Over 400 million years ago, an upwelling of hot rock from Earth’s mantle tore apart the crust in Mongolia, creating an ocean that lasted for 115 million years. This geological event could help researchers understand the process of supercontinents breaking apart and coming together, known as Wilson cycles. These processes are slow and progress by less than an inch per year, according to study co-author Daniel Pastor-Galán, a geoscientist at the National Spanish Research Council in Madrid. Understanding these processes is crucial for gaining insights into the earth’s complex mechanisms that are not easily visible.
The researchers conducted fieldwork in northwest Mongolia in 2019, studying volcanic rocks from the Devonian period (419 million to 359 million years ago). During this time, two major continents, Gondwana and Laurentia, existed, along with several microcontinents that would eventually form Asia through a process called accretion. The researchers discovered that between 410 million and 415 million years ago, an ocean called the Mongol-Okhotsk Ocean opened up in the region due to a mantle plume – a stream of hot mantle rock.
Mantle plumes are typically involved in the initial stage of the Wilson cycle, leading to the breakup of continents and the formation of oceans. In this case, the mantle plume tore apart crust that had previously come together through accretion, creating a complex geological scenario. The weak spots between the accreted microcontinents, combined with the plume, facilitated the formation of the Mongol-Okhotsk Ocean. The researchers believe that studying this ancient ocean could provide valuable insights into plate motion and tectonic activity over millions of years.
While the Mongol-Okhotsk Ocean eventually closed in the same location where it opened, this pattern is common in the life cycle of oceans. As continents move over mantle hotspots, they leave behind volcanic rocks with distinct chemistry, allowing researchers to track plate motion. The formation of the Mongol-Okhotsk Ocean is believed to be similar to the ongoing crustal spreading seen in the Red Sea, where the crust is expanding by about 0.4 inches per year. This process could eventually lead to the creation of a new ocean in eastern Africa over tens of millions of years.
Looking ahead, the researchers plan to use their data to create computer models that will enhance our understanding of the complex tectonics of the ancient Devonian ocean. By studying these geological events, scientists hope to gain valuable insights into the earth’s processes and the formation of oceans over millions of years.
