The heat from radiation processes occurring within the Earth causes the tectonic plates above to shift, gather, or pull apart.
The surface of the Earth is not static. Throughout history, vast landmasses have formed and then disintegrated. Their fragments drift and change from one form to another. Sometimes land is distributed sensibly, but at other times, it all comes together to form massive structures known as supercontinents. Eventually, supercontinents break apart again. So what causes these massive landmasses to form and transform?
Supercontinent Pangea about 200 million years ago. (Photo: Fama Clamosa).
A supercontinent occurs when most or all of the land on the planet comes together to form one large structure. This has happened several times in history, but the most recent example is the supercontinent Pangea. Pangea existed approximately 320 to 195 million years ago, which is not long in the context of Earth’s age. Essentially, Pangea was the only continent on the planet at that time and was surrounded by a single ocean – Panthalassa.
Before Pangea emerged, the Earth also had other supercontinents, including Rodinia (approximately 1.2 billion – 750 million years ago) and Columbia, also known as Nuna (around 1.7 billion – 1.45 billion years ago). There was also Gondwana, a vast landmass that formed about 600 million years ago, but scientists are unsure whether it qualifies as a supercontinent.
No matter how vast and imposing these landmasses were, they could not withstand the chaotic movements within the planet over millions of years. All supercontinents eventually disappeared, and Pangea was no exception. The process causing this change is called continental drift, which relates to the ongoing movement of tectonic plates on Earth.
In fact, the effort to decode the formation and break-up of Pangea led scientists to the plate tectonics theory. This idea was proposed by German meteorologist Alfred Wegener in the early 20th century and was proven correct in the 1960s when technology allowed.
Essentially, plate tectonics theory posits that the outer layer of the Earth – the crust or lithosphere – is made up of multiple plates that move above the mantle. The mantle accounts for about 84% of the volume of the blue planet, lying between the core and the crust. Heat from radiation processes occurring within the Earth causes tectonic plates to move. Sometimes, this movement causes land to come together, forming a supercontinent. At other times, they drift apart, leading to the destruction of the supercontinent.
Pangea broke into many pieces, becoming the continents we see today. This is why the eastern coast of South America fits with the western coast of Africa, resembling pieces of a jigsaw puzzle. These two landmasses were once a united block.
Today, the land on Earth is still moving. On average, they drift about 1.5 cm per year, comparable to the rate at which human toenails grow. However, this rate is not uniform. Areas like the California coastline move faster than average – about 5 cm per year.
When the edges of tectonic plates meet, their movement can cause the crust’s rocks to collide and grind against each other, resulting in earthquakes or volcanic eruptions. This activity can also create new mountain ranges.
Because the process of continental drift is continuous, the current configuration of continents will not last. Experts have observed signs of movement that could lead to a completely different arrangement. For instance, there is evidence that Africa is slowly splitting in two. One day, after millions of years, the continents will come together again to form a new supercontinent, surrounded by a massive single ocean, just as it was during the time of Pangea.
