What is a Plate Tectonics? | Types, Definition, Structure, Function & Facts

What is a Plate Tectonics? | A Land in Motion

Although we think that the earth on Earth is fixed and stable, it turns out that it is constantly in motion. However, this movement is too slow for us to notice, as it only moves 1 to 6 inches per year. It takes millions of years for the earth to move a significant amount.

The Lithosphere

The part of the earth that moves is the surface of the Earth called the lithosphere. The lithosphere is made up of the earth’s crust and part of the upper mantle. The lithosphere moves in large land masses called tectonic plates. Some of these plates are very large and cover entire continents.

Major and Minor Tectonic Plates

Most of the Earth is covered by seven major plates and about eight other sub-plates. The seven major plates include the African, Antarctic, Eurasian, North American, South American, Indo-Australian and Pacific Plates. Some of the sub-plates include the Arabian, Caribbean, Nazca, and Scotian plates.

Continents and Oceans

The tectonic plates are about 62 miles thick. There are two main types of tectonic plates: oceanic and continental.

Oceanic – Oceanic plates are made up of oceanic crust called “sima”. Sima consists mainly of silicon and magnesium (hence its name).

Continental – Continental plates are made up of continental crust called “sial”. Sial is composed mainly of silicon and aluminum.

Plate Boundaries

The displacement of tectonic plates is most evident at the boundary between plates. There are three main types of borders:

Convergent Boundaries – A convergent boundary is where two tectonic plates push against each other. Sometimes one plate moves under another. This is called subduction. Although the motion is slow, the converging boundaries can be geologically active areas such as mountain and volcanic formations. They can also be areas of high seismic activity.

Divergent Boundaries – A divergent boundary is a boundary where two plates are far apart. The land where there is a border is called a rift. The new Earth was formed by magma emerging from the mantle and cooling as it reached the surface.

Transform Boundaries – The transform boundary is where two plates slide past each other. These places are often referred to as faults and can be earthquake-prone areas.

Interesting Facts about Plate Tectonics

A well-known transform boundary is the San Andreas Fault in California. It is the boundary between the North American Plate and the Pacific Plate. This is the cause of many earthquakes in California.

The Mariana Trench is the deepest part of the ocean. It is formed by the convergent boundary between the Pacific Plate and the Mariana Plate.

The Pacific Plate is subducting under the Mariana Plate. Scientists can now track the movements of tectonic plates using GPS.

The Himalayas, including Mount Everest, are formed by the converging boundary of the Indian Plate and the Eurasian Plate.