A possible submarine volcano near the central part of Ninety-East Ridge, Indian ocean |
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| Authors: | P Hdervari |
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| Institution: | P. Hédervari |
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| Abstract: | Floating pumice masses have been observed several times near the central part of Ninety-East Ridge, Indian Ocean, in 1879 and in 1883. The author is of the opinion that the source of these pumice masses cannot have been the volcano Krakatau in the Sunda Strait - as has been suggested earlier by other authors -, but that they originated in situ. Examples of floating pumice observed over submarine volcanoes lying at depths of 1500 m or even more, are mentioned briefly by other authors, suggesting that eruptions in deep water may indeed lead to its formation.The suspected submarine volcano may coincide with an elongated but rather flat elevation a little north of the central part of Ninety-East Ridge. The center of this elevation is located approximately at 6° 05′ S, 89° 10 E. A roughly NW-SE profile of this area shows the presence of this shield-like feature very near the site where floating pumice was seen on three occasions. The inferred submarine volcanic center is lying within the belt of heat flow anomaly (called belt I). A particular “hot spot” with an unusually high heat flow value (7.61 HFU) is located southeast of the feature in question. The heat flow values measured in belt I are well above the world-average. This belt may be the result of the presence of linearly arranged magma chambers at a relatively shallow depth, probably within the oceanic crust. This belt has a length of 1100 km.The seismic activity of the area investigated is similarly remarkable. Numerous powerful shocks have taken place there. Belt I represents the axis of the seismic zone, extending from points b to c (Fig. 5). The seismic belt is regarded as a zone of weakness within which fractures can originate, permitting rock-melts to emerge from depth towards the surface. |
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