News

Plate Tectonics started 3 billion years ago

Wed, 21 Mar 2012 13:45:00 GMT

New research shows that plate tectonics started three billion years ago. The Earth’s crust is now undergoing high rates of destruction; this is the major conclusion of research published in the journal Science.

Dr. Craig Storey from the University of Portsmouth’s School of Earth and Environmental Sciences working with academics from the University of Bristol and St Andrew’s University has published a collaborative paper in the journal Science.

The conclusions drawn by the researchers are that up to three billion years ago the Earth formed new crust in a different way to today, with larger net volumes of new crust created. After three billion years the Earth began to regulate the net amount of new crust produced by destroying and recycling existing crust. This was achieved as tectonic plates moved and collided against each other and one plate was forced below the other and deep into the Earth. This process is known as subduction, which also generates new crust in the form of large volumes of magma above the subduction zone and results in chains of volcanoes such as in the present day Andes. This process also destroys existing crust by eroding and transporting older crust back down to within the Earth’s mantle.

The Research carried out modelled the crustal production rates available from a mineral called zircon in sedimentary samples from across the globe. Looking at Hafnium and Oxygen isotopes in the samples, researchers were able to derive the historical behaviour of magma which is involved in the development of the Earth’s crust.

The researchers discovered that continental growth has occurred in two distinct phases. Between four and three billion years ago the earth underwent a sustained period of continental growth compared to what we know it to be today, generating around 3 cubic kilometre of new crust per year. This was followed by a second stage of growth which occurred between three billion years ago and today in which the researchers recorded a drop in new crust generation of over 75%, down to approximately 0.8 cubic kilometres per year.

Dr. Craig Storey from the University’s School of Earth and Environmental Science said, “What's becoming apparent is that there are various lines of evidence pointing to the same conclusion: that some early form of plate tectonics began around three billion years ago. The challenge now is to determine the nature of that form of plate tectonics, how similar was it to what we can observe today?”

You can read the journal entry in full, online at: http://www.sciencemag.org/content/335/6074/1334.abstract