What is the driving force behind the movement of the continental plates?

Not everyone agrees on why the continental plates move across Earth but there are some theories. In general, the continental plates are made of light material that floats on the heavier, molten material of Earths interior (called the mantle). As the upper part of the mantle circulates and moves, it slowly carries the plates around the planet.

What are the consequences of continental plate movements?

As the term implies, the movement of the continental plates changes the positions of the continents. Along the continental boundaries, volcanoes and mountains form as the plates interact with each other. Some continents slowly crash into one another, forming huge mountain chains, such as the Himalayas in Asia (from the collision of the Indian and Asian plates). Other plates slide under one another in areas called subduction zones. The Andes Mountains are the result of a subduction zone between the Nazca and South American plates. Still other plates slip right by one another, such as the Pacific and North American plates. In this case, the slipping of the plates creates the San Andreas fault in California.

But there are other consequences of continental plate movement. In particular, this process also opens and closes the seas, changing ocean currents and thus climates around the world. In addition, volcanoes can form as plates sink under each other, and earthquakes can occur.

Continental plate movements have a variety of effects upon the planet, ranging from shifts in temperature to devastating earthquakes. Plate tectonics affect us today, just as they affected the dinosaurs millennia ago (iStock).

What did our planet look like at the start of the Triassic period?

Similar to today, most of the planet during the Triassic period was covered by ocean, but the distribution of the landmasses was not the same. Scientists believe there was essentially one large expanse of water called the Panthalassa Ocean. It surrounded the one very large landmass, or supercontinent, called Pangea, meaning all Earth.

This giant landmass straddled the planets equator roughly in the form of a C; the smaller body of water enclosed by the C on the east was known as the Tethys Sea (or Tethys Ocean). Only a few scattered bits of continental crust were not attached to Pangea, and lay to the east of the larger continent. They included pieces of what we now call Manchuria (northern China), eastern China, Indochina, and bits of central Asia. In addition, the sea level was low, and there was no ice at the polar regions.

As Pangea began to break up, it formed two smaller supercontinents that scientists have named Laurasia and Gondwanaland (based on a map from the U.S. Geological Survey).

What led to the original formation of the supercontinent Pangea?

The same process that would eventually break apart Pangea led to its formation the continents seemingly moving around the planet like icebergs on an ocean. There were two large landmasses on Earth during the Paleozoic era Laurasia (North America and Eurasia) to the north of the equator, and Gondwanaland (or Gondwana, including South America, Africa, India, Antarctica, and Australia) to the south of the equator. These two continents slowly collided during the Late Paleozoic era, forming the supercontinent of Pangea. By the beginning of the Mesozoic era, Pangea was still the only true continent on the planet.

How did the supercontinent Pangea change during the Triassic period?

In the Early Triassic period, Pangea gradually began to break apart into two major continents again, the result of a seafloor-spreading rift. (This rift was similar to todays Mid-Ocean Ridge in the Atlantic Ocean, a volcanic seam that continues to spread, and along which the volcanic island of Iceland was born.) The Triassic rift extended westward from the Tethys Sea across what is today the Mediterranean Sea. The action of this rift separated northern Laurasia from southern Gondwanaland, which would eventually lead to the opening of the proto-Atlantic (or early Atlantic) Ocean. As North Africa split from southern Europe, there was a gradual rise in sea level that flooded south and central Europe.

Towards the Middle and Late Triassic periods, the spreading rift between North Africa and Europe grew westward, and it began to separate North Africa from the eastern part of North America. The resulting rift valley was the first true stage in the formation of the proto-Atlantic Ocean.

 
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