Rama Setu: SSCP activity may trigger a tsunami, say scientists
Additional observations to scientists’ (Gopalakrishnan, Badrinarayanan, Subramanian) monograph on Geo-environment and geo-tectonic perspectives:
- Similar geological setting on the Sri Lankan side of Rama Sethu/ Adam’s Bridge feature to one inferred from NIOT boreholes.
Sri Lankan side also shows limestones of Miocene era at the bottom, while the top layers consist of several parallel; ledges of conglomerate and sand dunes which are hard at the surface and growing coarse and soft as they descend downwards till resting on a bank of sand. Such conglomerates can not be formed at beach fronts. It is probably represents relics of some man made structure.
- Geology and tectonics of GM area
International Indian Ocean Expedition (IIOE< 1975) and the marine surveys in GM area (Murthy et a. 1994) have indicated a bathymetric trough with a channel like feature between 100om and 3000m depth and a magnetically anomalous body below a water depth of 4km with higher susceptibility. Underwater vents of recent extinct volcanoes and epicenters of earthquakes with 5-7M are also known in this area. Gravity low signatures in GM also correspond to the magnetic anomaly. The orientation of the NNE-SSW to NE-SW trending channel within the BathymetricTrough, magnetic anomaly as well as the line joining the volcanic vents and also the one joining the epicenters of earth tremors roughly coincide with the inferred GM-PS fault in Fig. 8 and 9. It is also significant that the line separating the positive and negative magnetic anomalies as well as the axis of the gravity lows in GM correspond to this fault. The slump structures and the submarine canyon feature reported in this area may also be related to the above fault. This fault defined by neo-tectonic activity, extinct volcanic vents, epicenters of earthquakes, magnetic and gravity anomalies is therefore tectonically very important as it cuts across the RS/AB feature.
- Causes of Tsunanis and vulnerability of GM-PS area to them
Cause of tsunamis is mostly thrust type earthquakes with vertical uplifts in subduction zones and other zones of compression, while along the Sunda (Sumatra) Arc, volcanic eruptions have given rise to large tsunamis. The Carlsberg spreading ridge, the old oceanic ridges like the Chagos Ridge and the 90o E Ridge with normal faulting can also give rise to local tsunamis (Rastogi et al., 2007). The most devastating and strongest tsunami was associated with the eruption of Krakatau in Indonesia in 1883, which had affected the entire Indian Ocean and Pacific Ocean and even the English Channel.
It can be seen from the descriptions and discussions in the preceding para that the PB – GM region is a highly unstable and fragile one with all the local tsunami causing factors such as, active fault zones with neotectonic activity, records of earth quakes with the alignment of the epicenters coinciding with active faults, under-water vents of recent extinct volcanoes, higher heat flow signatures with surface manifestations of thermal waters etc. The region is waiting only for a triggering mechanism to operate for a tsunami to strike. Any activity like SSCP destabilizing the barrier zones of RS/AD and Palk Straight will act as this triggering mechanism.