit that I was suprised to find out about the 90 degree shift ... the bulge in the mantle doesn't move. ... get scraped onto the edge of the overriding plate. ...
    (talk.origins)