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The modern-day formation of Earth's continents is explained by the theory of plate tectonics. This geological theory, which became widely accepted in the 1960s, "holds that the surface of Earth is composed of a dozen or so huge crustal slabs that float on a sea of partially molten rock." The seven continents rest upon these floating slabs, which move in various directions and thus bump into and move apart from each other over and over again (albeit at an extremely slow rate).
These movements drastically affect the way our planet looks over an incredibly long span of time. On a relatively small scale, the clashing of plates forms incredible mountain ranges. On a larger scale, it affects the placement of entire continents on the globe. In the distant past, some 200 million years ago, the continents were actually compiled into one land mass, which scientists refer to as Pangea. Using the same techniques that enabled them to form the concept of that distant super continent, geologists can also predict the placement of the continents far into the future.
Surprisingly, it's quite easy for scientists to envision Earth's appearance 50 million years from now. After all, it's a very small span of time in comparison to our planet's age. The big changes that are predicted to occur in 50 million years' time are:
- The disappearance of the Mediterranean Sea. This will be caused by Africa's movement north into Europe, which will eliminate the body of water between them.
- The movement of the Pacific plate up the West coast of North America. In 10 million years' time, "Los Angeles will be abreast of San Francisco." 50 million further on from that, and Southern California will be up in the waters of Alaska. You might recall that Los Angeles rests on the San Andreas Fault line, which is why it will be pushing northward, apart from the rest of the Western coastline.
So, in 30 million years, Earth will be in the midst of moving towards those massive changes. Distant changes that may be just beginning to develop at that time include Antarctica's drift into the Indian Ocean and Australia's progression north towards Asia.
Ultimately, geologist Dr. Scotese predicts, the globe will revert to a Pangea-esque formation again, which should culminate 200 million years from now (though others in his field argue that seeing that far into the future produces as accurate results as predicting the weather years from now). You can read more about his hypothesis of "Pangea Ultima" in a 2007 New York Times article cited below. The video at the second link will also provide a good visual of the movement of Earth's tectonic plates for you.
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