This is the first time that the Earth’s geological record—information found inside rocks—has been used to create an animation like this.
Using information from inside rocks on the Earth’s surface, we’ve reconstructed the planet’s plate tectonics over the past 1.8 billion years.
This is the first time the Earth’s geological record has been used in this way, looking back so far into the past. This allowed us to undertake an effort to map the planet for the most recent 40% of its history, which you can see in the animation below.
The work, led by Xianzhi Cao from Ocean University in China, has now been published in the open-access journal Geoscience Frontiers.
A Beautiful Dance
Mapping our planet over its long history creates a beautiful dance of continents—it’s mesmerizing and a natural work of art in itself.
It starts with a map of the world that everyone is familiar with. India then rapidly moved south, followed by parts of Southeast Asia as the former continent of Gondwana formed in the Southern Hemisphere.
About 200 million years ago (Ma or mega-annum in reconstruction), when dinosaurs still walked the earth, Gondwana merged with North America, Europe, and northern Asia to form a large supercontinent called Pangaea.
The reconstruction then continued back in time. Pangaea and Gondwana were formed from collisions of older tectonic plates. Over time, an older supercontinent called Rodinia emerged. The process did not stop there. Rodinia, in turn, was formed by the breakup of an even older supercontinent called Nuna about 1.35 billion years ago.
Why map the Earth’s past?
Of the planets in the Solar System, Earth is the only one with plate tectonics. Its rocky surface is broken into many pieces (tectonic plates) that grind against each other and form mountains, or separate and form deep abysses that are then filled with oceans.
In addition to causing earthquakes and volcanoes, plate tectonics also pushes rocks from deep within the Earth up into mountain ranges. In this way, elements deep underground can be eroded from the rocks and washed into rivers and oceans. From there, organisms can use these elements.
Among these essential elements are phosphorus, which forms the backbone of DNA molecules, and molybdenum, which organisms use to remove nitrogen from the atmosphere and create proteins and amino acids – the building blocks of life.
Plate tectonics also exposes rocks that react with atmospheric carbon dioxide. The rocks that lock up carbon dioxide are key controls on Earth’s climate over long periods of time – much longer than the chaotic climate changes we are responsible for today.
A tool for understanding deep time
Mapping the planet’s past plate tectonics is the first step towards being able to build a complete digital model of Earth throughout its history.
Such a model would allow us to test hypotheses about Earth’s past. For example, why Earth’s climate underwent the extreme fluctuations of a “snowball Earth” or why oxygen accumulated in the atmosphere when it did.
Indeed, this would allow us to understand much more about the feedbacks between Earth’s surface and deep planetary systems that support life as we know it.
Much remains to be learned
Modeling our planet’s past is essential if we want to understand how nutrients became available to drive evolution. The first evidence of complex cells with nuclei—like all animal and plant cells—dates to 1.65 billion years ago.
This is near the beginning of this reconstruction process, and close to the time when the supercontinent Nuna formed. We want to test whether the mountains that grew around the time Nuna formed could have provided the elements that drove the evolution of complex cells.
Much of life on Earth photosynthesizes and releases oxygen. This links plate tectonics to atmospheric chemistry, and some of that oxygen dissolves into the oceans. In turn, some important metals—like copper and cobalt—are more soluble in oxygen-rich waters. Under certain conditions, these metals are then precipitated out of solution: in short, they form ore deposits.
Many metals form in volcanic roots along tectonic plate edges. By reconstructing ancient plate boundaries over time, we can better understand the tectonic geography of the world and help mineral explorers find ancient metal-rich rocks that are now buried beneath much younger mountains.
In an age of exploration of other worlds in the Solar System and beyond, it is worth remembering that there is much about our planet that we are only beginning to understand.
There are 4.6 billion years to study, and the rocks we traverse contain evidence of how the Earth has changed over that time.
This first attempt at mapping 1.8 billion years of Earth history is a step toward the great scientific challenge of mapping our world. But it is just that — a first attempt. The coming years will see significant improvements from the starting point we have taken.
