Before the world map was created, few questioned the distribution of land and sea on our planet. Interest in the shapes of continents arose after the first world map was drawn. Among the various theories explaining the current distribution of land and sea, the 'Continental Drift Theory' is the most influential and controversial. So, does the Continental Drift Theory hold any validity?
Mercator, a Dutch scholar, created the first world map in the late 16th century by compiling geographical data accumulated over time and based on the Age of Discovery. This provided a more accurate understanding of the Earth's geography, sparking interest in the shapes of continents. In the late 19th century, scientists discovered a type of earthworm known as the 'Lumbricus terrestris,' which was widely distributed across the Eurasian continent and the eastern coast of the Americas but absent in the western part of America. This clearly indicated that the Lumbricus terrestris likely 'migrated' from the Eurasian continent across the Atlantic to the eastern coast of America, leaving many scientists puzzled.
Wegener, a German meteorologist, was hospitalized in 1910 at the age of 30. One day, while lying in bed, he noticed a world map on the wall opposite his bed. Suddenly, he was inspired by the contours of the Atlantic coasts, realizing they fit together remarkably well. He noted that the coastlines of Africa and South America resembled two halves of a torn newspaper, fitting together perfectly. He theorized that America and Africa were once connected, but this thought was fleeting and he did not explore it further.
Recent studies suggest that around 450 million years ago, the African continent was located at the South Pole, covered by thick ice, and gradually drifted northward. During this drift, large ice blocks melted, flattening the rocky terrain of the Sahara and creating long, straight ravines.
In the autumn of 1911, Wegener read a book by Mickelson about the peculiar distribution of the Lumbricus terrestris. This led him to recall the strange phenomenon he had noted over a year earlier: the protruding part of Africa's west coast matched the indent of South America's east coast, suggesting that the continents were once a single landmass that later broke apart and drifted away, forming the current coastlines. If this were true, the earthworm did not cross the ocean. Following this line of thought, he conducted further research. In 1912, Wegener published a paper proposing the 'Continental Drift Theory.' In 1915, he released a groundbreaking book titled 'The Origin of Continents and Oceans,' where he argued that the Earth originally had a single landmass called 'Pangaea,' surrounded by a unified ocean known as 'Panthalassa.' Approximately 200 million years ago, significant changes occurred, causing Pangaea to begin breaking apart. The fragmented continents drifted under the influence of Earth's rotation and gravitational forces, like ships sailing on water. These drifting continents eventually reached their current positions, forming the seven continents and four oceans that define today's world map.
Many were skeptical of the Continental Drift Theory, as they found it hard to believe that massive continents could drift through water. Additionally, due to the limitations of contemporary research, Wegener's theory had many flaws and shortcomings. Tragically, Wegener died during his fourth expedition to Greenland in 1930, leaving the primary advocate of the Continental Drift Theory absent. The theory was almost completely forgotten for a time.
However, as marine geological research advanced and extensive data from paleomagnetism was compiled, Wegener's Continental Drift Theory was revived over 20 years later on new theoretical grounds.
British physicist Blackett, an expert in ancient geomagnetism, found direct evidence for continental drift in 1954. In 1961, British scientist Hess proposed the theory of mantle convection and seafloor spreading based on the discovery of magnetic stripes symmetrically distributed along mid-ocean ridges. He theorized that new crust is formed at the ocean ridges, with material from the mantle continually flowing out through cracks in the ridges and solidifying on either side, causing the ridges to expand outward in a wave-like motion. Hess believed this process of movement is still ongoing.
In 1968, French scientist Le Pichon proposed the plate tectonics theory, which posits that the Earth's crust is composed of about 20 major plates, including the Pacific, Indian, American, Eurasian, African, and Antarctic plates. According to his theory, the crust is constantly changing, with the plates carrying continents in motion throughout geological time. Continents have been 'torn apart' multiple times over the ages, with new oceans forming during these separations, while sometimes continents reattach due to plate collisions, transforming former ocean areas into land and vice versa.
The expansion of mid-ocean ridges also leads to continuous seafloor expansion, successfully explaining the current distribution of land and sea on Earth. The plate tectonics theory represents a new geographical perspective, indicating that continents and oceans are not static but rather undergo processes of division and unification, creation and destruction.
With the accumulation of more observational facts, the Continental Drift Theory was revitalized on new theoretical bases after the 1960s. Today, precise measurements from artificial satellites have confirmed that the Atlantic is expanding at a rate of 1.5 centimeters per year, while the Hawaiian Islands in the Pacific are moving closer to both the South American and North American continents at an average rate of 5.1 centimeters per year, and Australia is separating from the Americas at a rate of 1 centimeter per year. However, this does not mean that the theory has been unconditionally accepted by everyone.
To this day, skepticism remains regarding this theory. Some scientists argue that the premise of the Continental Drift Theory is that the Earth's volume and surface area remain constant, which leads to many unresolved questions regarding crustal movements. They believe similar doubts apply to the plate tectonics theory as well. Nonetheless, Le Pichon's idea that continents were once connected has inspired many researchers, including those who later questioned and opposed his theories.
The debate over the validity of the Continental Drift Theory continues, with many new theories emerging. The truth remains undetermined, but it is certain that as discussions on this issue deepen, humanity's understanding will increasingly approach the facts.
