New timeline proposed for plate tectonics

May 11, 2017, Tohoku University
Exposure of kimberlite in Siberia Credit: Vladimir Malkovets

Earth's history should include 'pre-plate tectonic' and 'plate tectonic' phases beginning less than a billion years ago, according to a team of geoscientists in the journal Geology.

Earth formed about 4.6 billion years ago. As the surface cooled, it formed a crust over a molten magma interior. Geoscientists disagree over when began—specifically when the top layer of the crust, the lithosphere, began to slide over the underlying mantle. Estimates range from as early as a few tens of millions of years after the Earth formed, to as late as 750 million years ago.

Part of the debate surrounds how to define plate tectonics. Geologist Tatsuki Tsujimori at Tohoku University and colleagues from Canada and the United States suggest 'true plate tectonics' began only 750 million years ago. They argue plate tectonics should be defined primarily by subduction: when a tectonic plate slides beneath another plate, steeply descending into the mantle below.

The steep angle is key because it takes water and deep into the extremely hot mantle. Released water and carbon dioxide accumulate in the mantle, resulting in volatile pressure increases in the , which are released by exploding through the lithosphere in a pipe.

Proposed timeline for plate tectonics. Credit: Tatsuki Tsujimori

These explosion pipes are called kimberlites, and some contain diamonds. Kimberlites and related igneous rocks are formed only inside old continents such as South Africa, Siberia, and North America. Most kimberlites found today are less than 1 billion years old, suggesting that the accumulation of water and carbon dioxide needed for this kind of eruption, and thus the modern style of subduction, began relatively recently.

This paper stimulated a "Discussion and Reply" in the journal. In their reply, Tsujimori and his colleagues lay out their theory in a graphic that breaks up the Earth's history into five stages, the last of which is plate tectonics. This timeline is different from those developed by many other geologists, who argue that plate tectonics encompasses not just deep subduction, but also shallow subduction and other styles of surface recycling that geoscientists call "stagnant lid tectonics".

Photomicrograph of Siberian kimberlite with diamond-bearing mantle peridotite xenolith. Credit: Tatsuki Tsujimori

Stagnant lid tectonics is proposed for tectonically and magmatically vigorous planets like Venus that do not have plate tectonics. Such a tectonic regime likely occurred early on when Earth was still much hotter and the lithosphere was thinner, so plates were not dense enough to sink deep into the Earth or strong enough to hold together as a plate.

Explore further: Short-term episodicity of Archaean plate tectonics

More information: Title: Kimberlites and the start of plate tectonics, R.J. Stern, M.I. Leybourne, and T. Tsujimori, Geology, DOI: 10.1130/G38024.1

Related Stories

Plate tectonics thanks to plumes?

November 11, 2015

"Knowing what a chicken looks like and what all the chickens before it looked like doesn't help us to understand the egg," says Taras Gerya. The ETH Professor of Geophysics uses this metaphor to address plate tectonics and ...

Earth probably began with a solid shell

February 27, 2017

Today's Earth is a dynamic planet with an outer layer composed of giant plates that grind together, sliding past or dipping beneath one another, giving rise to earthquakes and volcanoes. Others separate at undersea mountain ...

Is there an ocean beneath our feet?

January 27, 2014

( —Scientists at the University of Liverpool have shown that deep sea fault zones could transport much larger amounts of water from the Earth's oceans to the upper mantle than previously thought.

Recommended for you

Archaeologists discover Incan tomb in Peru

February 16, 2019

Peruvian archaeologists discovered an Incan tomb in the north of the country where an elite member of the pre-Columbian empire was buried, one of the investigators announced Friday.

What rising seas mean for local economies

February 15, 2019

Impacts from climate change are not always easy to see. But for many local businesses in coastal communities across the United States, the evidence is right outside their doors—or in their parking lots.

The friendly extortioner takes it all

February 15, 2019

Cooperating with other people makes many things easier. However, competition is also a characteristic aspect of our society. In their struggle for contracts and positions, people have to be more successful than their competitors ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.