Although the continental drift theory had not been developed until the 1960s, it was expounded in the early 20th century by a revolutionary young German scientist named Alfred Wegener.
This young scientist had noticed that the “coasts of Africa and South America seemed to fit together like puzzle pieces” even though they were separated by the vast Atlantic Ocean.
So what does the continental drift theory say?
Noting that the African and South American coasts seemed to fit together like a puzzle, Wegener suggested that these continents had once been joined and for some reason had then drifted thousands of miles apart and formed the Atlantic Ocean.
Alfred Wegener throughout history was not the first to realize this coincidence and to make that observation, however, he was the first scientist to delve into a deeper investigation.
Wegener then began to study all the maps of the world and the continents and realized that there were many places and continents that fit together almost perfectly like puzzle pieces.
So this led him to a conclusion.
Continental Drift Theory Conclusion
Alfred Wegener then formed a map where he joined all the places and continents that fit almost perfectly, this union of continents millions of years ago would have formed what is known as a supercontinent.
To this supercontinent Currently it is called “Pangea” which means “all lands” and indicates that once all the continents were one. The northern part of Pangea is commonly called Laurasia and the southern part Gondwanaland.
Therefore, it is concluded that once all the continents were united, but for some reason they have separated to take the current location. Today, it is known that the separation of the continents is due to the spreading of the ocean floor and the movement of tectonic plates.
However, Wegener understood that the alignment of the continents alone did not prove that a supercontinent had existed. So he began looking for additional evidence in 1910 and continued to work on the project until his death in 1930.
Evidence for the theory of continental drift
Geographic evidence of continental drift
Basically, geographic evidence is all that shows that some parts of the continents fit together like a puzzle.
The best example is the geographic fit between Africa and South America.
paleontological evidence (fossils)
In this case, the location of several species of animal and plant fossils that basically they couldn’t fly or swim in order to avoid thinking that because of that they have been able to jump from one continent to another.
Those unique species were found to be found in what is now Antarctica, Africa, Australia, South America, and India. IF they couldn’t fly or swim then how do they appear in different places around the world?
This suggested that instead of migrating by flight or across oceans, those species basically evolved and spread in Pangea, long before the continents drifted apart.
Geological and tectonic evidence
This type of evidence demonstrates through the similarity of rocks and geological structures that appear in different places that the continents were once united in a supercontinent.
A great example is the deformed rocks of the Cape Fold Belt of South Africa which are similar to the deformed rocks found in the province of Buenos Aires in Argentina, if you map Pangea both mountain ranges coincide in space.
Another excellent example is the Appalachian Mountains of North America which disappear abruptly into the coast and coincide with mountain ranges of the same age and with the same geological characteristics in Greenland, Ireland, Norway and Great Britain.
This is practically only explained with the Pangea theory.
Climate evidence of continental drift
Certain types of sedimentary rocks form in specific climatic zones. Glaciers and gravel deposited by glacial ice, for example, form in cold climates and are therefore found at high latitudes and altitudes. The sandstones that preserve desert sand dune structures form where deserts are common, near 30° north and south latitudes. Coral reefs and coal swamps thrive in near-equatorial tropical climates. Therefore, each of these rocks reflects the latitude in which it was formed.
Wegener plotted 250-million-year-old glacial deposits on a map showing the modern distribution of the continents. He notes that glacial deposits would have formed in tropical and subtropical zones.
The same glacial deposits and other climate indicator rocks are shown, plotted on Wegener’s Pangea map. Here, the glaciers cluster neatly around the South Pole. The other rocks are also in logical locations.
Despite all this evidence presented by Alfred Wegener to the scientific and geological community, for those scientists it was not enough because there was no explanation of how it was possible for the enormous continental masses to move along the crust. scientists took the continental drift theory to be incorrect and it was forgotten for more than 30 years. But it was not until many years after Wegener’s death that groundbreaking evidence appeared that would virtually confirm the young scientist’s claims.
No scientist tried to prove Wegener wrong, they just took the theory as wrong and forgot about it……
Evidence for Paleomagnetism and Mid-Ocean Ridges
These evidences basically discovered the following:
Discovery of mid-ocean ridges
First, a large interconnected volcanic mountain belt was discovered in the middle of all the oceans, known as the lava system. mid-oceanic ridges. Studies revealed that this volcanic belt is responsible for forming new ocean floor in the form of basalt.
These ridges are currently known as those responsible for generating new oceanic crust and as divergent tectonic plate boundariesIn addition, they are the geological structures where the expansion of the oceanic floor begins.
The paleomagnetism of the rocks of the ocean floor
Here it was discovered that the basaltic rocks that make up the ocean floor during its formation are magnetized according to the magnetic north at that time on the planet.
However, when analyzing the entire ocean floor, the scientists observed that the magnetism of the rocks was different in several places aligned parallel to the oceanic ridges.
This indicates that the earth’s magnetic north is changing and that the rocks on the ocean floor have not been stable over time.
Age of ocean floor rocks
Geologists discovered that basaltic rocks that are further from the mid-ocean ridges, that is, those close to the continents, are older, denser and colder.
In addition, when measuring the age of the rocks on the ocean floor and comparing them with the rocks of the continents, it is clearly noted that the rocks of the continents are much older than the rocks of the ocean floor.
This clearly explained that the rocks on the ocean floor were constantly being recycled in some way.
This led to the conclusion that there is some mechanism on earth that recycles ocean floor rocks and also creates new rocks through mid-ocean ridges. This gave rise to tectonic plate boundaries, where converging plate boundaries (subduction) are where ocean floor rocks are destroyed, while mid-ocean ridges (divergent boundaries) are where new ocean crust is created. In addition, this mechanism allows the continents to separate because the constant recycling of the oceanic crust pushes the great continental masses, while it expands.
The Final Evidence: The Discovery of the Asthenosphere
Finally, since the 1960s, geophysical studies of the interior of the earth were constant until it was discovered that there is a layer of plastic behavior that is found under the crust and the lithospheric plates, that is, under the rigid lithosphere.
This plastic layer was called asthenosphere, and it is that layer that allows the continents and the rigid lithospheric plates to move as if they were floating, pushed by the processes of subduction and convection that occur in the earth mantle, explaining the Theory of continental drift.