Like many important theories in science, plate tectonics, the concept that the Earth’s surface is like a cracked eggshell with each piece floating on a convective mantle of molten rock, was once considered a crackpot idea. But sometimes crackpot ideas are right. Plate tectonics now underpins all of geology, much like the Big Bang Theory is the foundation of astronomy and astrophysics.
The theory of plate tectonics was deduced in the mid-20th century by a handful of scientists and cartographers who wondered why, for example, the eastern coast of South America complemented so precisely the shape of the western coast of Africa, and why fossils of long-extinct animals were found scattered on different continents separated by wide oceans, and why volcanoes and earthquakes are far more common in some locations than others, and why fossilized marine creatures are sometimes found at the tops of mountains. Before plate tectonics, these observations were a mystery. After plate tectonics, they all started to make sense.
The plates of the Earth’s crust have been on the move since our planet first cooled some 3.5 billion years ago. These plates have pulled apart, come back together to form supercontinents, and pulled apart again in a roughly 300-million-year cycle. And the plates are still on the move which is why, for example, the city of Los Angeles will one day drift northward past San Francisco on its way to Alaska in about 50 million years.
The churning surface of the Earth’s surface might even be a prerequisite for the formation life. Earth is the only terrestrial planet in the solar system with life, and the only such planet with significant plate tectonic activity. Coincidence? Some scientists think not. The release of carbon dioxide by volcanoes formed by plate tectonics may help regulate the Earth’s temperature and keep it warmer than it would otherwise be. And moving plates may have helped stir and mix the raw material for life in our planet’s earliest days.
Geologists have gotten quite good at tracking the movements of the many plates that make up the Earth’s surface, and it’s now possible to model the shape and motion of the Earth’s continents over hundreds of millions of years. So one enterprising naturalist, Ian Webster, created an online app that uses state-of-the-art geological data to model the changing surface of the Earth with enough accuracy to track a particular location on Earth any time over the past 700 million years, a time when most of the continents of the Earth were clustered in a single supercontinent called Rodinia.
Here’s the link: http://dinosaurpictures.org/ancient-earth
This online app is great fun to play with. Type in your address at the top, pick the time in the past, and the app shows the location of your current address. At one time, you might find yourself at the bottom of an ocean, then in the middle of a supercontinent a hundred million years later. As time moves closer to the present day, the Earth begins to look a little more familiar. In my case, I was delighted to find the continent of Africa just across a nearby river from my Maryland home about 250 million years ago during the early Triassic. Senegal was about the same distance as Chicago, and the Atlantic Ocean was still a twinkle in the Earth’s eye.
Have some fun with this little app, and share it with the curious around you.
All these ‘crackpot ‘ ideas… plate tectonics, the Big Bang, evolution, the Standard Model. All crazy, and yet all verified by observation and all pointing us to a deeper understanding of how nature works.
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