Once
upon a time, a very long time ago, India was all by itself, a very
large island floating along in a sea it liked to think of as the
Indian Sea. It was minding its own business, when all of a sudden—
WHAM!
India
slammed into a huge continent. The biggest continent in the world, as
a matter of fact: Asia.
India's
collision with Asia pushed up the highest mountains on the planet,
the Himalayas, just like an auto collision might push up and rumple a
car hood. And the slo-mo collision is still ongoing! India is still
pushing into the larger continental mass, still pushing up mountains.
The Himalayas are getting higher—2 centimeters per year higher.
Who'd have thunk?
The
ideas that continental and sub-continental chunks of land drift
around, that they “float” above and move around on the inner
mantle,
that continents can move from the poles to the equator or vice versa,
that seas can open up or shrink and disappear as land masses pull
away from each other or collide with each other—all these
unlikely-sounding ideas are the fruits of Alfred Wegener's brain.
Our
birthday boy was born in Germany in 1880. He grew up to be a
geophysicist (a scientist who studies the physics of the Earth, such
as its shape, its gravitational and magnetic fields, and its internal
structure) and a meteorologist (a scientist who studies climate and
weather).
Wegener
proposed continental drift in 1912. He'd noticed that the continents
seemed as if they fit together like a jigsaw puzzle, He studied rock
formations and fossils in the matching sides of the continents, and
he found a lot of evidence to back up his idea that they were once
joined together. He even came up with the idea that the Mid-Atlantic
Ridge was a place in which the Atlantic Ocean was spreading, as he
put it, “continuously tearing open and making space for fresh,
relatively fluid and hot” rock rising from the Earth's interior.
We
now know that Wegener was right! The continents once were
glommed together in one huge mass we call Pangea (from the Greek, for
“all-lands”). And the Mid-Atlantic Ridge is
formed
by
continuous seafloor spreading and upwelling of fresh magma.
However,
in 1912, nobody could come up with ideas of how this could possibly
happen, so mosts scientists did the sensible thing: They were
skeptical of Wegener's theory. (Some scientists even forcefully
attacked the idea of continental drift and promoted “permanentist”
views that the continents have always been permanently in the places
they are now.)
However,
decades later, in the 1950s, paleomagnetic data was
discovered—information about Earth's magnetic fields recorded in
ancient rocks. Long story short, this new data joined the geologic
and fossil evidence in favor of continental drift.
So
most scientists did the sensible thing: They changed their minds. By
the 1960s, Wegener was recognized as a founding father of the new
science of plate tectonics.
As
always, I am impressed by both the initial skepticism and the later
acceptance of this radical, counter-intuitive idea. Because
scientists demonstrated that they don't accept any cool sounding
idea, just willy nilly—they look for a cause or mechanism, they
look for more evidence. However, scientists also demonstrated that
they don't cling to old ideas “just 'cuz.” When the “more
evidence” arrives, they can accept the new idea. This is why
science and scientific thinking are the best ways to find out about
reality!
For
more on continental drift and lots of cool links to websites and
animations, see this earlier post.
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