Discovered under China! 800 million years old, 640 kilometers long...

This chain of fossil volcanoes, approximately 640 kilometers long and buried beneath China's Sichuan Basin, formed during the early Neoproterozoic era when oceanic crust subducted beneath continental crust. The resulting magma reached the surface, forming a long, narrow chain of volcanoes.

HOW ARE VOLCANIC SPRINGS FORMED?

During subduction, oceanic crust heats up, releasing water, and this causes magma to form. The magma rises to the surface, creating arcs of volcanoes along the plate boundaries. These structures allow new crust to form and old crust to reform.

A research team led by Zhidong Gu and Junyong Li used air-based magnetic sensors to investigate whether previously known volcanic formations extend deep into the Sichuan Basin. These sensors detected iron-rich volcanic rocks. The resulting data revealed a 700-kilometer-long and 50-kilometer-wide belt approximately 6 kilometers below the surface.

EVIDENCE COMES FROM MAGMA

Researchers examined rock samples obtained from deep boreholes in the region. They confirmed that these samples were of magmatic origin and chemically similar to recent crust formed by arc volcanoes. The rocks were estimated to be between 770 and 820 million years old.

This volcanic arc differs from arcs typically formed in narrow areas near continental margins. The researchers suggested that this difference may be due to a specific tectonic process called flat-slab subduction. In this process, the oceanic plate subducts beneath the continental plate at a shallow angle, moving horizontally for hundreds of kilometers before plunging into the Earth's crust. A similar structure is seen today in the Andes Mountains of South America.

THERE MAY BE TWO DIFFERENT SYSTEMS

Geoscientist Peter Cawood of Monash University in Australia suggested that the two volcanic belts may have been separate systems and merged over time. However, he acknowledged that the new data suggests that magmatic activity in the region is much greater than previously thought.

The impact of volcanoes on climate is not overlooked. Volcanic activity releases carbon into the atmosphere, while chemical weathering in mountains absorbs this carbon. These processes play a crucial role in balancing the Earth's carbon cycle and climate for millions of years.