Posted on November 23, 2021
This is an update of my post published on November 23, 2010:
Antarctica is continent covered by ice about a mile thick. Despite the fact that the oceans surrounding the continent team with life—penguins and seals, giant squid and whales, its frozen interior lands are almost lifeless.
But it wasn't always so!
On this day in 1969, a team of paleontologists discovered the fossilized bones of Lystrosaurus, a therapsid reptile (these are the ancestors of modern mammals) that lived 200 million years ago. It was a creature that lived in warm climates.
Whaaat?
Remains of Lystrosaurus had earlier been found in southern Africa and Asia, so the new finding of Antarctic dinosaurs proved that the three continents had once been joined in a super-continent we call Gondwana. The portion of this supercontinent that is now Antarctica was located straddling the equator, which explains its mild temperatures, but when Godwanna broke up millions of years ago, and the various chunks of land drifted about, Antarctica drifted to the polar location we see today.
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| Before there was Gondwana - plus another supercontinent called Laurasia - there was Pangea, one huge all-the-world's-lands-in-one-super-continent. |
The theory that continents have drift around on the surface of the Earth is called, naturally, continental drift. Alfred Wegner first proposed continental drift in 1912, and most scientists were skeptical of the idea. However, evidence from the geographical shape and geological content of the continents, tectonic forces in the Atlantic Ocean (which even today is getting measurably wider as the ocean-floor plates pull away from each other), plants and animals, and fossil remains, data on the flip-flop of the planet's magnetic poles—all of that evidence has shown Wegner's idea to be correct. Also, geologists have come up with a mechanism to explain how continents can move around: plate tectonics.
Did you know...?
Way back in the 1700s, Benjamin Franklin noticed that Africa and South America seem to fit together like jigsaw puzzle pieces, and he suggested that they were once connected. Of course, unlike Wegner, Franklin did not collect comparative data to try to prove the point.
The Earth's magnetic field has “flip-flopped” many times in the past, with North becoming South and vice versa. This field reversal doesn't happen overnight, but instead takes thousands of years. And it may be that it is about to flip soon! Apparently the North-South switcheroo happens once every 250,000 years, give or take a few hundred years—but it has been 750,000 years since the last pole reversal! We are loooong overdue! Also, right now Earth's magnetic field is lessening year after year—and it is believed that this is a first sign of an oncoming magnetic field flip.
Find out more...
Here is a video that shows continental drift from 200 miliion years ago until now.
Did you know that the continents are STILL drifting? Here's what one of the possible ways the Earth could change in the next 250 million years! But there are various theories about where the continents are heading:
Older students might like to complete a lesson on the fossils of Antarctica. There are links to several interesting websites/articles here.
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