Eruptions wiped out ocean life 94 million years ago

University of Alberta scientists contend they have the answer to mass extinction of animals and plants 93 million years ago. The answer, research has uncovered, has been found at the bottom of the sea floor where lava fountains erupted, altering the chemistry of the sea and possibly of the atmosphere. Earth and Atmospheric Science researchers Steven Turgeon and Robert Creaser found specific isotope levels of the element osmium, an indicator of volcanism in seawater, in black shale—rocks containing high amounts of organic matter—drilled off the coast of South America and in the mountains of central Italy.

According to their research, the eruptions preceded the mass extinction by a geological blink of the eye. The event occurred within 23 thousand years and the underwater volcanic eruption had two consequences: first, nutrients were released, which allowed mass feeding and growth of plants and animals. When these organisms died, their decomposition and fall towards the sea floor caused further oxygen depletion, thereby compounding the effects of the volcanic eruption and release of clouds of carbon dioxide in to the oceans and atmosphere. The result was a global oceanic anoxic event, where the ocean is completely depleted of oxygen, Anoxic events—while extremely rare—occur in periods of very warm climate, which means that this research could not only help prove a mass-extinction theory, but also help scientists studying the effects of global warming.

Source: University of Alberta