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Pangea and the Continental Drift
Transcript of Pangea and the Continental Drift
In 1915, the German geologist and meteorologist Alfred Wegener first thought of the theory of the continental drift
Means that parts of the Earth's crust slowly drifts on top a liquid core. The fossil record supports and gives to the theories of continental drift and plate tectonics.
Wegener hypothesized that there was a gigantic supercontinent 200 million years ago, which he named Pangea meaning "All-earth".
Continental drift is the movement of the Earth's continents across the ocean bed.
Evidence for the movement of continents on tectonic plates is now extensive. Similar plant and animal fossils are found around different continent shores, suggesting that they were once joined.
The theory of continental drift was not accepted for many years. One problem was that a plausible driving force was missing
Other geologists also believed that the evidence that Wegener had provided was not sufficient.
Alfred Wegener was the scientist who championed the Continental Drift Theory through the first few decades of the twentieth century.
Since his ideas challenged scientists in geology, geophysics, zoogeography and paleontology, it was denied.
His immediate goal was to have the concept openly discussed. Wegener did not even present Continental Drift as a proven theory.
In spite of the criticisms from several different disciplines Wegener was able to keep Continental Drift part of the discussion until his death.
To strengthen his case he drew from the fields of geology, geography, biology and paleontology. Wegener questioned why coal deposits, commonly associated with tropical climates, would be found near the North Pole and why the plains of Africa would show evidence of glaciation
Wegener presented examples where fossils of exactly the same prehistoric species were distributed where you would expect them to be if there had been Continental Drift, one species occurred in western Africa and South America, and another in Antarctica, India and central Africa.
Wegener presented very compelling arguments for Continental Drift but there were alternate explanations for some of his observations.
To explain the unusual distribution of fossils in the Southern Hemisphere some scientists proposed there may once have been a network of land bridges between the different continents.
The picture below shows the distribution of fossils on the different continents.
What does the word
The Earth's continents were eventually moved so much over millions of years that they combined into one large supercontinent
About 300 million years ago the northwestern part of the ancient continent of Gondwana (near the South Pole), came in contact with the southern part of the Euramerican continent to form one enormous continent
How and why did Pangea form?
The Break-up of
A supercontinent that existed on the Earth millions of years ago
Covered about one-third of its surface
All of the Earth's continents were connected into one large landmass
It is believed it starting forming about 300 million years ago, was fully together by 270 million years ago and began to separate around 200 million years ago
From the Greeks
Means “all lands”
The term was used when a scientist named Alfred Wegener noticed the shapes of the Earth's continents could fit all together like a jigsaw puzzle
Developed a theory of continental drift to explain why the continents looked the way they did
Wegener first used the term Pangea at a symposium in 1927 focused on that topic
The Angaran continent, located near the North Pole, began to move south and it came in contact with the northern part of the Euramerican continent to form the large supercontinent, Pangea, about 270 million years ago
Pangea covered around one-third of the Earth's surface and it was surrounded by an ocean that covered the rest of the globe. The ocean was known as Panthalassa.
Split up about 200 million years due to the movement of the Earth's tectonic plates and mantle convection
A rift of new material caused it to separate just like when Pangea was being formed by being pushed together due to the movement of the Earth's plates away at rift zones.
Scientists believe that this happened due to a weakness in the earths crust by a new rift
When the weak spot took place, magma began to push through and created a volcanic rift zone. As more magma pushed through, the rift zone grew so large that it formed a basin and Pangea began to separate.
When Pangea split, oceans formed as Panthalassa rushed into the newly opened areas
180 million years ago the central Atlantic Ocean was formed
140 million years ago the South Atlantic Ocean was formed