Moving continents
Although we feel like we are standing on an unmoving surface, Earth’s tectonic plates are constantly in motion. The speed of movement varies from plate to plate but is roughly the same speed as your fingernails grow (3 - 5 cm/year). Australia is one of the speedier continents, moving north at 7 cm per year. This movement is great enough to require regular updates of GPS coordinates.
Continents move apart at spreading zones like the Australian-Antarctica mid-ocean ridge or the East Africa rift valley. With continents moving on Earth’s sphere, they are eventually going to converge and collide. Continental collisions produce high mountains like the Himalayas. Oceanic convergence produces volcanic island arcs like Japan and Indonesia. When oceanic and continental plates converge, coastal mountain ranges with active volcanoes are produced, like the Cascade Range and the Andes.
Supercontinents
When most of Earth’s continents have come together into a single mass, it is called a supercontinent. In 1915, Alfred Wegener published a book with evidence that Earth’s continents had once been connected in a land mass he called Urkontinent, which we now know as Pangaea. Evidence for Pangaea is easiest to find because it is the most recent supercontinent. Reconstructing older supercontinents is difficult because rocks have been destroyed and continents fragmented many times.
The continents have been torn apart and put back together in different ways. The former supercontinents of Rodinia and Columbia/Nuna show how modern continents have been fragmented and in very different locations over time. (Rodinia (top) by J Goodge 2011, public domain; Columubia/Nuna (bottom) by A DeZotti 2016, Creative Commons 3.0)
In addition to rearranging themselves over time, the amount of continental crust has been steadily increasing on Earth. The first supercontinent, Vaalbara, formed 3.1 billion years ago. It was the smallest supercontinent composed of Western Australia’s Pilbara craton and South Africa’s Kaapvaal craton. Cratons are ancient pieces of stable continental crust they contain some of the world’s oldest rocks.
More continental crust has formed over Earth’s history and each supercontinent is larger than the one before. Thus, Pangea was the largest supercontinent. It broke apart into the continents we recognise today.
Pangaea was the most recent and largest supercontinent. It broke apart to form the modern continents. (Kieff 2009, Creative Commons 3.0)
The next supercontinent
The continents are halfway through a supercontinent cycle and beginning to come together again. India has become part of Asia and Australia is heading north to do the same. The Pacific Ocean is gradually disappearing, and the Atlantic is getting wider. The next supercontinent will form in about 200 million years. Scientists have several models of exactly how the next supercontinent will form and each of these has a different name. The models of Amasia, Pangaea Ultima, Aurica and Novopangaea are summarised in The Conversation.
Novopangaea is one of the possible future supercontinents. (D1221344 2021, Creative Commons 4.0)
Although humans enjoy thinking about future supercontinents, we are not likely to be around in 200 million years. The average lifespan of a species is one million years, so we probably will not learn which group made the best predictions.
Explore
Model the plate tectonic supercycle and have a tasty snack as shown in our video and student activity.
- Learn how the plate tectonic supercycle affects climate and evolution.
- Read about Alfred Wegener and how he put together evidence for Pangea.
- Put together your own supercontinent using evidence like Wegener as shown in this video.
- ESRI tells the story of plate tectonics with videos and text.
- See tectonic movement around Australia over the past 150 million years in this EarthByte video.
- PBS Eons explains how we learned about supercontinents and their movement over time.
- Find out about massive volcanic eruptions that break apart continents and change climate in the AusEarthEd presentation Large Igneous Provinces and Climate with presentation notes and a student handout.
- Read about the seven supercontinents from InterSTEM.
- SciShow discusses the next supercontinent.