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Nature & Outdoors

Plate Tectonics: Are Continents and Oceans Moving?

Since Earth formed, the continents have been in constant motion. This motion is very slight and occurs over millions of years, but exists nonetheless. One of the earliest ways geologists thought continents moved over time was known as continental drift. This theory was set forth in 1912 by Alfred Wegener and also explained why similar plant fossils and rock formations were found on different continents. Wegener believed that the continents moved through the ocean without any underlying mechanism. While some of Wegener’s beliefs were correct—such as the previous existence of a supercontinent known as Pangaea—the theory of continental drift was eventually replaced by that of plate tectonics.


Today, the theory of plate tectonics has been widely accepted. Continents rest on massive slabs of rock known as tectonic plates which are constantly moving. Seafloor spreading zones are some of the most constantly changing sites of tectonic activity. Slowly, but surely, the continents and oceans are moving.


So, what does this mean for the future of the planet? Some scientists believe that Earth might once again have just one continent, but this won’t happen for another 250 million years. This motion may not have a large effect on human life as it is now, but it's interesting to understand where humans came from and where the future of Earth is going.



 width= What Was Pangea?


Alfred Wegener believed that all of Earth’s continents were once one enormous landmass known as Pangaea. Wegener used biology, botany, and geology to describe the idea of Pangaea and continental drift.


Fossils of the extinct Lystrosaurus , a lizard-like anima, have been found in South Africa, India, and Antarctica. Fossils of the extinct fern Glossopteris have been found in both the polar circle and the tropics. Other plant fossils of tropical plants have been found in Norway, suggesting that it once had a tropical climate. Fossils of the extinct reptile Mesosaurus are only found in South America and southern Africa.


The Appalachian Mountains of the eastern United States and the Caledonian Mountains of Scotland seem to be geologically related. The east coast of South America and the west coast of Africa also seem to fit together perfectly. How could all of this be, if all of the continents weren’t once part of one large landmass? 1



Separation Into Different Continents


Scientists determined that the expansive supercontinent was actually made up of two smaller continents that connected at the equator. Laurasia, located in the Northern Hemisphere, encompassed what is now North America, Europe, Greenland, and most of Asia. Gondwanaland, located in the Southern Hemisphere, encompassed what is now South America, Australia, India, and Antarctica. 2


Scientists believe that Pangaea existed approximately 250 million years ago. By approximately 200 million years ago, the supercontinent began to break into smaller continents via continental drift. Although this process was slow, over millions of years Pangaea separated into the continents that you know today. These pieces slowly moved away from each other into the locations you are familiar with.


Nowadays, scientists believe that Pangaea isn’t the only supercontinent in the history of the earth. It is thought that several supercontinents have formed and separated over billions of years. Two of these supercontinents are Rodinia, which existed over a billion years ago, and Pannotia, which formed approximately 600 million years ago. Other supercontinents are known as Ur, Kenorland, and Nuna.



 width= Replacing Continental Drift with Tectonic Activity


Wegener believed that the continents moved through the ocean at random and that the rotation of the earth caused the movement. In this theory, he claimed that these landmasses were drifting across the earth, sometimes crashing into each other.


Today it is known that the movement of the continents is not random, and it is still happening today. Continents rest on tectonic plates which are constantly moving and interacting with each other. Tectonic activity is most prevalent in giant rift valleys and seafloor spreading zones. Scientists and the general public did not accept these until the mid-1960s.



Rift Valleys


Rift valleys are places where a continent is slowly ripping itself apart. The Great Rift Valley system is a series of faults and other tectonic activity that stretches from southwest Asia to the Horn of Africa. The continent of Africa will eventually split in two due to this Rift valley.



Seafloor Spreading Zones


In seafloor spreading zones, molten rock rises from the earth’s crust to the bottom of the sea, adding new seafloor known as oceanic crust. This process happens mostly along mid-ocean ridges, which are giant underwater mountain ranges. As the seafloor continues to expand, continents that rest on opposite sides of the range begin to move away from each other.


The Mid-Atlantic Range separates the tectonic plates of North America and Eurasia. Due to seafloor spreading, these continents move away from each other at a rate of approximately an inch per year.



An Interesting Discovery


In 2017, three tiny crystals were found on the island of Mauritius. While this may not seem significant, these crystals date back approximately 2.5 to 3 billion years. The island of Mauritius, by comparison, formed approximately 9 million years ago. How did crystals billions of years old end up on an island that isn’t even one billion years old? 3


Lewis Ashwal, a scientist from the University of the Witwatersrand in South Africa, believes that the crystals belonged to a drowned landmass. When Mauritius was formed by lava from undersea volcanoes, these crystals were brought up to the surface.


Scientists believe these crystals came from an ancient continent hidden deep within the Indian Ocean. This continent has been called Mauritia and may be as large as Japan. As Pangaea split into pieces, Mauritia ended up sinking beneath the ocean. It is interesting to speculate about the many different fossils and crystals that may appear in other places across the world from sunken continents.



 width= What Does the Future Hold?


Because of current knowledge about tectonic activity, oceans and continents are constantly moving. Scientists have found that Australia is slowly moving North, perhaps one day colliding with Japan and eastern China.


Africa is slowly moving east towards Europe, where it may create a new, large-scale mountain range. Interestingly enough, scientists are at a crossroads when it comes to the future of the Americas. Some speculate that the Atlantic Ocean will eventually stop growing and will one day begin to shrink again. Others believe that the Atlantic will continue to expand.


It can be difficult to determine exactly what course the future will take. If the Atlantic starts to shrink, the eastern Americas, Africa, and Europe will all suffer from frequent earthquakes and volcanic eruptions. The mountains of the eastern United States will transform into large, snow-covered peaks that occasionally erupt. Newfoundland will eventually collide with Spain, while Brazil will eventually run straight into South Africa.


On the other hand, if the Atlantic Ocean continues to expand, the Pacific Ocean will begin to shrink. This will cause the Americas to eventually crash into Asia. Scientists believe that this crash will split each continent into smaller pieces which will spread away from each other, meeting again on the other side of the world.


Regardless of whether the Atlantic continues to grow or begins to shrink, scientists believe that the next supercontinent will eventually form at the equator. In the next 250 million years, there may be supercontinent—one that is being referred to as Pangaea Ultima.


Photo credits: VicPhotoria/shutterstock.comMopic/shutterstock.com, RashevskyiViacheslav/shutterstock.com, Photopictures/shutterstock.com


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