The vast mass of land that became Antarctica once sat on the equator. Over Earth’s history, several supercontinents have broken up and come back together as the Backstreet Boys.
Our current seven continents and five oceans are the result of more than 3 billion years of planetary evolution, the tectonic plates crumbling at the top of the Earth’s heart-shaped semi-hard ooze.
But it is challenging to record the precise movements of these plates over that period; the existing models are often gradual, stretching just a few million years, or focusing on just continental or oceanic changes, not both.
Now, for the first time, a group of geologists have offered an easy-to-digest view at 1 billion years of plate tectonic movement.
The geoscientists, from the University of Sydney, spent four years rebuilding how land and oceans have changed over the past billions of years. As part of a recent study, they animated these changes into the short video below.
The animation shows green continents lying across oceans, represented in white. The Ma is at the top of the geological talk video for 1 million – so 1,000 Ma is 1 billion years ago. The different colored lines represent different types of boundaries between tectonic plates: Blue-purple lines represent different boundaries, where plates separate from each other; red triangles mark homogeneous boundaries, where plates move together; and gray-green loops show transformative boundaries, where plates slide side by side.
“These plates move at the speed of fingerprints, but when billions of years are compressed into 40 seconds, a false dance will appear,” said Sabin Zahirovic, a geologist at the University of Sydney. who co-authored the new study, in a press release.
Building a better model of the Earth’s plates
A map shows what Pangea looked like 200 million years ago, with tectonic plate boundaries in white.
Wikimedia Commons
The Earth formed 4.4 billion years ago, and then cooled down enough to form a hard crust with individual plates about 1.2 billion years later.
Today, one can think of the planet as a chocolate truffle – a viscous center trapped in a hard shell. The center is a 1,800-mile-thick semi-solid suit that surrounds a very hot heart. The highest layer – just about 21 miles thick – is the bark, which is separated into corresponding tectonic plates.
These plates surf at the top of the costume, moving around as a warmer, denser material from the depths of the Earth rises towards the crust, and colder, denser material becomes going down to the heart.
Geologists can build up a picture of the plates where they were hundreds of millions of years ago by analyzing so-called paleomagnetic data. When lava at the junction of two tectonic plates cools, some of the resulting rock contains magnetic minerals that align with the directions of the Earth’s magnetic poles at the time the rock solidified. Even after the plates in which these rocks move, researchers can study magnetic alignment to find out where on the global map these natural magnets previously existed.
Using both paleomagnetics and conventional tectonic plate data, the authors of the study were able to create the most accurate map of the journey of each plate from 1 billion years ago to the present day.
Map of the Atlantic floor.
NASA World Observatory Maps by Joshua Stevens, using data from Sandwell, D. et al. (2014)
“Simply put, this complete model will help explain how our home, planet Earth, came to be inhabited by complex creatures,” Dietmar Müller, co-author of the study, said in the press release.
The Earth’s continental puzzle didn’t stop moving, of course. The Pacific Ocean, for example, is declining year after year. The Atlantic, at the same time, is expanding – pushing America away from Africa and Europe.