Plate Tectonics

The countries of The World weren't always arranged they are now. In fact, evidence strongly suggests that most of the Earth's continents have periodically been joined together in supercontinents. The reason for all this? plate tectonics.

What is plate tectonics?

This is the scientific theory that describes the large scale motion of crustal plates around the surface of the Earth. It allows geologists to find explanations for geological events such as earthquakes and volcanoes, as well as the many other processes that form, transform and destroy rocks.

The Earth's crust and upper part of the mantle are broken into large pieces called tectonic plates. These are constantly moving at a few centimetres each year. Although this doesn't sound like very much, over millions of years the movement allows whole continents to shift thousands of kilometres apart. This process is called continental drift.

The plates move because of convection currents in the Earth's mantle. These are driven by the heat produced by the decay of radioactive elements and heat left over from the formation of the Earth.

Where tectonic plates meet, the Earth's crust becomes unstable as the plates push against each other, or ride under or over each other. Earthquakes and volcanic eruptions happen at the boundaries between plates, and the crust may ‘crumple’ to form mountain ranges. You can see these detailed in more detail in our Geological map.

How has the layout of the planet changed?

Plate tectonics also explains the long-term movement of plates, landmass and even continents. Scientist believe that about 270 million years ago, the world's landmass was grouped in one supercontinent named Pangaea.

Pangaea, from the ancient Greek ‘pan’ (entire) and ‘Gaia’ (Mother Earth). It was the original super-continent which comprised of the continents we know today. This illustration shows how the landmass separated over millions of years, in a cyclical process as old as time itself.

You can also watch this handy YouTube animation:

Who discovered all this?

By all accounts, the idea that the continents move was first suggested by one of our favourite cartographers, Abraham Ortelius who thought that the Americas were "torn away from Europe and Africa...by earthquakes and floods”.

It wasn’t until 1912 when pioneering polar researcher Alfred Wegener put forward his theory of Continental Drift – echoing Ortelius’ assertion that the similarity of coastlines of South America & Africa pointed to them once having been joined.

Wegener’s theory wasn’t widely recognised by the scientific community as it was hard to see what immense forces could move landmasses without breaking the ocean floor. Nevertheless he spent the rest of his life compiling evidence to prove his theory (alas he froze to death in Greenland in 1930 on one such expedition).

It wasn’t until after his death that scientists developed the concept of plate tectonics which built on his research and showed that the outermost shell of Earth is divided into tectonic plates which can move between 0 and 100mm each year.

How does it affects map makers?

Every time we produce a new map, we have to update the information we’re portraying – for example, we must keep abreast of political change such as the split of Sudan into North and South. However, we also need to know if there has been any movement of the Earth's plates.

To make sure our maps are accurate, we work with our wonderful map editor who’s job is a simple one: knowing everything about the world, all of the time.

Luckily the continents don’t move much more, or we’d have to make a lot more maps to keep up!