Continental drift

On 6 January 1912 the German meteorologist Alfred Wegener presented a detailed theory that the continents were drifting. He postulated that there had been one supercontinent, Pangea that had broken up about 200 million years ago. The theory was not well received by geologists and the scientific community in general. They believed the continents and oceans had more permanent features. And even Wegener could not explain which forces moved the continents. He searched for more evidence, and died on an expedition to Greenland in 1930. Later the theory of plate tectonics, which includes continental drift, has been almost universally accepted. His theory was basically correct. This is how science works, when satisfactory evidence is assembled, a theory is accepted by most scientists. It is usually a hard and time-consuming activity.

The tectonic plates move today a few centimeters a year, and within 50 million years Africa and Australia will merge with Eurasia forming a new supercontinent. This new continent has already got a name - the Wegenarian cycle - in honor of Wegener. It will take a lot of work for us human beings to prepare ourselves for that great gathering. We need to learn more, but also have a lot of time to do it.

Locations of certain fossil plants and animals, form definite patterns

(shown by the bands of colors), if the continents are rejoined. 

Alfred Wegener

Background
Other scientists like Alexander von Humboldt, A. Snider-Pellegrini and others had seen how some of the continents fit well together. They made theories that the lands around the Atlantic Ocean had once been joined. Others claimed land bridges had connected the continents but that these had sunk long ago as they thought the earth was shrinking. Wegener (1880-1930) was an astronomer and meteorologist who found evidence identical fossils of plants and animals in the different continents, see map above. Wegener’s presentation to the German geological society was the first time a comprehensive and detailed theory was made. He thought that Pangea (Greek meaning “all the earth”) had incorporated most of the landmasses of the earth. In 1937 Alexander Du Toit proposed that Pangea consisted of two main landmasses Laurasia in the north and Gondwana in the south. Laurasia consisted of North America, Europe and Asia. Gondwana incorporated South America, Africa, Arabia, India, Australia and Antarctica. 

Pangaea began to break up 225-200 million years ago, fragmenting into the continents as we know them today. US Geological Survey (USGS).

Plate tectonics

New knowledge in the 1960s resulted in a new theory of Plate tectonics. Today it is estimated that Pangea   was the latest formation of supercontinents. Before that Rodinia was formed around 1 billion years ago, and Pannotia 600 million years ago. Then Pangea came into existence around 270 million years ago, there was an ocean called Tethys partially separating Laurasia and Gondwana. The only landmass which was outside Pangea was Cathaysia comprising todays North and South China.

The breakup of Pangea started around 200 million years ago when the North American plate drifted away and the North Atlantic opened up. Later, around 140 million years ago South America separated from Africa, and India left Australia and Antarctica. Then 80-30 million years ago North America separated from Europe. There was an opening between North and South America. India moved north and clashed with Asia forming the Himalayan mountains around 50 million years ago.

The Ocean currents were different than today, meaning that water was streaming between Africa and Eurasia and between North and South America.

Earth during the early Tertiary Period

Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the early Tertiary Period. Included are cold and warm ocean currents. The present-day coastlines and tectonic boundaries of the configured continents are shown in the inset at the lower right. Adapted from C.R. Scotese, The University of Texas at Arlington.

Continental plates and hot-spots 

The principal tectonic plates. Also located are several dozen hot spots where plumes of hot mantle material are upwelling beneath the plates. The world’s earthquake zones largely coincide with the boundaries of Earth’s tectonic plates. Encyclopædia Britannica, Inc.

 

Plate boundary and relation to volcanoes

Volcanic activity and the Earth’s tectonic plates. Encyclopædia Britannica, Inc.

 

Map showing the Mid-Atlantic Ridge splitting Iceland and separating the North American and Eurasian Plates. Reykjavik is the capital of Iceland, the red triangles show some of the active volcanoes including Krafla. US Geological Survey (USGS).

I am open to your comments and proposals. You may send me a message on bjarte.bjorsvik at hotmail.no

Warmly

Bjarte Bjørsvik