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Continents: How many exist?

In the USA, in History class, we learn that Europe and Asia are separate continents. Yet in other nations’s history classes, they’e taught that Europe and Asia are one: Eurasia.

In Earth Science we define a continent by the boundaries of tectonic plates – so in this view, there is just one continuous continent, Eurasia.

Who is right? Or can both points of view be justified? Here are questions that you need to ask :

* Why would anyone describe Europe as being a distinct continent to begin with?

* Do Europe and Asia have natural geological features that divide them?

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Ancient scholars believed that there were three continents

The three were Asia, Europe and Africa. The Israelite city of Jerusalem was usually shown in the center.

This idea was popularized with the creation of the T-O map, in the 7th-century, by Isidore of Seville (c. 560 – 636), Archbishop of Seville.

This image is from his classic work, The Etymologiae. The division was drawn in a “T” shape, contained in a larger, “O” shaped Earth. Isidore knew that the world was spherical, not a flat circle. Educated people knew this ever since this was proven by the ancient Greeks.

This T and O map, from the first printed version of Isidoor's Etymologiae. It identifies the three known continents as populated by descendants of the biblical characters Sem (Shem), Iafeth (Japheth) and Cham (Ham). http://en.wikipedia.org/wiki/T_and_O_map

This T and O map, from the first printed version of Isidoor’s Etymologiae.
It identifies the three known continents as populated by descendants of the biblical characters Sem (Shem), Iafeth (Japheth) and Cham (Ham).
http://en.wikipedia.org/wiki/T_and_O_map

Isidore knew that there must be more ocean and land on the other hemisphere (“other half”) of the world, but he had no information on them, and as such did not attempt to draw this.

Could people travel from one hemisphere to the next? Yes, and many people did this in antiquity. But some early medieval scholars – who didn’t travel – in Europe imagined that the equator was so hot, that this would be impossible.

Some people even imagined that no human beings could exist on the “other side” of the world (what today would include Australia, southern Africa, and all of the Americas.)

“St. Augustine, arguing from a position of scriptural inerrancy, wrote in his City of God “it is too absurd to say, that some men might have taken ship and traversed the whole wide ocean, and crossed from this side of the world to the other, and that thus even the inhabitants of that distant region are descended from that one first man [Adam].”

(St. Augustine, city of God)
– http://en.wikipedia.org/wiki/Antichthones

A few centuries later, European realized that it was possible to safely cross the equator; they then realized that human beings could travel anywhere on the world. However, Europeans still drew the known world on T-O maps for some time. This ingrained in them the idea that Europe and Asia must be separate continents.

Ideal reconstruction of medieval world maps (from Meyers Konversationslexikon, 1895) http://en.wikipedia.org/wiki/T_and_O_map

Ideal reconstruction of medieval world maps (from Meyers Konversationslexikon, 1895)
http://en.wikipedia.org/wiki/T_and_O_map

The Bünting Map is an historic mapped illustration of the world. “It was drawn by the German Protestant pastor, theologist and cartographer Heinrich Bünting. The map was published in his book Itinerarium Sacrae Scripturae – “Travel through Holy Scripture” in 1581. “

– http://en.wikipedia.org/wiki/B%C3%BCnting_Clover_Leaf_Map

Earth Science view of continents

Today we define a continent as being a large mass of land, above water, built of one tectonic plate. The six major continents would then be:

1. North America 2. South America 3. Eurasia 4. Africa 5. Australia 6. Antarctica

There are also a few subcontinents:

The Arabian peninsula- Includes Saudi Arabia, Yemen, Oman, Qatar, Bahrain, Kuwait, and the United Arab Emirates

The Indian subcontinent –  Includes India, Pakistan, and Bangladesh

Greenland is obviously huge, but doesn’t qualify as it’s own continent, as it is a part of the North American tectonic plate.

tectonic_plates_boundaries

Here is what Eurasia looks like:

Natural features separating Asia and Europe

“Evidently the first man to define the eastern continental boundary between Europe and Asia pretty much as it exists today is Philip Johan von Strahlenberg (1676–1747), a Swedish army officer, explorer, and scholar of German descent.”

“As defined in his book Das nord- und ostliche Theil von Europa und Asia (The north and east part of Europe and Asia) (Stockholm, 1730), which was translated into English, French, and Spanish, Strahlenberg’s border followed the chain of the Ural Mountains north-to-south, then the Emba River to the north coast of the Caspian Sea before passing through the Kuma-Manych Depression to the Black Sea.

This Depression, named after two rivers, lies just north of the Caucasus Mountains which are today regarded as the true boundary.”

http://www.counter-currents.com/2011/08/europes-continental-boundaries/

europe-map-of-europe-physical-relief-wikipedia Ural Caucasus Mountains

Did we discover a missing continent, under the Earth? 🙂

Farallon plate, Karin Sigloch *08
University of Munich, Department of Earth and Environmental Sciences

This is a three-dimensional structure of the Earth’s mantle under western North America, down to a depth of 1500 kilometers.

Seismic tomography uses waves generated by naturally occurring, strong earthquakes to probe and “illuminate” the planet’s deep interior.

seismic_waves_usgs

Hundreds of thousands of measurements were combined to create this 3-D reconstruction, using algorithms similar to those that deliver 3-D images of the human body in medical tomography.

The Pacific coastlines and mountainous western states are plotted above an expansive, seismically fast structure, colored in purple, known as the Farallon plate.

It is a vast piece of ancient ocean floor that has been slowly sinking back into the mantle over the past 150 million years. The tectonic stresses caused by the Farallon’s movements deep underground have thrust up the mountain peaks and plateaus of the West. They continue to drive its volcanoes and earthquakes, thus shaping the surface appearance of an entire continent.

The Farallon Plate was an ancient oceanic plate that began subducting under the west coast of the North American Plate—then located in modern Utah—as Pangaea broke apart during the Jurassic period. It is named for the Farallon Islands, which are located just west of San Francisco, California.

Over time, the central part of the Farallon Plate was completely subducted under the southwestern part of the North American Plate. The remains of the Farallon Plate are the Juan de Fuca, Explorer and Gorda Plates, subducting under the northern part of the North American Plate; the Cocos Plate subducting under Central America; and the Nazca Plate subducting under the South American Plate.

http://en.wikipedia.org/wiki/Farallon_Plate

‘Lost’ Tectonic Plate Found Beneath California
http://www.livescience.com/27994-lost-tectonic-plate-california.html

earthscope education and outreach: Seismic Tomography
http://www.iris.edu/hq/files/programs/education_and_outreach/lessons_and_resources/docs/es_tomography.pdf

How does seismic tomography work? Incorporated Research Institutions for Seismology

http://www.iris.edu/hq/programs/education_and_outreach/animations/7

http://www.michw.com/2013/04/seismic-tomography-the-easy-way/

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