Ayooshi Mitra, Amity University Kolkata
Basalt is a fine-grained rock that forms when mafic lava, rich in magnesium and iron, is released at the surface. Basaltic volcanic rock accounts for nearly 90% of all volcanic rock on the planet, and it has resulted in large igneous provinces such as the Deccan Traps (India), Hawaii, and Iceland. It is also common on other planetary bodies such as the moon and Mars. The pressure in the upper mantle of the Earth’s interior causes basaltic magma to develop. The melting point of the mantle is raised as a result of the weight of the overhead rocks, causing the hot deformed rock to move upwards. However, the newly discovered basalt differs from previously known basalts in both chemical and mineral composition.
While drilling through the Pacific Ocean, an international team of researchers discovered a new type of rock on the seafloor. The rock is a type of basalt formed by the rapid cooling of fast-flowing lava containing iron and magnesium. The research team, which included members from Australia, the United States, Japan, Germany, the United Kingdom, Switzerland, and China, drilled 6 kilometers down to the ocean floor of the AmamiSankaku Basin which is in the Japanese Sea, around 1,000 kilometers southwest of Japan’s Mount Fuji volcano. The region is part of the Pacific’s ‘ring of fire’ subduction zone, a 40,000km-long tectonically active zone that hosts several annual volcanic eruptions and earthquake activity. The researchers were looking for basalt from the region’s early eruptions, which occurred nearly 50 million years ago.
The recovered rocks, according to the researchers, were noticeably different from previously known rocks of this type. They may be as dissimilar to known ocean floor basalts on Earth, as Earth’s basalts are to Moon’s basalts. Now that the researchers have determined where and how this rock type is formed, they anticipate that many other rocks previously thought to have been formed by ocean floor eruptions will be re-examined, potentially altering our overall understanding of basalt formation. There haven’t been many rocks like this discovered in millions of years, and this basalt was also buried deep beneath kilometers of sediment at the ocean’s bottom. The eruptions that produced the newly discovered basalt are thought to have happened very quickly, within 1-2 million years, and spanned an area as large as Western Europe. The findings were published in the journal “Nature Communications”.
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Reference:
- Li, H., Arculus, R.J., Ishizuka, O. et al. Basalt derived from highly refractory mantle sources during early Izu-Bonin-Mariana arc development. Nat Commun 12, 1723 (2021). https://doi.org/10.1038/s41467-021-21980-0
- https://theprint.in/science/scientists-discover-new-type-of-basalt-rock-formed-nearly-50-million-years-ago-on-ocean-floor/627573/
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