TECTONIC PLATES

LITHOSPHERE: Continental Drift & Tectonic Plates

Continental Drift :

As we know, on the Earth where we currently reside, there are seven continents and five oceans. Since we opened our eyes, we’ve been taught this, and even if we look at a world map, it confirms the same. However, if we go back around 280 to 300 million years to the Permian age, it becomes evident that there weren’t originally seven continents and five oceans. Instead, there was a supercontinent and a single ocean.The supercontinent was named Pangaea, and the ocean was called Panthalassa. When it comes to evidence supporting this, research revealed that fossils of certain dinosaurs are found in various continents. Another significant piece of evidence is the symmetry in the coastlines of all continents when closely examined on the world map, clearly indicating that they were once connected as a single entity.

After that, the Triassic age occurred around 210 million years ago. During this period, the supercontinent split into two parts: the northern part named Laurasia and the southern part named Gondwanaland. The sea that separated these two continents was called the Tethys Sea. In the modern era, these continents further divided into the seven continents we recognize today: Asia, Africa, North America, South America, Antarctica, Europe, and Australia. The five oceans are the Pacific Ocean, Atlantic Ocean, Indian Ocean, Antarctic Ocean, and Arctic Ocean.

Lithosphere and Tectonic Plates:

The division of a single continent into seven continents is not a miracle; rather, it is influenced by the Earth’s lithosphere. The lithosphere constitutes the outermost layer of the Earth, formed by the combination of the crust and upper mantle. It is a rigid, solid component of the Earth and represents one of its major domains. The lithosphere is divided into two parts: continental lithosphere and oceanic lithosphere. The continental lithosphere comprises all the land where we reside, including the crust. In contrast, the oceanic lithosphere consists of the crust beneath the oceans and seas, and it is denser than the continental lithosphere. This implies that the lithosphere covers the entire landmass.

In the innermost layers of the Earth, convection currents occur due to extremely high temperatures. These currents lead to the division of the lithosphere into numerous individual plates known as TECTONIC PLATES. The term “tectonic” originates from the Greek word meaning “Builder,” signifying the constructive nature of these processes. These plates tightly fit together, exhibiting various sizes and shapes.

So now, due to the convection currents inside the Earth, these tectonic plates are in continuous motion. These tectonic plates come in two types: Continental Plates and Oceanic Plates.

Continental Plates & Oceanic Plates:

Continental plates are those present on the continental lithosphere. They move at a rate of 2 cm per year. Oceanic plates are located beneath the oceans and seas, continuously moving at a speed of 5 cm per year.

Lithosphere is divided into seven major and minor tectonic plates which are following

Major Tectonic Plates:

  • Pacific Plate
  • North American Plate
  • South American Plate
  • Eurasian Plate
  • African Plate
  • Antarctic Plate
  • Indo-Australian Plate

Minor Tectonic Plates:

  • Cocos plate
  • Nazca plate
  • Arabian plate
  • Philippine plate
  • Caroline plate
  • Fuji plate

So All land and oceans lie on these above major and minor tectonic plates.The average size of these Plates is 100km.

Boundaries of Tectonic Plates:

Now, these tectonic plates are constantly in motion, and the initial concept of continental drift, as mentioned earlier, was also a result of the movement of these tectonic plates. Wherever these plates meet, they have boundaries, also referred to as margins. These boundaries can be classified into three types.

  1. Constructive Boundaries
  2. Destructive Boundaries
  3. Transform Boundaries

Constructive Boundaries:

Tectonic plates move now; when these plates move away from each other, this type of boundary is called a constructive boundary, also known as a divergent margin. When these plates move apart, magma from the Earth’s interior starts to emerge, leading to the formation of volcanoes and mountains.These margins play a crucial role in shaping Earth’s geography. One of the most important geographical features associated with them is the mid-ocean ridge. It forms when underwater land moves away, leading to the emergence of magma and the formation of ridges.

Destructive Boundaries:

In this process, tectonic plates collide; they move towards each other, which is why it’s also called a convergent margin. This movement leads to the formation of deep trenches and mountains. Iconic peaks like Mount Everest are formed due to this margin, underscoring its crucial role in shaping Earth’s topography.

Transform Boundaries:

In this process, tectonic plates move parallelly, sometimes in the same direction and sometimes in opposite directions, which is why it is called a parallel margin. These margins are associated with earthquakes and tsunamis. When Earth’s margins move parallelly, it is responsible for causing earthquakes. This movement doesn’t necessarily lead to the construction or destruction of the crust.

CONCLUSION:

Many people are not initially aware of tectonic plates. When someone first learns that our seven continents were once a single supercontinent and that movements behind these shifts involve the lithosphere, it sparks amazement at how perfectly nature functions. Some might attribute earthquakes solely to the Earth’s movement, but understanding the parallel movements of specific plates reveals a more intricate process.

Explaining volcanic eruptions in detail involves complexities, but grasping the concepts of lithosphere and tectonic plates makes it easier for humans to comprehend how volcanoes occur. The movements of these plates have not only shaped our current continents and oceans but will likely lead to future changes in our world map.

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