CURRENT AFFAIRS
CURRENT AFFAIRS
Description
Scientists have recently analyzed ancient rocks and fossils from Mount Ashibetsu in Japan, Uncovered important insights into Ocean Anoxic Event 1a (OAE 1a), which occurred about 119.5 million years ago. This event was marked by a severe oxygen depletion in the oceans, leading to significant extinctions, particularly among plankton.
Causes Of OAE 1a
OAE 1a is believed to have been triggered by large-scale undersea volcanic eruptions. These eruptions released substantial amounts of carbon dioxide (CO2) into the atmosphere, leading to global warming and disrupting the oxygen levels in the oceans. The resulting combination of elevated CO2 and low oxygen created an environment that was hostile to marine life.
Duration And Consequences
The event lasted just over 1.1 million years and is one of the largest ocean anoxic events documented during the Cretaceous Period. Such events often lead to significant biodiversity loss, as evidenced by the sharp decline in plankton populations during OAE 1a.
The idea of ocean anoxic events was first proposed in the 1970s when geologists discovered black, carbon-rich shale deposits. These deposits formed under low-oxygen conditions, where organic matter accumulated without decomposing, providing evidence of environmental stress in ancient times.
Research Approach
To study OAE 1a, researchers focused on volcanic ash layers found on Hokkaido Island, which were deposited over time from ancient volcanic activity. By examining the crystals in these ash layers, scientists were able to date the eruptions and link them to the timing of OAE 1a. They also analyzed carbon and osmium isotopes to gain insights into the changes in the carbon cycle during this period. This research connected findings from Japan with global volcanic activity, showing that the OAE 1a event began with a rapid increase in volcanic CO2 emissions, followed by the burial of excess organic matter. This pattern is consistent with eruptions from the Ontong Java Nui volcanic complex.
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