It was n’t until 1912 that meteorologist Alfred Wegener hypothesized that Earth ’s continents had once been fall in as a supercontinent that we now callPangea .
Wegener had point out that the border of the continent matched up and fit together , almost like a giant reciprocating saw puzzle , and this determination lead him to discover a missing bit of Earth history .
There were other clues as well ; match rock andfossilswere found in countries separated by the Atlantic and Indian oceans . Tropical plant fossil were also found in southern polar regions ( and frailty versa ) , betoken that the continents of planetEarthmight not have always been in their current positions .
Discovering Pangaea
Wegener call the ancient supercontinent Pangaea , meaning " all lands " in Greek , and he enounce it was bordered by Panthalassa , the universal ocean . He claimed the lands tell 250 million age ago by the process of continental purport , which mean the continents just easy fractured and hold out their separate ways .
But simply drifting aside seemed too weak of an answer . It did n’t seem possible for the continents to just move along the sea floor . Something stronger had to be at work .
Did something drive a rift through the Continent and force them apart ? And could another supercontinent emerge ? compute out how the continents drifted apart took geologic beau monde on a magical mystery turn to the sea base .
Pangaea and Plate Tectonics
Although scientist agree with Wegener that there had been a supercontinent , they dislike the abstract thought behind continental impetus . To really read what was behind the breakup of Pangaea , they would need to venture all the way to the sea floor .
From the 1950s to the 1970s , scientists made some crucial discoveries about the ocean ’s crust .
Some of the first breakthrough came in the field of paleomagnetism , as scientists contemplate the Earth’smagnetic fields . The magnetized properties of rocks are classified either as normal , mean that they have the same sign as the current magnetised field of force , or as reversed , meaning that the polarity is opposite the Earth ’s charismatic field .
This state of matter of sign becomes locked in when rock’n’roll is formed . As scientist looked at the patterns of magnetic rock candy , the layers did n’t quite line up the mode that they were think to , suggest that the magnetized rock and the continents that surrounded it had moved .
What scientists did n’t know waswhythey had moved .
Tectonic Plate Boundaries
The symmetric discase pattern of the rock-and-roll ply some more cue , and so did the topography of the sea ’s level . When scientists began mapping the ocean storey , it looked a lot youthful than expected .
For something as sure-enough as the Earth , scientist expected to see a destiny more progress - up sediment . They also found oceanic stack ranges .
Sea Floor Spreading
Paleomagnetic studies revealed that on either side of the pot ranges , there was a proportionate magnetic striping . The oceanic mathematical function and the magnetic striping were explained in 1962 , when a scientist named Harry Hess conceived the estimate of seafloor go around . Seafloor scatter is the process by which magma within the Earth ’s crust emerge at the wad ranges and separates the sea floor .
The magma create a unexampled surgical incision of sea floor , which explained why the oceanic crust looked so young : It was continually emerge as a unexampled floor . The newest rock was close to the lot range , with older tilt located further off , and each new bed reversed the magnetic sign , explaining the striping .
When scientist first realise that new ocean trading floor was on a regular basis emerge , they remember this must intend that the Earth was extend . But instead , they realized the ocean floor was like a conveyor whang , and that as the novel sea trading floor emerged , some of the old ocean flooring disappeared into oceanic trenches through the unconscious process of subduction .
Earthquakes and Volcanic Eruptions
Seismologists were also note at about this time that volcanic activity andearthquakesoccurred near the distribute ridge and the oceanic oceanic abyss . This geological survey evidence suggested that although the continents were moving , the force did not come from the continents themselves , but rather from the ocean ’s crust .
These proceed slabs of ground were nickname shell , and their social movement have many natural issue , including earthquake , volcanoesand mint formations . The subject field of theseplate movementscame to be have a go at it as denture tectonics .
The theory encapsulate both Alfred Wegener ’s ideas about continental movement and Harry Hess ' discovery about seafloor circulate . Thus , Wegener ’s estimate about Pangaea were finally explain .
Plate Movement and the Pangaea Theory
The continents rest on plates made of a layer of the Earth ’s crust and its mantle , fuck jointly as the lithosphere . plate are different sizes , with some plate more than 124 sea mile ( 200 km ) thick [ source : Kious ] . Below the geosphere is a mobile layer of rock and roll called the asthenosphere .
The plates are stiff slab almost float along in the asthenosphere , but scientist still are n’t sure what causes the plates to move . They know it ’s somehow related to convection currents in the continental crust , in which raging material rise up as cooler material flux downward , but they have n’t figured out the accurate relationship .
scientist do know four different way the plates move , though .
Now that we know a footling mo about how plate move , we can turn again to supercontinents . The planet the oldest supercontinent is be intimate asRodinia , and it formed about 1 billion old age ago [ source : Encyclopædia Britannica ] .
The grounds for all of the supercontinents is limited because the ocean floor is always regenerate itself , so Pangaea , the youngest , has the fullest geological record .
Before Pangaea became a supercontinent , it be as different continents . Three large continental plates came together to form what ’s now the Northern Hemisphere , and that landmass immix with what is now the Southern Hemisphere . Pangaea existed during the previous Paleozoic and Mesozoic eras , or about 200 million years ago [ rootage : Oreskes ] .
Pangaea Births All the Continents
Pangaea existed for approximately 100 million eld before it began to dissever into all the continents we fuck and have sex today . First , the continents brokeinto two prominent landmasses :
Laurasia cleave into North America and Eurasia , and Gondwanaland produced Africa , Antarctica , Australia and South America , with some of the piece rotate slimly as they separated .
As the continents broke forth from Pangaea , the Paleo Tethys Ocean formed , eventually growing into what we call the Indian Ocean today . The two continent of North and South America break up from Europe and Africa and headed far westward , with the pee filling in the break becoming the Central Atlantic Ocean .
The Supercontinent Cycle
The plates go on to move today , with the most activity these days located at the East African Rift . Some geologists cerebrate that if they keep move , the three plates that foregather at the African coastline will classify , causing the Indian Ocean to inundate the expanse and separating the Horn of Africa from the mainland [ source : Kious ] . ( In unforesightful , Africa is splittingin two . )
How fast does all this happen ? The charismatic ransack around the places where the sea floor paste supply a direction to measure the continental front , which , in some places , nears a pace of almost 4 inches ( 10 centimeters ) per yr [ source : Skinner ] .
The Mid - Atlantic Ridge moves less than 1 inch ( 2.5 centimeter ) a yr , so over millions of years , the South Atlantic Ocean has go from being a tiny intake to the sizing we recognize it today [ source : Kious ] . scientist like to compare the speed at which Continent move to the speed at which our fingernails grow [ source : Reina ] .
Although the movement are slow , Africa is moving toward southern Europe , and Australia and south China will collide one solar day [ generator : Encyclopædia Britannica ] . These are the first movements toward another supercontinent .
scientist predict the next supercontinent will reconnect in another 250 million year . This process of land mass coming together and spreading apart is now known as the supercontinent bike .
