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Welcome. It looks as if everyone who's coming is already here,
so let's start, shall we? In yesterday's class, I talked about
how the Earth and the Moon are thought to have formed. As I told
you, the best theory concerning their origins seems to be the
"Single Source" theory. This states that the Earth and
Moon were made out of the same ball of molten mass. I also talked
about how the Earth eventually cooled down and how its surface
features formed. And just before the end of class, we looked at
how all the continents were fused into one gigantic continent
called Pangea. Now, to continue from where we left off, we know
for certain that this massive continent did not last forever-just
look at a present-day globe. According to current theories regarding
continental drift, this huge landmass probably began to fracture
into the continents we see today about 200 million years ago.
This date is supported by the ages of basalt flows that have been
found in the middle of the Atlantic Ocean. It is likely, by the
way, that the Atlantic did not form immediately after Pangea's
breakup, but I'm getting way ahead of myself. Right now I want
to show you a short video about Pangea. After that, I'll talk
about the oceans.
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