Laccadive-Chagos Ridge

Laccadive-Chagos Ridge
Name	Laccadive-Chagos Ridge
Other names	Laccadive Ridge; Chagos-Laccadive Ridge
Location	Indian Ocean
Coordinates	05°S–10°N, 70°E–80°E
Length km	~2500
Type	submarine ridge, volcanic province
Age	Paleogene–Neogene

Laccadive-Chagos Ridge The Laccadive-Chagos Ridge is a major submarine volcanic ridge in the Indian Ocean extending from the vicinity of the Maldives and Lakshadweep northward toward the Laccadive Sea and southward through the Chagos Archipelago toward the vicinity of the Ninetyeast Ridge. It forms a topographic high that separates portions of the Arabian Sea and the Bay of Bengal from the deeper central Indian Ocean Basin, and it has played a pivotal role in regional plate tectonics, paleogeography, and oceanographic circulation since the Paleogene.

Geography and Extent

The ridge traverses waters adjacent to the Lakshadweep islands, the Maldives, the Chagos Archipelago, and lies to the east of the Laccadive Sea and west of the Andaman Sea, forming a linear feature roughly aligned with the Ninetyeast Ridge and the Carlsberg Ridge. Its northern extent approaches the continental margin off India and the Kerala coast while its southern terminus approaches the Central Indian Ridge and basins near the Seychelles and Mauritius. Seafloor mapping by expeditions from institutions such as the National Institute of Oceanography (India), the Woods Hole Oceanographic Institution, and the National Oceanic and Atmospheric Administration has refined bathymetric detail, showing seamount chains, ridges, and basin-adjacent escarpments.

Geological Origin and Structure

The ridge is interpreted as a volcanic large igneous province linked to hot-spot or plume-related magmatism during the Paleogene–Neogene, contemporaneous with magmatic provinces like the Deccan Traps and the Réunion hotspot track that produced the Ninetyeast Ridge and Mascarene Plateau. Geophysical surveys including seismic reflection and refraction, gravity, and magnetic studies by the Scripps Institution of Oceanography and the Indian Space Research Organisation reveal thickened oceanic crust, basaltic basement highs, and intrusive complexes that contrast with adjacent oceanic crustal thickness measured near the Carlsberg Ridge. Drill cores from the Deep Sea Drilling Project and the Integrated Ocean Drilling Program provide stratigraphic constraints, showing volcanic flows overlain by pelagic sediments.

Tectonic Evolution and Plate Interactions

Tectonic reconstructions link the ridge evolution to movements of the Indian Plate, the Seychelles Microcontinent, and interactions with the Antarctic Plate and Eurasian Plate during the breakup of Gondwana and subsequent northward drift of India. The ridge records episodic magmatism contemporaneous with the emplacement of the Deccan Traps and the separation events that formed the Somali Basin and the Mascarene Basin, as shown in plate models refined by researchers at the British Geological Survey and the Geological Survey of India. Regional stress fields influenced by the Central Indian Ridge spreading center and transform faults contributed to segmentation observed along the ridge.

Volcanism and Seafloor Morphology

Volcanic centers along the ridge include emergent atolls like the Maldives and submerged seamounts forming guyots and cones analogous to features observed in the Hawaiian-Emperor seamount chain. Petrologic studies conducted by teams from the University of Cambridge and the National Centre for Antarctic and Ocean Research show tholeiitic to alkaline basalts, with geochemical signatures linking some flows to plume-derived magmas similar to those of the Réunion hotspot. Morphologically the ridge exhibits linear volcanic edifices, erosional platforms, and coral-capped structures that have been modified by Pleistocene sea-level oscillations documented in work by the International Union for Quaternary Research and paleoceanographers from the Max Planck Institute for Chemistry.

Sedimentation and Oceanographic Processes

Sediment cover on the ridge consists of pelagic ooze, carbonate bioclastic deposits, and turbidites influenced by monsoon-driven currents from the Indian Monsoon system and the Equatorial Current. The ridge affects regional circulation, steering water masses between the Arabian Sea and the Bay of Bengal and modulating nutrient fluxes that scientists from the National Oceanography Centre (UK) and the Scripps Institution of Oceanography have linked to productivity patterns observed by NASA satellite missions. Core records document Paleogene to Neogene biostratigraphy with calcareous nannofossils and foraminifera used by paleontologists at the Smithsonian Institution and the Natural History Museum, London to constrain ages and paleoceanographic events.

Biological and Ecological Significance

Shallow platforms and coral atolls along the ridge support diverse reef ecosystems comparable to those studied in the Great Barrier Reef and the Coral Triangle, hosting reef-building corals, reef fishes, and endemic species cataloged by teams from the International Union for Conservation of Nature and regional marine institutes. Seamounts provide habitat for benthic communities including sponges and cold-water corals similar to those reported in surveys by the Monterey Bay Aquarium Research Institute and the French Research Institute for Exploitation of the Sea. The ridge also intersects migratory routes of cetaceans documented by researchers at the International Whaling Commission and supports fisheries exploited by fleets from India, Sri Lanka, and Mauritius regulated under regional bodies like the Indian Ocean Tuna Commission.

Human Use and Research History

Historical navigation charts from the British Admiralty noted shallow banks and atolls, and colonial-era surveys by the East India Company mapped parts of the ridge; modern systematic investigations have involved the Deep Sea Drilling Project, the Ocean Drilling Program, and national oceanographic institutes including the National Institute of Oceanography (India), the CSIR (India), and international collaborators like the National Oceanography Centre (UK). Contemporary research addresses resource potential, conservation, and geopolitical aspects involving states such as India, the United Kingdom, and Mauritius, with scientific missions conducted by vessels like RRS James Cook and RV Akademik Mstislav Keldysh. The ridge remains a focus for continued multidisciplinary studies integrating geology, oceanography, and biology by consortia including the Intergovernmental Oceanographic Commission and the International Seabed Authority.

Category:Indian Ocean