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is established that mimics both the 11-year sunspot cycle and the 22-year solar
cycle or possibly the early lunar cycle, which today is about 19 years.
Rocks containing carbonate minerals lie just above the glacial deposits.
This indicates a hothouse effect produced by a profusion of volcanic activity
that pumped carbon dioxide into the atmosphere, heating Earth and melting
the great glaciers. Not long after the ice disappeared near the end of the Pro-
terozoic, a great diversity of animal life culminated with the evolution of
entirely new species, the likes of which have never existed before or since.This
forever changed the composition of Earth’s biology. Life-forms took off in all
directions, producing many unique and bizarre animals. The rapid evolution
produced three times as many phyla, groups of organisms sharing the same
general body plan, as are living today.
Many unusual creatures occupied the ocean. The highest percentage of
experimental organisms, animals that evolved special characteristics, came into
being than during any other interval of Earth history. As many as 100 phyla
existed, whereas only about a third that number are living today.This biolog-
ical exuberance set the stage for more advanced species.Also, for the first time,
fossilized remains of animals became abundant due to the evolution of lime-
secreting organisms that constructed hard shells.60
Historical Geology
EUROPE
and
ASIAAFRICAANTARCTICAINDIA AUSTRALIASOUTH
AMERICANORTH
AMERICAFigure 39The location
of Precambrian glacial
deposits.