Geology Reference
In-Depth Information
Figure 6: Diversity and extinction over the ast 500 million years.
( redrawn from Richard B. Primack, Primer of Conservation Biology, Sinauer Associates Incor-
porated, 2004 )
The last mass extinction happened about 65 million years ago, when a meteorite some
10km across struck the Earth in the Yucatan region on Mexico's Caribbean coast, fol-
lowed by a huge flood basalt event in India. Opinion within the scientific community is
divided over what caused the other four mass extinctions. Most experts favour meteorite
impacts or changes in sea level and temperature wrought by the massive forces of plate
tectonics; others believe that too much internal interconnection and complexity with-
in ecosystems triggered these massive global losses of biodiversity. Notice, however, a
striking fact: after each mass extinction it took 5-10 million years before the planet once
again teemed with diverse life. This ability to recover from mass extinctions is strong
evidence for Gaia.
Modelling Gaia: Daisyworld and Beyond
 
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