A team of geologists at the University of Texas at Dallas and Austin has put forward an intriguing new hypothesis that links the dawn of plate tectonics with ‘Snowball Earth,’ a period of climate change that sent our planet into a deep freeze that lasted millions of years. Scientists usually place the start of plate tectonics at about 3 billion years ago, while the new hypothesis, described in the journal Terra Nova, puts the process in a much younger era known as the Neoproterozoic, which occurred about 542 million to one billion years ago.
An artist’s impression of a ‘Snowball Earth.’ Image credit: NASA.
The Earth is the only planet known to have plate tectonics, with its crust and upper mantle being made up of distinct pieces that move slowly and independently, creating and destroying landforms and producing volcanoes and large earthquakes.
Plate tectonics is one of the most fundamental processes that shape the planet, and most researchers believe it has been active for most of the planet’s 4.5 billion-year history.
However, according to the team, there are a variety of traces in the geologic record that could be consistent with plate tectonics not getting started until the Neoproterozoic.
“Earth is the only body in our Solar System known to currently have plate tectonics, where the lithosphere is fragmented like puzzle pieces that move independently,” said team member Professor Robert Stern, from the University of Texas at Dallas.
“It is much more common for planets to have an outer solid shell that is not fragmented, which is known as ‘single lid tectonics’.”
In the study, Professor Stern and his colleague, Dr. Nathaniel Miller of the University of Texas at Austin, suggest that the onset of plate tectonics likely initiated the changes on Earth’s surface that led to ‘Snowball Earth.’
They argue that plate tectonics is the event that can explain 22 theories that other scientists have advanced as triggers of the Neoproterozoic Snowball Earth.
“We went through the literature and examined all the mechanisms that have been put forward for Snowball Earth,” Professor Stern said.
“The start of plate tectonics could be responsible for each of these explanations.”
The onset of plate tectonics should have disturbed the oceans and the atmosphere by redistributing continents, increasing explosive arc volcanism and stimulating mantle plumes.
“The fact that strong climate and oceanographic effects are observed in the Neoproterozoic time is a powerful supporting argument that this is indeed the time of the transition from single lid to plate tectonics. It’s an argument that, to our knowledge, hasn’t yet been considered,” Professor Stern explained.
“In the present day, climate is in the news because we’re changing it by putting more carbon dioxide into the atmosphere.”
“But imagine a time when Earth didn’t have plate tectonics, and it then evolved to have plate tectonics — that would have been a major shift in the Earth’s operating system, and it would have had a huge effect on climate, too.”
_____
Robert J. Stern & Nathan R. Miller. Did the transition to plate tectonics cause Neoproterozoic Snowball Earth? Terra Nova, published online December 20, 2017; doi: 10.1111/ter.12321
