April 12 (UPI) -- Earth's ice ages were born in the tropics.
According to a new study, the planet's periodic cooling is caused by collisions between continental land masses and volcanic arcs in the tropics. These collision uplift rocks that absorb CO2, and as carbon dioxide is pulled from the atmosphere, temperatures drop.
The theory isn't entirely new. Scientists have been studying the link between tectonic activity and global cooling for several years.
In 2017, researchers at the University of California, Santa Barbara proposed that Appalachian mountain-building on the East Coast, some 445 millions years ago, triggered a succession of weathering reactions that pulled CO2 from the air. At the time, the East Coast was located in the tropics.
For the latest study, published this week in the journal Science, the same researchers expanded on their work.
Scientists built a model to simulate the positioning mountain-building events during the last half-billion years on Earth. The analysis showed volcanic arc-continent collisions in the warm, wet tropics preceded all three major ice ages.
"While we thought this process was important, the relationship between such environments in the tropics and glacial climate was clearer than we expected," Nicholas Swanson-Hysell, an assistant professor of earth and planetary sciences at the University of California, Berkeley, said in a news release.
Swanson-Hysell designed the new model with Francis Macdonald, a professor of earth science at UC Santa Barbara.
According to their model and theory, ice ages end as mountain-building slows and the land masses shift out of the tropics. As volcanic out-gassing proceeds, with CO2 sequestration having slowed, the planets slowly warms back up.
Today, the northern edge of Australia's continental landmass is colliding with the Indonesian archipelago. Unfortunately, the CO2-sequestering mechanisms triggered by such a collision play out across massive timescales -- too slowly to reverse human-caused global warming.