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"Brrrrrr!
Where the heck did all that snow come
from? I thought this was the tropics!"
"Man!
Is that a glacier over there? How's a self-respecting dinosaur supposed
to get a square meal? The snow and ice are so thick that even Steggie's
Gourmet Burger Heaven is buried! I don't think I can make it without
my daily Quarter Tonner Veggie Burger! (Dinosaurs eat a lot, you
know!)" "This is too cold for me! How did this happen?
There's not an asteroid or volcano in sight!"
Actually,
in this alternative explanation of the
demise of the dinosaurs, the climate change
that destroyed their food supplies came
not from major sudden disasters, but from
slow changes in the orbit of the Earth
itself. This explanation is a little complicated,
so pay close attention.
The story
begins about 150 years ago when scientists learned to recognize
the piles of rock and the marks on rocks left by small glaciers
in the Alps. They then found tell-tale evidence of giant glaciers
scattered over much of North America and Europe. These giant glaciers
or ice sheets were nearly a mile thick and extended across millions
of square miles of land that today are covered with grass and forest.
Careful study showed that the ice sheets had grown and shrunk across
the continents not once, but many times. The glaciers appeared and
disappeared during repeated cycles of hot and cold weather, each
cycle lasting about 100,000 years.
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