How Pangaea Became 7 Separate Continents

Wegener called the ancient supercontinent Pangaeameaning "all lands" in Greekand he said it was bordered by Panthalassathe universal sea. He claimed the lands separated 250 million years ago by the process of continental driftwhich means the continents just slowly fractured and went their separate ways.

But simply drifting apart seemed too weak of an answer. It didn't seem possible for the continents to just move along the ocean floor. Something stronger had to be at work.

Did something drive a rift through the continents and force them apart? And could another supercontinent emerge? Figuring out how the continents drifted apart took geological society on a magical mystery tour to the ocean floor.

Although scientists agreed with Wegener that there had been a supercontinentthey disliked the reasoning behind continental drift. To really learn what was behind the breakup of Pangaeathey would need to venture all the way to the ocean floor.

From the 1950s to the 1970sscientists made some important discoveries about the ocean's crust.

Some of the first breakthroughs came in the field of paleomagnetismas scientists studied the Earth's magnetic fields. The magnetic properties of rocks are classified either as normalmeaning that they have the same polarity as the current magnetic fieldor as reversedmeaning that the polarity is opposite the Earth's magnetic field.

This state of polarity becomes locked in when rock is formed. As scientists looked at the patterns of magnetic rockthe layers didn't quite align the way that they were supposed tosuggesting that the magnetized rock and the continents that surrounded it had moved.

What scientists didn't know was why they had moved.

Tectonic Plate Boundaries

The symmetrical striping pattern of the rock provided some more cluesand so did the topography of the ocean's floor. When scientists began mapping the ocean floorit looked a lot younger than expected.

For something as old as the Earthscientists expected to see a lot more built-up sediment. They also found oceanic mountain ranges.

Sea Floor Spreading

Paleomagnetic studies revealed that on either side of the mountain rangesthere was a symmetrical magnetic striping. The oceanic map and the magnetic striping were explained in 1962when a scientist named Harry Hess conceived the idea of seafloor spreading. Seafloor spreading is the process by which magma within the Earth's crust emerges at the mountain ranges and separates the sea floor.

The magma creates a new section of sea floorwhich explained why the oceanic crust looked so young: It was continually emerging as a new floor. The newest rock was closest to the mountain rangewith older rock located farther awayand each new layer reversed the magnetic polarityexplaining the striping.

When scientists first realized that new ocean floor was regularly emergingthey thought this must mean that the Earth was expanding. But insteadthey realized the ocean floor was like a conveyor beltand that as the new ocean floor emergedsome of the old ocean floor disappeared into oceanic trenches through the process of subduction.

Earthquakes and Volcanic Eruptions

Seismologists were also noticing at about this time that volcanic activity and earthquakes occurred near the spreading ridges and the oceanic trenches. This geological survey evidence suggested that although the continents were movingthe force did not come from the continents themselvesbut rather from the ocean's crust.

These moving slabs of earth were dubbed platesand their movements cause many natural eventsincluding earthquakesvolcanoes and mountain formations. The study of these plate movements came to be known as plate tectonics.

The theory encapsulates both Alfred Wegener's ideas about continental drift and Harry Hess' discoveries about seafloor spreading. ThusWegener's ideas about Pangaea were finally explained.

The continents rest on plates made of a layer of the Earth's crust and its mantleknown collectively as the lithosphere. Plates are different sizeswith some plates more than 124 miles (200 km) thick [source: Kious]. Below the lithosphere is a fluid layer of rock called the asthenosphere.

The plates are rigid slabs almost floating along in the asthenospherebut scientists still aren't sure what causes the plates to move. They know it's somehow related to convection currents in the continental crustin which hot materials rise upward as cooler materials flow downwardbut they haven't figured out the precise relationship.

Scientists do know four different ways the plates movethough.

Now that we know a little bit about how plates movewe can turn again to supercontinents. The planet the oldest supercontinent is known as Rodiniaand it formed about 1 billion years ago [source: Encyclopædia Britannica].

The evidence for all of the supercontinents is limited because the sea floor is always regenerating itselfso Pangaeathe youngesthas the fullest geologic record.

Before Pangaea became a supercontinentit existed as different continents. Three large continental plates came together to form what's now the Northern Hemisphereand that landmass merged with what is now the Southern Hemisphere. Pangaea existed during the late Paleozoic and Mesozoic erasor about 200 million years ago [source: Oreskes].

Pangaea Births All the Continents

Pangaea existed for approximately 100 million years before it began to divide into all the continents we know and love today. Firstthe continents broke into two large landmasses:

Laurasia split into North America and Eurasiaand Gondwanaland produced AfricaAntarcticaAustralia and South Americawith some of the pieces rotating slightly as they separated.

As the continents broke away from Pangaeathe Paleo Tethys Ocean formedeventually growing into what we call the Indian Ocean today. The two continents of North and South America split from Europe and Africa and headed far westwardwith the water filling in the gap becoming the Central Atlantic Ocean.

The plates continue to move todaywith the most action these days located at the East African Rift. Some geologists think that if they keep movingthe three plates that meet at the African coastline will separatecausing the Indian Ocean to flood the area and separating the Horn of Africa from the mainland [source: Kious]. (In shortAfrica is splitting in two.)

How fast does all this happen? The magnetic striping around the places where the sea floor spreads provide a way to measure the continental movementwhichin some placesnears a rate of almost 4 inches (10 centimeters) per year [source: Skinner].

The Mid-Atlantic Ridge moves less than 1 inch (2.5 centimeters) a yearso over millions of yearsthe South Atlantic Ocean has gone from being a tiny inlet to the size we know it today [source: Kious]. Scientists like to compare the speed at which continents move to the speed at which our fingernails grow [source: Reina].

Although the movements are slowAfrica is moving toward southern Europeand Australia and south China will collide one day [source: Encyclopædia Britannica]. These are the first movements toward another supercontinent.

Scientists predict the next supercontinent will reconnect in another 250 million years. This process of landmasses coming together and spreading apart is now known as the supercontinent cycle.