Magellan Rise (ocean plateau)

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Magellan Rise is a huge underwater plateau in the Pacific Ocean, about 500,000 square kilometres in size. There is another feature with the same name west of the Marshall Islands. Scientists think Magellan Rise formed during a time of intense volcanic activity, around 145 million years ago, or between 135 and 128 million years ago. It could have formed where tectonic plates met, or from a mantle plume pushing magma up from deep inside the Earth, possibly connected to the JASON superplume. Possible source plumes include the Easter hotspot and the Foundation hotspot. The total amount of rock it contains is uncertain, perhaps from 1.8 to 19.7 million cubic kilometres. It formed first on the Phoenix Plate and moved to the Pacific Plate about 125 million years ago. Since the Cretaceous, it has stayed buried under deep-sea sediments, from the late Jurassic to today. These sediments include chalk, chert, limestone with fossils such as belemnites, molluscs, and polychaete worms, phosphates, and volcanic ash from the Ontong Java Plateau, laid down during the Selli Event.