Scientists from the University of California have finally figured out why the Earth get Ice Age periods every few million years.

According to researchers, this happens when tropical islands and continents collide with volcanic island arcs. Continents and islands inevitably collide over time because of the Earth's constantly moving tectonic plates.

Earth's Default Climate

Earth's climate is largely decided by the amount of carbon dioxide we have in the atmosphere. Carbon dioxide traps the heat and warms the globe.

These days, the planet's carbon dioxide levels are higher than what Earth experienced in the last three million years, which is due to fossil fuel burning since the Industrial Revolution. Still, Earth experienced way hotter climates in the past, which is actually pretty normal for our planet.

Three-quarters of the last one billion years saw Earth enveloped in a pretty balmy climate. It was so hot that no glaciers existed at the time. However, scientists counted six Ice Ages during the time, with two of them so severe that they turned Earth into a one big snowball.

Frigid Interludes

For long, scientists have been wondering what caused these sudden changes in the Earth's climate millions of years ago. After conducting a study, they've discovered that the Ice Ages were the result of the land masses colliding with volcanic land arcs in the tropics.

This event causes what scientists call "global cooling," triggering a glacial climate with vast ice caps. It's part of the Earth's carbon sequestration program, a balancing act between the carbon dioxide emitted from volcanoes and carbon dioxide consumed through chemical reactions with rocks.

Earth has a long-running carbon sequestration program," says UC Berkeley's Nicholas Swanson-Hysell, an assistant professor of earth and planetary science who designed the study with Francis Macdonald, a professor in the Department of Earth Science at UC Santa Barbara.

"We know that these processes keep Earth's climate in balance, but determining what causes shifts between non-glacial and glacial climates on million-year timescales is a long-standing puzzle."

Carbon Sequestration

Carbon sequestration is the Earth's natural response to balance out the carbon dioxide present in the atmosphere. Over geologic time periods, such collisions will happen again, but it is very slow and the possibility of it happening is still in the next million years or so.

Such a phenomenon is already happening in Indonesia, as parts of the country's archipelago are already pushed upward into the mountains on the northern margin of Australia. Scientists believe that one day, the two land masses will collide, resulting in another Ice Age period.

The study was published on Thursday, April 11, 2019, in the online scientific journal Science, led by Nicholas Swanson-Hysell and his teammates Francis Macdonald, Oliver Jagoutz of MIT, UC Berkeley graduate student Yuem Park and Lorraine Lisiecki of UC Santa Barbara.