Theory Of Plate Tectonics: Plate interactions

Introduction

The theory of plate tectonics was introduced in the 1960s. According to the theory of plate tectonics, Earth has an outer layer, called the lithosphere, which is almost about 60 miles (100kms) thick and overlays a semi-solid molten layer known as the Asthenosphere. The lithosphere is divided into seven large plates of continents and oceans. These plates move correlatively at a rate of 5 to 10 cm converging, diverging, or slipping over each other every year, interacting with their boundaries.

The interaction between these boundaries can be a reason for most of the seismic and volcanic activity on Earth. However, volcanoes and earthquakes can happen in the plate interiors. Plate movements can cause mountains to leap up and continents to  fracture. The continents are rooted in the tectonic plates and go with the current passively, resulting in substantial changes in the Earth’s geography.

What are tectonic plates?

A tectonic plate is an enormous, non-uniformed solid rock, usually composed of continental and oceanic plates. The lithosphere comprises the crust and the top mantle that ranges between 5-100kms in ocean parts and 200km in landform parts, while the Asthenosphere, a semi-solid fluid, lies just below the lithosphere in the zone of Earth’s mantle. 

The theory of plate tectonics was first formulated in 1967. A tectonic plate can be a continental plate and an oceanic plate, which occupies the larger part of the tectonic plate.

The Pacific Plate is the largest oceanic plate, while the Eurasian Plate is a continental tectonic plate.

Alfred Wegener formulated the Theory of Continental Drift, in which he proposed that the seven continents of Earth were once a single supercontinent altogether named Pangea. He suggested that these seven continents (Pangea) broke millions of years ago and moved to their current regions. 

The Major and the Minor Tectonic Plates 

The Earth’s lithosphere is broken into seven major and a few minor tectonic plates.

McKenzie and Parker coined that rotational vectors, described by Euler’s theorem, tell the behaviour of tectonic plates and the formation of ridges, transforming faults and trenches. 

Major Tectonic Plates

The major tectonic plates include Young Fold mountain ridges, transform fault and oceanic trenches.

• The Antarctic and the area surrounding the oceanic plate
• The North American Plate (western Atlantic plate distinct from South American Plate with Caribbean islands)
• The South American Plate (western Atlantic plate distinct from South American Plate with Caribbean islands)
• The Pacific Plate 
• The India-Australia- New Zealand tectonic plate
• The Africa (eastern Atlantic plate)
• Eurasian tectonic plate with adjacent ocean plate

Minor tectonic plates

• Arabian tectonic plate (lies in the Saudi Arabian landform)
• Cocos tectonic plate (lies between Central America and Pacific Plate)
• Nazca tectonic plate (lies in the middle of South America and Pacific Plate)
• Philippine tectonic plate(lies in the Asiatic and Pacific Plate)
• Caroline tectonic plate (lies between Philippine and Indian Plate)
• Fuji tectonic plate (Northeast of Australia)
• Juan De Fuca tectonic plate (Southeast of North American Plate)

What is a tectonic plate boundary

 It is a border between two tectonic plates. The tectonic plates gradually and constantly move in different directions. Some move towards each other, some move apart from each other, while some collide past each other.

Types of Tectonic Boundaries

There are three types of tectonic boundaries-convergent, divergent, and transform faults.

Convergent Boundaries 

Convergent boundaries are formed when tectonic plates collide. They are also known as destructive boundaries. These destructive boundaries are often subduction zones, where the heavier tectonic plate slides under the lighter tectonic plate, forming a deep trench. This subduction converts the dense mantle substance into floating magma which arises through the crust to the Earth’s surface. 

• The Himalayan mountain range is an example of convergent tectonic plate boundaries. About 50 million years ago, India and Asia collided, rising to the Himalayas, the highest mountain on Earth
• Mariana Trench is an example of oceanic-oceanic convergent boundary, the deepest point on Earth

Divergent Boundaries

• Divergent boundaries form when tectonic plates pull apart from each other. They are also known as constructive boundaries
• The Magma from Earth’s mantle rises towards the surface and pulls two or more plates apart. Volcanoes and mountains leap up along the gap
• One of the examples of a divergent tectonic plate boundary is the Mid-Atlantic Ridge, where the American tectonic plates are disassociated from the African tectonic plates and Eurasian tectonic plates
• On terrains, The Great Rift Valley in Africa, where plates are wrenched apart. If it continues to happen, Africa will eventually split from the continent and form a new landmass

Transform Boundaries

The transform boundaries are created as tectonic plates that slip horizontally, but these plates get touched where they collide.

• The plate interaction here happens without creating or destroying the crust
• They don’t result in extravagant rising of the mountains or formation of a new ocean, but they result in earthquakes because of the halting motion
• Such a movement of plates almost destroyed San Francisco in 1901
• Majority of the earthquakes happen in The Rings of Fire (the area around the rim of the Pacific Ocean)

Hotspots

Mostly the volcanic activities happen in or adjacent to the plate boundaries, but sometimes these activities happen between two tectonic plates, called Hotspots.

The hotspots are fixed, unlike the tectonic plates. There are nearly 40 to 50 hotspots all over the world.

Major hotspots are:

• The Afar Hotspot lies under northern Ethiopia
• The Reunion hotspot lies below the Reunion Island in the Indian Ocean

Conclusion

The theory of Plate Tectonics is a theory of Earth Sciences, combining the continental drift theory and seafloor spreading. Ideas concerning plate tectonics have evolved from the 1970s. They are responsible for the structures and the formations on the Earth. Plate tectonics is the most extravagant geodynamic event on Earth, and it is fundamentally related to large scale volcanic activity, sea-land changes and earthquakes.