The landmass that became Antarctica was along the Equator. Throughout Earth’s history, several supercontinents have split up and been back together, like the Backstreet Boys.
Our current seven continents and five oceans are the result of more than 3 billion years of planetary evolution, tectonic plates crossing over the top of the semi-solid mud of the Earth’s core.
But mapping the precise movements of these plates throughout this time is a challenge; existing models are often fragmented, spanning only a few million years, or focus only on continental or oceanic changes, not both.
Now, for the first time, a group of geologists has offered an easily digestible sample of 1 billion years of tectonic plate movement.
Geoscientists at the University of Sydney have spent four years reconstructing how land masses and oceans have changed in the past billions of years. As part of a recent study, they animated these changes in the brief video below.
The animation shows green continents weighing on the oceans, which are represented in white. The Ma at the top of the video is the geological speech of 1 million – so 1,000 Ma is 1 billion years ago. The various colored lines represent different types of boundaries between the tectonic plates: the blue-purple lines represent divergent limits, where the plates separate; red triangles indicate converging boundaries, where the plates move together; and greenish-gray curves show transformation limits, where the plates slide laterally, one after the other.
“These plaques move as fast as nails grow, but when a billion years are condensed in 40 seconds, a mesmerizing dance is revealed,” said Sabin Zahirovic, a geologist at the University of Sydney who is co-author of the new study, in a statement the press.
Building a better model of Earth’s plates
The Earth formed 4.4 billion years ago and then cooled enough to form a solid crust with individual plates about 1.2 billion years after that.
Today, one can imagine the planet as a chocolate truffle – a slimy center housed in a hardened shell. The center consists of a semi-solid mantle 1,800 miles thick that surrounds an overheated core. The top layer – only about 21 miles thick – is the crust, which is broken up into tectonic plates that fit together.
These plates surf the top of the mantle, moving as the hottest and least dense material from the depths of the Earth rises towards the crust and the colder and denser material sinks towards the core.
Geologists can assemble an image of which plates were where they were hundreds of millions of years ago, by analyzing what is known as paleomagnetic data. When the lava at the junction of two tectonic plates cools, part of the resulting rock contains magnetic minerals that align with the directions of the Earth’s magnetic poles at the time the rock has solidified. Even after the plates containing these rocks have moved, researchers can study this magnetic alignment to analyze where on the global map those natural magnets existed in the past.
Using paleomagnetics and current plate tectonic data, the study authors were able to create the most complete map of each plate’s journey from 1 billion years ago to the present.
“Simply put, this complete model will help explain how our home, planet Earth, became habitable for complex creatures,” said Dietmar Müller, co-author of the study, in a press release.
The puzzle of the continents of the Earth has not stopped changing, of course. The Pacific Ocean, for example, is shrinking year by year. The Atlantic, meanwhile, is widening – moving the Americas away from Africa and Europe.
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