Megaplumes

What is a megaplume? Well a mega plume is a plume. In it’s geological sense, plume is defined as “an up welling of molten material from the earths mantel. The term can also be used to describe a column of hot water ascending from the ocean floor, and a megaplume is an exceptionally large pocket of unusually hot ocean water. The first megaplume was discovered in 1986 on the Juan De Fucaridge, which runs roughly parallel to the Coast of the United States Pacific Northwest, about 300 miles west of Oregon. The unique thing about megaplumes is that it can transport both minerals and animals life to areas far outside the range where they would normally be found, giving researchers no end of unusual things to study. Megaplumes like the one found in the Indian Ocean are probably caused by undersea volcanic eruptions, though scientists aren’t yet certain. Once they are formed they can hang around for years. The heat from such events could have a dramatic effect on ocean circulation, which plays a role in determining Earth’s climate. The energy content is an order of magnitude greater {than ordinary plumes}, and the thermal power may be many orders of magnitude greater. One of the places where there was a megaplume would be in the Indian Ocean and in mid oceans. Megaplumes like the one found in the Indian Ocean are probably caused by undersea volcanic eruptions, though scientists aren’t yet certain. But even the Indian Ocean megaplume may be small compared to larger underwater eruptions that have as yet gone undetected. The new data on hydrothermal fields and megaplumes underscores the fact that volcanic activity on the ocean floor remains a largely mysterious phenomenon.


During an underwater eruption, boiling water sometimes emerges from the ocean floor and expands until it forms a disk ten miles wide or more. At the same time, it begins to rotate and drift away, traveling for months and possibly hundreds of miles. Plates of crust spread away from mid ocean ridges. At some points, the ridges pass over columns of magma rising from deep within the planet. As a result, giant chambers of molten rock form close to the seafloor under the ridges. A sudden surge into the chamber can destabilize it and send up a pipe of molten rock. The heat of this pipe quickly boils seawater and in some cases produces a megaplume. Megaplumes form along mid ocean ridges where tectonic plates pull apart and magma rises toward the seafloor. Because the Juan de Fuca Ridge is only 300 miles off the coast of the Northwestern United States, it is easily studied. In 1986 scientist detected a megaplume for the first time over the Cleft segment of the ridge. Since then megaplumes have been studied over the Gorda Ridge and most recently over a volcano called Axial.