Continental Drift, Sea Floor Spreading and Plate Tectonics: Important Theories in the Geophysical Phenomenon Leading to the Origin and Development of Major Land Features

Over the last millions of years, geological processes that are still occurring today have sculpted the surface of the Earth. Continental Drift, Sea Floor Spreading, Plate Tectonics – each of these three fundamental theories changed the way we thought about the Earth: its crust, how it moves, how it evolves. Far more than they compete with each other, they compile and organize knowledge, and each theory was built atop the last and thus provided a broad a framework of why major features of earth, like mountains, ocean basins, and continents, formed and evolved the way they did.

Continental Drift Theory

Had Alfred Wegener first proposed the Continental Drift Theory in 1912 The coastlines of certain continents, especially South America and Africa, appeared to match up like pieces of a jigsaw puzzle, Wegener observed. He theorized that all the continents were once fused into one giant supercontinent, which he famously dubbed Pangaea and began to break apart and drift into their present locations around 200 million years ago. Skepticism was initially leveled against Wegener because of the lack of a possible continental mobilizing mechanism.

Key Points:

Pangaea; A supercontinent that existed from the end of the late paleozoic era to the beginning of the mesozoic era.

Fossil Evidence: Fossils were discovered on distant continents, making scientists suggest they had to have been joined together.

Climate Indication: Coal deposits fossil, as well as glacial marks in tropics indicated that this area was part of other climatic areas.

The theory did not explain what forces were moving the continents.

So although the Continental Drift Theory was criticized for it being lack of evidence and a possible mechanism, it was also a basis for future geology theories as well as incentive for scientists to search for more evidence and a possible mechanism for the movement of the continents.

Sea Floor Spreading Theory

In the 1960s, Sea Floor Spreading Theory was proposed by Harry Hess and Robert Dietz. The theory proposed that the ocean floor is continuously created at mid-ocean ridges and then spread out, pushing the continents apart. The ocean floor spreads, then it cools and becomes more dense, and ultimately is pulled back down into the mantle at subduction zones.

Key Points:

Mid-Ocean Ridges: Ridge of a mountain range under the ocean; where new oceanic crust is formed.

Magnetic Anomalies: Symmetrical magnetic stripes on the ocean bottom served as critical evidence for sea floor spreading. These stripes correspond with episodes of magnetic reversal, indicating that new ocean floor is formed in a bilaterally symmetric manner and moves outward from the mid-ocean ridges.

Trenches, Andres, Uplands and Segmentation The flat-slab idea at subduction zones.

Age of Oceanic Crust: The oceanic crust is much younger than continental crust, with its oldest parts being only about 200 million years old, while continental crust is much older.

The theory of Plate Tectonics was validated, Sea Floor Spreading was the process discovered that is the mechanism driving continental drift.

Plate Tectonics Theory

Plate tectonics, the unifying theory of geology that evolved in the 1960s included continental drift and sea floor spreading. In geology, plate tectonic theory is the explanation of the cause of many phenomena on the planet given that Earth’s lithosphere (the rigid outer layer) is broken into a number of giant tectonic plates that move relative to one another. Landforms are created and modified in the three situations where plates separate, converge or slide past each other.

Key Points:

Protosolar Nebula: The massive cloud of dust and gas out of which the solar system formed.

TYPES OF PLATE BOUNDARIES: There are 3 main types of plate boundaries:

Divergent Boundaries: Plates that move away from each other, creating mid-ocean ridges and rift valleys.

Convergent Boundaries — Where plates smash into each other, creating subduction zones, mountain ranges, and volcanic arcs.

Transform Boundaries: When plates move past each other, they can sometimes cause earthquakes and create faults, like California’s San Andreas Fault.

Mantle convection: A mechanism whereby convection currents within the mantle drive the movement of tectonic plates.

Supercontinent Cycle: The cycle of supercontinent formation and breakup (Pangaea being one example) is explained using plate tectonic processes.

Changes in Important Landform Formation and Evolution

Mountains:

Destructive Boundaries: Two continental plates push against each other, leading to compressing and folding of crust — forming mountain ranges. An example of this is the Himalayas, which were formed through the collision of the Indian and Eurasian plates.

Convergent Boundaries (Subduction Zones): A movement that occurs, as a general rule, when an oceanic plate meets a continental surface and is subducted; this interaction can set in motion the destruction of the oceanic portion and possibly the construction of volcanic mountains (like the Andes or the Cascade Range).

Ocean Basins:

One of which is Divergent Boundaries, forming mid-ocean ridges where plates separate and produce new oceanic crust, continuously broadening ocean basins. This is what is making the Atlantic Ocean grow.

And introducing knowledge: Subduction zones — These exist where oceanic crust is being subducted, or pushed beneath, continental crust.

Continents:

Another effect is the widening between the continents (e.g. opening of the rift valley of East Africa and formation of a possible ocean).

Convergent Boundaries: Where tectonic plates collide they form mountain ranges or deep trenches, resulting in large earthquakes and volcanic activity, dramatically altering the landscape.

Volcanoes:

Divergent Boundaries: Mid-ocean ridges are hot spots for volcanic activity as magma makes its way to the surface in areas where the plates are splitting apart.

In convergent boundaries with both oceanic and continental crust, the oceanic plate goes under the continental plate, melting the mantle, resulting in magma that bubbles up through the crust.

Earthquakes:

Transform Boundaries: The movement of plates past one another at transform boundaries can create dramatic seismic activity like that found at the San Andreas Fault.

Discussions :Earthquakes can occur at converging and diverging boundaries of the tectonic plates as well, due to the stress and strain which results in fracture of the rocks.

Conclusion

Continental drift, sea floor spreading, and plate tectonics are all collections of theories that pertain to one another, and they shape the base of modern geologic theory on the mechanics of the interior of the Earth. It combined everything into one theory, explaining the hows and whys of major landform features through Continental Drift, how the landmasses moved, and Sea Floor Sprreading, they found a mechanism that explained how they swept around on the sea floor, to finally help put it together under the plate tectonics revival. These principles work in concert to create a cohesive view of the earth’s crust and the geological processes that have shaped our planet.