The past three leading ice ages which happened over 540 million years ago, were followed by massive tectonic build-up all across the equator. A team of U.S. researchers’ findings were published in the Journal of Science offering new insight into the causes of ice ages that were believed to be related to volcanic eruptions, until now.
A team from the University of California, led by Francis Macdonald, had been looking at the collision of tectonic plates that created the Himalayas. The team discovered that when an oceanic plate pushes against a continental plate, a mountain range of rock is created.
They also discovered the two collisions that created the Himalayas happened in tropical zones near the equator. They found both collisions were immediately followed by global atmospheric cooling.
This led to questioning if the exposure of new rock caused a chemical reaction that led to global cooling? After examining the rate at which the rock from the oceanic plate reacted with carbon dioxide in the atmosphere, it could have removed enough of the greenhouse gas to trigger an ice age.
The team further researched if there were similar patterns in other ice ages. They traced back the cooling events from the last 540 million years and were able to match them to locations of continental collisions. Their findings revealed that before each ice age, there were collisions in the tropics.
More Than One Reason
They believe that the combination of heat and humidity in the tropics aided in spurring a chemical reaction between calcium and magnesium found in rocks and atmospheric carbon dioxide causing gas to be sucked out of the atmosphere. Atmospheric carbon dioxide has a warming effect on the planet, creating a barrier around the Earth.
This prevents heat from escaping back into space which means its removal led to Earth’s temperature dropping. What this means, we are presently living in an ice age that started over 2.5million years ago. We are in an interglacial period in which the earth goes through a warming period with this ice age.
Right now, there is a zone in Indonesia in which two tectonic plates are colliding. It’s believed this could potentially be responsible for our current ice age along with why we have a cool climate along with ice caps.
It’s believed this will end in approximately 10 million years and it is believed the Earth will return to a non-glacial climate. Macdonald said that due to the current movements of the plates, they can project arc-continent collisions and their latitude will become more uncertain the further the projection.
With further studies, the team hopes to clarify records regarding continental collisions and be able to calculate the changes more clearly regarding carbon dioxide concentrations. Their study shows a coincidence but in order to test causality, they need a better understanding of the chemical mass balance.
Macdonald believes what they have gotten from their work is the geography in the tropics which is particularly important for the chemistry of the oceans and setting the global climate condition.
From the Laboratory of Climate and Environmental Sciences in France, William Gray said even though he was not involved in the study, the findings contributed to their understanding of what causes ice ages over a period of time – volcanic eruptions and/or the chemical breakdown of rocks.
He said it has been long debated which side of this balance is more important for driving the variations in CO2 and climate. The results from the study by Macdonald and his colleagues suggest the changes in the level of CO2 removed from the atmosphere by the weathering of rocks could have driven variations in atmospheric CO2 and the climate over the past 500 million years.
This suggests changes in CO2 emissions from volcanoes may only play a minor role.