Hidden Landmass Confirms Gondwana Really Was a Supercontinent

Gondwana, the vast landmass that dominated the Southern Hemisphere some 550 million years ago, was a supercontinent, a new study published today in Science Advances reports. The team, including one of the study's co-authors, found a previously hidden part of the Gondwanan landmass, buried under mountains, showing it was bigger than previously thought.

Gondwana was first identified in 1885 from a plant fossil found in India's Gondwana Province and later found in Australia, Africa, Antarctica and South America. A true supercontinent must cover at least 75% of Earth's continental landmass, but Gondwana's five core fragments — India, South America, Africa, Australia and Antarctica — measured only 64%, and adding land from the Appalachians through Europe to Turkey, Iran and Pakistan fell short.

The finding came from a global dataset of granite samples, analyzed using radioactive-isotope dating to determine rock ages. Himalayan granites formed at different times, yet all derived from one continental block that formed 700-550 million years ago as part of Gondwana. Tracing it, researchers followed Gondwanan fragments from India and Southeast Asia through most of China into Kazakhstan, a region previously thought to be ancient ocean floor.

This buried landmass expands Gondwana's continental share to roughly 80%, confirming it as a supercontinent. Once its fragments came together, a volcanic arc chain formed encircling it, running from Russia through China, Australia, Antarctica and South Africa to the Andes of South America — almost 35,000 km (21,750 miles) long, comparable to today's Pacific Ring of Fire.

This ancient ring of fire released large volumes of volcanic gases, chiefly water vapor and carbon dioxide; present-day Ring of Fire volcanoes emit an estimated 1-4 million tonnes of water vapor and 150-370,000 tonnes of carbon dioxide daily. Over 50 million years, the gas released helped shift Earth's climate from icehouse to greenhouse — a change that may have helped kickstart the Cambrian explosion of life between 550 and 500 million years ago.