Continental Drift Theory

Continental Drift Theory – Geography Optional Notes

The Earth is a dynamic and ever-changing planet, with its crustal plates constantly moving and shaping the planet’s surface. One of the most groundbreaking and influential theories in geology is the Continental Drift Theory, which suggests that the Earth’s continents were once a single landmass that eventually separated and drifted apart. This theory revolutionized our understanding of the Earth’s history and helped to explain a wide range of geological phenomena, from the distribution of fossils and rock formations to the formation of mountains and ocean basins. In this blog post, we will explore the Continental Drift Theory in more detail, looking at its origins, evidence supporting the theory, and its impact on our understanding of the Earth’s history and geology.

The continents and ocean basins are considered as the most significant “relief features” of the Earth’s surface, and their origin and evolution are essential to investigate. Various scientists have proposed different concepts, hypotheses, and theories on this subject. However, before examining these theories, it’s important to understand the distinct features of the distribution and arrangement of the continents and ocean basins as they exist currently. The oceans cover about 70.8% of the total surface area of the Earth, while the continents represent the remaining 29.2%. It’s also noteworthy that the distribution of continents and oceans is not uniform across both hemispheres.

The following characteristic features of the distributional pattern of the continents and the ocean basins may be highlighted-

  • The northern hemisphere has an overwhelming dominance of land areas, with more than 75% of the Earth’s total land area situated north of the equator. On the other hand, the southern hemisphere is dominated by water bodies. If we divide the globe into two hemispheres, with the north pole located in the English Channel and the south pole near New Zealand, the northern hemisphere would be classified as the “land hemisphere,” while the southern hemisphere would be the “water hemisphere.” Consequently, the land hemisphere would represent 83% of the Earth’s total land area, while the water hemisphere would account for 90.6% of the planet’s total oceanic areas.
  • Continents are arranged in a rough triangular shape, with most of them having their bases in the north and their apices pointed towards the south. If we consider North and South Americas together, they form an equilateral triangle, with the base along the Arctic Sea and the apex at Cape Horn. If we consider these two continents separately, they also form two distinct triangles. Similarly, Eurasia assumes the shape of a triangle, with the base along the Arctic Sea and the apex near the East Indies. The African triangle has its base towards the north and its apex at the Cape of Good Hope. However, Australia and Antarctica do not follow this pattern.
  • The oceans also exhibit a triangular shape, with their bases situated in the southern hemisphere and their apices in the northern hemisphere. The Atlantic Ocean has a base that extends from Cape Horn to the Cape of Good Hope, with its apex located to the east of Greenland. The Indian Ocean also has a southern base, with its two apices located in the Bay of Bengal and the Arabian Sea. Finally, the apex of the Pacific Ocean is near the Aleutian Islands, while its base is located in the southern hemisphere.
  • The Arctic region surrounding the North Pole is predominantly covered by oceanic water, while the South Pole and surrounding region, specifically the continent of Antarctica, is predominantly land area.
  • The continents and oceans are arranged in an antipodal manner, where more than 95 percent of the total land area is diametrically opposite to water bodies. Only 44.6 percent of the oceans are situated opposite to other oceans, and just 1.4 percent of the total land area is opposite to land area. There are two exceptions to this pattern, which are (i) Patagonia, situated diametrically opposite to a part of north China, and (ii) New Zealand, situated opposite to Portugal and Spain (the Iberian Peninsula).
  • Almost one-third of the Earth’s surface is occupied by the vast Pacific Ocean basin.

To determine the authenticity and validity of any hypothesis or theory related to the origin and evolution of continents and ocean basins, one must consider the distributional pattern of these landmasses and bodies of water. The Pacific Ocean basin, island arcs, and festoons pose challenges for scientists attempting to formulate a theory about the origin of continents and oceans. Lowthian Green proposed the “tetrahedral hypothesis” to address these complex issues. While Lord Kelvin, Sollas, and Love also attempted to explain the origin of continents and ocean basins, their views are not discussed here because they rely on outdated arguments and assumptions. Plate tectonic theory has superseded all previous hypotheses and theories in this field. Therefore, this discussion will focus on the concepts of Lowthian Green, F.B. Taylor, A.G. Wegener.

Tetrahedral Hypothesis

Several scientists have tried to address the issue of how the continents and ocean basins formed by using fundamental principles of geometry. The first attempt in this field was the patagonal dodecahedral hypothesis by Elie de Beaumont, but the most significant of all hypotheses based on geometrical principles is the tetrahedral hypothesis proposed by Lowthian Green. This attractive hypothesis, which gained considerable popularity, is based on the properties of a tetrahedron – a solid shape with four identical plane surfaces, each of which is an equilateral triangle. According to S.W. Wooldridge and R.S. Morgan (1959), Lowthian Green’s hypothesis is particularly noteworthy.

Different geometrical shapes which were used to postulate the hypothesis of the origin of the continents and ocean basins. The last one is a tetrahedron.
Different geometrical shapes which were used to postulate the hypothesis of the origin of the continents and ocean basins. The last one is a tetrahedron.

Origins of the Tetrahedral Hypothesis

After analyzing the distribution of land and water across the world, Lowthian Green put forward his hypothesis. Although it has some limitations and flaws, the tetrahedral hypothesis effectively accounts for the following features of the continents and ocean basins.

  • Dominance of land areas in the northern hemisphere and water areas in the southern hemisphere.
  • Triangular shape of the continents and oceans.
  • Continuous ring of land around north polar sea and location of south pole in land area (Antarctica) surrounded by water from all sides.
  • Antipodal arrangement of the continents and oceans.
  • Largest extent of the Pacific Ocean covering one-third area of the globe.
  • Location of chain of folded mountains around the Pacific Ocean.

In 1875, Lowthian Green proposed a hypothesis that relies on the shared properties of a tetrahedron. His hypothesis is based on two fundamental principles of geometry:

  • Principle 1: A sphere is a body that has the highest volume relative to its surface area.
  • Principle 2: A tetrahedron is a body that has the least volume relative to its surface area.

How the Tetrahedral Hypothesis Explains Earth’s Geography

After conducting several experiments, Lowthian Green concluded that if a sphere was uniformly compressed on all sides, it would transform into a tetrahedral shape.

  • Lowthian Green applied the principle of a sphere transforming into a tetrahedron to the formation of the Earth.
  • He proposed that the Earth was originally a sphere that gradually cooled over time.
  • As the outer layer of the Earth cooled and solidified, a crust was formed.
  • The inner part of the Earth continued to cool and contract, causing a significant reduction in volume.
  • However, the solidified crust prevented further contraction, creating a gap between the upper and inner parts of the Earth.

Flaws in the Tetrahedral Hypothesis

The collapse of the upper part of the Earth onto the inner part ultimately caused the Earth to take on the shape of a tetrahedron. However, Lowthian Green has suggested that the Earth has not yet fully transformed into a tetrahedron but is gradually moving towards that shape as it cools. He has also noted that due to structural variations, the Earth cannot take on the exact shape of a tetrahedron. Therefore, it is natural that there:

  • was a collapse of the upper part onto the inner part.
  • is a gradual process of cooling and movement towards a tetrahedral shape.
  • cannot be a complete tetrahedral shape due to structural variations.
  • In a tetrahedron, a plane face is always opposite to an apex or coign, with the coign being more sharpened in a real tetrahedron.
  • For the Earth, the oceans are the plane faces of the tetrahedron, while the land masses represent the apices or coigns. However, in the case of the Earth, the coigns are not very sharp and are instead flat and convex.
  • Lowthian Green believed that the oceans were formed on the plane faces of the Earth’s tetrahedron, while the coigns became the continents.
Distribution o f land and water on a tetrahedron.
Distribution o f land and water on a tetrahedron.

Evidence of Tetrahedral Hypothesis

The four major oceans – the Pacific, Atlantic, Indian, and Arctic – are believed to have formed on the four plane faces of a tetrahedron-shaped Earth. The plane faces were able to hold water as they were situated lower than the apices or coigns of the tetrahedron. The continents, on the other hand, developed along the apices or coigns of the tetrahedron. This arrangement can be demonstrated by submerging a tetrahedron in water, where the flat surface of the tetrahedron would retain water while the edges or coigns would project above the water.

Lowthian Green proposed that the distribution of the continents and oceans is consistent with a tetrahedral arrangement, with the Earth linked to a tetrahedron standing on one point. The upper flat face represents the Arctic Ocean, while the remaining three faces represent the Pacific, Atlantic, and Indian Oceans. The three vertical meridional edges represent North and South America, Europe and Africa, and Asia, while the lower point represents Antarctica.

The presence of water around the North Pole and the location of the South Pole on a landmass (Antarctica) can be explained by the tetrahedral hypothesis. Three out of the four coigns of the equilateral triangles are located in the northern hemisphere, and they represent the oldest rigid masses around which the present continents have grown. These ancient shields are the Laurentian or Canadian Shield, Baltic Shield, and Siberian Shield. The fourth coign or pivot of the tetrahedron represents the Antarctic shield. The present continents have grown out of these four ancient shields represented by the four coigns of the tetrahedron.

The continents developed along the edges of the tetrahedron tapering southward, which explains the triangular shape of the continents. The location of the oceans along the four plane faces and the continents along the edges or coigns of the plane faces of the tetrahedron supports the antipodal position of land and water.

Gregory acknowledgement

While Gregory acknowledged Lowthian Green’s tetrahedral hypothesis, he proposed some modifications. Gregory suggested that due to the Earth’s shrinkage caused by cooling and contraction, the portion of the vertical tetrahedral edges should remain relatively constant, but the three edges around the polar depression may develop at times in the northern hemisphere and at other times in the southern hemisphere.

Criticism of Tetrahedral Hypothesis

  • The tetrahedral hypothesis explains distributional patterns of continents and ocean basins and their features.
  • However, the hypothesis is not widely accepted due to fundamental defects and errors.
  • It suggests that the balance of the Earth in the form of a tetrahedron while rotating on an apex cannot be maintained.
  • The Earth rotates too rapidly on its axis for it to be converted into a tetrahedron while contracting on cooling.
  • The hypothesis assumes the permanency of continents and ocean basins, whereas the concept of continental drift in the plate tectonic theory suggests otherwise.

Continental Theory of Taylor

Introduction to the Continental Drift Theory of Taylor

In 1908, F.B. Taylor developed his theory of the “horizontal displacement of the continents” with the aim of explaining the puzzling origins of folded mountains during the Tertiary period. Specifically, Taylor sought to address the unique distributional patterns of these mountains, such as the north-south arrangement of the Rockies and Andes along the western margins of North and South America, as well as the west-east extent of the Alpine mountains (including the Alps, Caucasus, and Himalayas).

Reactions to Taylor’s Theory

Despite being unable to find support for his theory from the prevailing “contraction theory,” which failed to explain the distribution of Tertiary folded mountains, Taylor proposed his “drift or displacement theory” as an alternative. While Antonio Snider had presented his own views on “drift” in France as early as 1858, Taylor’s theory is widely regarded as the first attempt to explain the concept of continental drift. Snider’s hypothesis, in contrast, was motivated by the similarities between coal seam fossils from the Carboniferous period found in North America and Europe. Taylor’s work represented an important milestone in the development of the continental drift theory. His proposed mechanism of horizontal displacement helped pave the way for further research in this area, ultimately leading to the development of plate tectonic theory.

Taylor’s Mechanism for Continental Drift

Taylor’s theory of continental drift proposed that during the Cretaceous period, there were two land masses called Lauratia and Gondwanaland situated near the north and south poles respectively. He argued that the continents were primarily composed of sial, which was rare in the oceanic crust. Taylor believed that the continents moved towards the equator, driven mainly by the tidal force of the moon. He also posited that the continents were displaced in two ways: equatorward and westward movements, with both movements being caused by the tidal force of the moon.

  • Lauratia moved radially away from the North Pole towards the equator due to tidal forces of the moon.
  • This movement resulted in tensional forces and caused stretching, splitting, and rupturing in the landmass.
  • Baffin Bay, Labrador Sea, and Davis Strait were formed near the North Pole.
  • Displacement of Gondwanaland from the South Pole towards the equator caused splitting and disruption
  • Formation of several parts, including the Great Australian Bight and Ross Sea around the Antarctic continent
  • Equatorward movement of Lauratia led to the formation of the Arctic Sea between Greenland and Siberia
  • The filling of gaps between the drifting continents with water led to the formation of the Atlantic and Indian oceans.

According to Taylor, the landmasses began to move in lobe form while drifting through zones of lesser resistance, leading to the formation of mountains and island arcs in the frontal part of the moving lobes. The Himalayas, Caucasus, and Alps were formed during the equatorward movement of Lauratia and Gondwanaland from the North and South Poles, respectively, while the Rockies and Andes were formed due to the westward movement of the landmasses.

Criticism Taylor’s Theory

F.B. Taylor’s primary goal was to explain the origin of Tertiary folded mountains, and he suggested that the continents moved at a very large scale to achieve this. However, horizontal movement of the landmasses to a lesser degree would have been sufficient for the formation of mountains. Taylor’s suggestion of landmass displacement of thousands of kilometers was not supported by evidence. Additionally, his proposed mode of drift through tidal forces was considered incorrect. According to A. Holmes, the force responsible for continental drift and mountain formation must come from within the earth rather than external forces.

Conclusion and Significance of Taylor’s Work

Despite the flaws in Taylor’s concept, his hypothesis is considered significant because he vehemently opposed the then-prevalent concept of the permanency of the continents and ocean basins and offered a new direction for solving the problem of their origin. A. Holmes acknowledged Taylor’s contribution by stating that he made an independent and slightly earlier start in this precarious field.

Continental Drift Theory Wegener

Introduction to Alfred Wegener and the Continental Drift Theory

Primarily a meteorologist, Professor Alfred Wegener of Germany introduced his concept of continental drift in 1912. However, it was not until 1922, with the publication of his book “Die Entstehung der Kontinente und Ozeane” (The Origin of Continents and Oceans), which was later translated into English in 1924, that his ideas gained widespread attention. Wegener’s displacement hypothesis drew upon the research and findings of a diverse group of scientists, including geologists, paleoclimatologists, paleontologists, and geophysicists.

Aim of the Wegener’s Theory

Wegener’s main challenge was to explain the significant climatic changes throughout Earth’s history. He recognized ample evidence indicating that the Earth had undergone extensive climate variations in the past. In fact, Wegener’s continental drift theory emerged from the need to explain these major fluctuations in climate.

The climatic changes which have occurred on the globe may be explained in two ways.

  1. Had the continents remained fixed in place throughout the Earth’s geological history, the climate zones would likely have shifted from one region to another over time. Consequently, specific areas would have experienced diverse climatic conditions at different periods.
  2. If the climate zones had remained stable, the land masses could have still drifted and become displaced.

Rejecting the idea of the permanence of continents and ocean basins, Wegener chose the second alternative. Therefore, his displacement hypothesis aimed to explain the worldwide climate changes that had occurred throughout the Earth’s history.

Basic Premise of the Wegener’s Theory

  • Wegener believed in the three-layer system of the earth: outer layer of “sial”, intermediate layer of “sima”, and the lower layer of “nife”.
  • Sial was limited to the continental masses, while the upper part of sima represented the ocean crust.
  • Wegener assumed that all land masses were united in one landmass, named Pangaea, during the Carboniferous period.
  • Several smaller inland seas were scattered over Pangaea, which was surrounded by a huge water body named “Panthalassa,” representing the primordial Pacific Ocean.
  • Laurasia, consisting of present-day North America, Europe, and Asia, formed the northern part of Pangaea, while Gondwanaland, consisting of South America, Africa, Madagascar (now Malagasy), Peninsular India, Australia, and Antarctica, represented the southern part.
  • The South Pole was located near present-day Durban during the Carboniferous period.
  • Wegener’s theory of continental drift begins from the Carboniferous period, and he does not describe the conditions during pre-Carboniferous times.
  • Pangaea was disrupted during subsequent periods, and broken land masses drifted away from each other, leading to the current position of the continents and ocean basins.

Evidences in Support of The Wegener’s Theory

  • Geological evidence
  • Climatic evidence
  • Floral evidence

Wegener used these three types of evidence to support his claim that all landmasses were once united as a single landmass, Pangaea, during the Carboniferous period. The geological evidence includes the matching of rock types, geological structures, and mountain ranges across different continents. The climatic evidence involves the presence of glacial deposits in areas that are now located in tropical regions, suggesting that these areas were once located at higher latitudes. The floral evidence includes the similarity in the distribution of certain plant species across different continents, which suggests that these continents were once connected.

1. Wegener observed a geographical similarity between the coasts on both sides of the Atlantic Ocean. He proposed that the opposing coastlines of the Atlantic could be pieced together like two interlocking pieces of a puzzle, similar to a jig-saw fit.

Jig-saw fitting (juxtaposition) of South America and Africa,
Jig-saw fitting (juxtaposition) of South America and Africa
Jig-saw fitting (juxtaposition) of South America and Africa 2
Jig-saw fitting (juxtaposition) of South America and Africa,

2. The geological evidence suggests that the Caledonian and Hercynian mountain systems found in the western and eastern coastal areas of the Atlantic are identical and similar. The Appalachian Mountains located in the northeastern region of North America are also similar to the mountain systems found in Ireland, Wales, and northwestern Europe.

South America and the western coast of Africa.
South America and the western coast of Africa.
South America and the western coast of Africa 2
South America and the western coast of Africa.

3. In terms of geology, the Atlantic coasts exhibit remarkable similarities. After a thorough examination of the eastern coast of South America and the western coast of Africa, Du Toit concluded that the geological formations of both coasts are largely identical. However, due to the presence of continental shelves and slopes, there exists a gap of 400-800 km between the landmasses of South America and Africa, making it impossible for them to be brought together in close proximity.

4. The fossils and vegetation remains discovered on the eastern coast of South America and the western coast of Africa exhibit a significant resemblance.

5. Based on geodetic evidence, it has been reported that Greenland is moving towards the west at a rate of 20 cm per year. The movement of land masses with respect to each other has been confirmed by evidence of sea floor spreading since 1960.

6. In the northern region of Scandinavia, lemmings, which are small-sized animals, exhibit a peculiar behavior when their population grows significantly. They tend to move towards the west, but unfortunately, they perish in the sea due to the absence of any land beyond the Norwegian coast. This behavior of lemmings provides evidence that land masses were connected in ancient times, and animals used to migrate to far-off places in the westward direction.

7. The presence of glossopteris flora in various regions such as India, South Africa, Australia, Antarctica, Falkland Islands, etc., indicates that these landmasses were once joined together and contiguous in the form of Pangaea.

8. The presence of evidence of Carboniferous glaciation in Brazil, Falkland, South Africa, Peninsular India, Australia, and Antarctica provides further proof that all landmasses were combined into one landmass (Pangaea) during the Carboniferous period.

Continental Drift Theory Distribution of Fossils across the Gondwanaland
Continental Drift Theory Distribution of Fossils across the Gondwanaland

Process of the Wegener’s Theory

As mentioned previously, the primary objective of Wegener in proposing his “drift theory” was to account for significant climate variations documented in the Earth’s geological history, such as the Carboniferous glaciation that covered substantial regions of the Gondwana landmass. In addition, Wegener endeavored to address other geological issues, including the formation of mountains, island arcs, and festoons, as well as the origin and evolution of continents and ocean basins.

Force Responsible for the Drift

  • Wegener believed that after breaking away from Pangaea, continents moved in two directions: equatorward and westward.
  • Equatorward movement of continental blocks was due to gravitational differential force and buoyancy force.
  • Continental blocks were made of lighter sialic materials like silica and aluminum.
  • These blocks floated without friction on denser “sima”.
  • Movement of blocks toward equator depended on relationship between center of gravity and center of buoyancy.
  • Two forces typically act in opposite directions, but due to ellipsoidal shape of Earth, they are related in such a way that if buoyancy point is below center of gravity, resulting force is directed towards the equator.

Wegener attributed the westward movement of continents to the tidal force of the sun and moon. He believed that the attractive force of the sun and moon, which was strongest when the moon was closest to the Earth, pulled the outer sialic crust (continental blocks) over the Earth’s interior and towards the west. However, it should be noted that in any drift theory, the weakest and most challenging aspect is identifying the competent force responsible for the movement of continents. Despite the fact that the tidal force/attractional force of the sun and moon is extremely small, it can still cause movements given enough time.

Actual Drifting of the Continents

  • The disruption, rifting, and drifting of continental blocks began in the Carboniferous period.
  • Wegener referred to the movement of continental blocks away from the poles as “the flight from the poles.”
  • Pangaea was broken into two parts – Lauratia (Angaraland) and Gondwanaland – due to differential gravitational force and the force of buoyancy.
  • The space between these two continental blocks was filled with water, creating the Tethys Sea, during a phase called the “Opening of Tethys.”
  • Gondwanaland was disrupted during the Cretaceous period, causing the Indian Peninsula, Madagascar, Australia, and Antarctica to break away and drift apart due to the tidal force of the sun and moon.
  • North America broke away from Angaraland and drifted westward due to tidal force, while South America broke away from Africa and moved westward due to the same force.
  • The Indian Ocean was formed due to the northward movement of the Indian Peninsula, while the Atlantic Ocean was formed due to the westward movement of the two Americas.
  • The Arctic and North Seas were formed due to the flight of continental blocks from the North Pole.
  • The size of the Panthalassa (primitive Pacific Ocean) was reduced due to the movement of continental blocks towards it from all sides, forming the remaining portion of the Pacific Ocean.
  • Disruption, rifting, and drifting of continental blocks continued from the Carboniferous period to the Pliocene period, resulting in the present arrangement of continents and ocean basins.
Disruption of Pangaea and drifting of continents. The dotted lines denote the present position of continents
and ocean basins.

There have been frequent changes in the positions of the equator and the poles

Shifting of the Position of the Poles
Shifting of the Position of the Poles
  • During the Silurian period, the Equator was located at its most northerly position, passing north of Norway.
  • In the Carboniferous period, it passed through London.
  • During the Tertiary period, it passed through the present locations of the European Alpine mountains.
  • The movement of the South Pole and Equator was obviously in accordance with these changing positions.
  • The prevailing westward and equatorward movements should be understood in reference to these changing positions of the Equator.
Different positions of Poles and Equator
Different positions of Poles and Equator

Mountain Building

  • A.G. Wegener attempted to explain the origin of folded mountains of the Tertiary period with his continental drift theory.
  • The western Cordilleras of North and South Americas were formed when the frontal edges of the westward drifting continental blocks were crumpled and folded against the resistance of the rocks of the sea-floor.
  • The Alpine ranges of Eurasia were folded due to equatorward movement of Eurasia and Africa together with the Peninsula India.
  • Wegener had two different viewpoints regarding the formation of mountains in his theory.
  • According to Wegener, sial (continental blocks) was floating upon sima without any friction and resistance.
  • Later, he pointed out that mountains were formed at the frontal edges of floating and drifting continental blocks (sialic crust) due to friction and resistance offered by sima.
  • The question of how it could be possible remains unanswered.
  • Despite this flaw, S.W. Wooldridge and R.S. Morgan remarked that the hypothesis of continental drift solves more difficulties than it creates in explaining the problem of mountain building.

Origin of Island Arcs

  • Wegener related the origin of island arcs and festoons to differential rates of continental drift.
  • When the Asiatic block (part of Angaraland) moved westward, the eastern margin lagged behind the major landmass, leading to the formation of island arcs and festoons.
  • Examples of these island arcs and festoons include Sakhalin, Kurile, Japan, and the Philippines.
  • Similarly, when some portions of North and South Americas moved westward, they were left behind, resulting in the formation of the island arcs of West Indies and southern Antilles.

Carboniferous Glacitation

  • Glaciation occurred during the Carboniferous period.
  • Brazil, Falkland, Southern Africa, Peninsular India, Australia, Antarctica were extensively glaciated.
  • All continental blocks were united together in the form of Pangaea, according to Wegener.
  • South Pole was located near present-day Durban in Natal.
  • Ice sheets might have spread from the south pole outward during glaciation.
  • Land areas closer to the south pole might have been covered with thick ice sheets.
  • These land areas may have parted away due to the disruption of Pangaea and continental drift.
  • Glossopteris flora may have also been distributed over these areas when they were united together.

Evaluation of the Wegener’s Theory

Wegener’s continental drift theory was a departure from the contemporary orthodox geological ideas of the 19th century, particularly the thermal contraction theory of mountain building. As a result, critics of the contraction theory not only criticized the new theory of horizontal displacement of continents but also discarded it. According to S.W. Wooldridge and R.S. Morgan (1959), Wegener handled his case as an advocate rather than an impartial scientific observer, ignoring evidence unfavorable to his ideas and distorting other evidence to support his theory. Critics of Wegener’s continental drift theory fall into two broad categories: those who searched for errors and discrepancies in Wegener’s original synthesis and those who attempted to modify, enlarge, and correct the original theory while retaining its basic tenet. Different scientists have pointed out various flaws and defects in Wegener’s theory of continental drift.

  1. According to critics, the forces proposed by Wegener (such as differential gravitational force, force of buoyancy, and tidal force of the sun and moon) are insufficient to explain the drifting apart of continents. For instance, the tidal force that Wegener proposed to account for the supposed westerly drift of continents would need to be 10,000 million times stronger than it currently is to produce the required effects. Moreover, such a powerful force would stop the earth’s rotation completely in a year. Similarly, the differential gravitational force and the force of buoyancy cannot adequately explain the equatorward movement of continents. In fact, if the force were so enormous, it might have caused the concentration of continents near the equator instead. These criticisms suggest that Wegener’s proposed forces were not capable of producing the observed effects.
  2. Wegener presented contrasting viewpoints regarding the movement of sialic masses (continents). He initially proposed that the continents were freely floating over the “sima” without any friction. However, later in his theory, he suggested that the “sima” offered forceful resistance to the free movement of the sialic continents, resulting in the formation of mountains along the frontal edges of the floating continents. Nevertheless, the crumpling of sial blocks at their frontal edges to form mountains is difficult to explain, and some experts, such as Wills, argue that compression would not be possible to form the Rockies and the Andes if the “sima” were more rigid than the “sial”. Bowie also maintains that the “sima” lacks the strength to crumple sial and create mountains.
  3. The concept of “juxtaposition” or “jig-saw fit” cannot be confirmed because it is not possible to fully refit both coasts of the Atlantic Ocean.
  4. Wegener did not provide sufficient detail on the chronological sequence or direction of continental displacement. He also did not discuss pre-Carboniferous times, which has led to unanswered questions such as why Pangaea remained intact until its disruption in the Mesozoic era and why the process of continental drift did not begin earlier. Some writers argue that it is unfair to criticize Wegener’s hypothesis based on the absence of pre-Carboniferous mountain building since he did not develop his theory for earlier geological times.

It is evident that Wegener’s theory has had a significant impact on the field of geology. Despite the rejection of many of his ideas, his central concept of horizontal displacement was retained. In fact, the plate tectonic theory, proposed after 1960, is a direct result of Wegener’s continental drift theory. Therefore, Wegener is credited with initiating thought in this field, even if his theories were ultimately proven incorrect. Geologists and others acknowledge that Wegener’s contributions have helped shape our current understanding of world tectonics.

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