Mongolia, a landlocked country in East Asia, was once an ocean formed by the upwelling of boiling rock from Earth’s mantle over 400 million years ago. This ocean existed for 115 million years, offering vital clues for understanding Wilson cycles, the processes through which supercontinents break apart and rejoin.
Daniel Pastor-Galan, a geoscientist at the National Spanish Research Council in Madrid and study co-author, explained, “These are slow and broad-scale processes which move ahead by less than an inch every year.” The study highlights the intricate dynamics between Earth’s mantle and crust, shedding light on processes that are not easily observable.
Researchers were intrigued by volcanic rocks found in northwestern Mongolia, dating back to the Devonian period (419 million to 359 million years ago), known as the “Age of the Fishes.” During this time, two major continents, Laurentia and Gondwana, existed along with microcontinents that eventually formed Asia through a slow process called accretion.
Discovery of the Mongol-Okhotsk Ocean
During fieldwork in northwest Mongolia, researchers discovered the Mongol-Okhotsk Ocean, which opened up between 410 million and 415 million years ago. The chemistry of the volcanic rocks indicated the presence of a mantle plume, a stream of hot and buoyant mantle rock.
“Mantle plumes are usually involved in the first stage of the Wilson cycle: the breakup of continents and opening of the ocean, such as the Atlantic Ocean,” said study lead author Mingshuai Zhu, a professor of geology and geophysics at the Chinese Academy of Sciences. The Mongol-Okhotsk Ocean opened in the same region where Mongolia exists today, reflecting a common pattern in ocean life-cycles.
Pastor-Galan added, “A good thing is that a hotspot is relatively stable so they keep on, for many millions of years, in the same place.”
This groundbreaking discovery not only enriches our understanding of Earth’s geological history but also provides a clearer picture of the dynamic processes shaping our planet.
