Tectonic Plates

Have you ever watched something simmering on the stove? Well you’ll see steam rise, and if you put on a lid it will actually boil over. If you turn the heat down, then the water and the steam heat drops too. This is how tectonic plates work. Read on for more.

What are Tectonic Plates?

Deep beneath the surface of the Earth, heat rises from the core, which is the centre of the Earth, through the mantle, which is the next layer and then it reaches the crust. It comes up slowly, but it actually moves the mantle. The mantle rises beneath the Earth’s crust before it spreads sideways and then cools again. One it’s cooled down it sinks again.

This is a very slow, but constant movement that has broken the lithosphere, which is the hard part of the Earth’s surface which includes the crust and the upper mantle, in loads of places, which then divides the Earth’s crust into tectonic plates.

This happens over millions of years, and it’s called continental drift. In fact the Earth only moves about 15cm a year.

Major and Minor Tectonic Plates

Most of the Earth is covered by seven major plates and another eight or so minor plates. The seven major plates are the African, Antarctic, Eurasian, North American, South American, India-Australian, and the Pacific plates. Some of the minor plates include the Arabian, Caribbean, Nazca, and Scotia plates.

Continents and Oceans

Tectonic plates are nearly 100km thick. Wow, that’s thick; we wouldn’t want to get caught under one of these!

There are actually two main types of tectonic plates, which are oceanic and continental.

  • Oceanic - oceanic plates are made of an oceanic crust called ‘sima’. Sima is made mostly of silicon and magnesium. Ah, so that’s where it gets its name from.
  • Continental - continental plates are made up of a continental crust called ‘sial’. Sial is made up of silicon and aluminium. Yep, understand the name here too!

Plate Boundaries

If you wanted to see the tectonic plates moving, then the best place would be at the boundaries of the plates as this is where they move the most. There are three types of boundaries.

Convergent Boundaries – this boundary is where two tectonic plates push together. Sometimes they’ll get a bit sneaky and one will move under the other. This is called subduction. Now that’s a word to impress your teacher with! Even though the movement is slow, convergent boundaries can be areas where mountains and volcanoes form, and there can also be a lot of earthquake activity.

Divergent Boundaries - a divergent boundary is one where two plates actually get pushed apart. The area on land where the boundary is found is called a rift. New land is created by magma pushing up from the mantle and cooling as it reaches the surface.

Transform Boundaries - a transform boundary is one where two plates slide past each other. They obviously aren’t too keen on meeting up. These places are called faults and you often find a lot of earthquakes in these areas.

Interesting Facts

Did you know that 250 million years ago all the continents were joined together? This made up one massive continent called Pangaea.

  • The Red Sea was formed where the African and Arabian plates pulled apart. Now this is pretty cool, the rift is getting larger and some people say that the Red Sea will one day from an ocean.
  • One of the most famous transform boundaries is the San Andreas Fault in California. This plate is the cause of many, many, many earthquakes! The Mariana Trench is the deepest part of the ocean. It was made by a convergent boundary between the Pacific Plate and the Mariana Plate. The Pacific Plate is moving under the Mariana Plate.
  • Scientists can now track how tectonic plates move using GPS. Good old GPS!
  • The Himalayan Mountains, including Mount Everest, were formed by the convergent boundary of the Indian Plate and the Eurasian Plate.

So, now you should know everything there is to know on Tectonic Plates. It’s pretty interesting don’t you think, these massive plates moving around the Earth?




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