Ahmedabad: Tiny grains of sand along Gujarat’s coastline have quietly stored evidence of ancient natural disasters.Using a scientific technique known as Optically Stimulated Luminescence (OSL), researchers from MG Science Institute, Ahmedabad, have found indications of at least two major tsunamis that struck the region roughly 1,000 years ago and 6,000 years ago. The study, “Optically stimulated luminescence dating of Holocene tsunami deposits along the Gujarat coast, India,” has been authored by Drasti Gandhi and Paras Solanki and published in the latest issue of Elsevier journal ‘Marine Geology’. The research focuses on testing whether OSL can reliably identify tsunami deposits and accurately determine their age, while also assessing which statistical methods yield the best results. OSL works by determining when mineral grains were last exposed to sunlight. Under normal conditions, sand grains are regularly exposed and “reset.” However, during extreme, high-energy events such as tsunamis, sediments are rapidly displaced and buried, leaving them only partially exposed to light. By collecting these grains and analyzing them in controlled laboratory conditions, researchers can retrieve a timeline of such violent events. Dr Gandhi, a project scientist under the DST-WOSA programme, said the findings successfully validate OSL as a dependable tool for identifying and dating ancient tsunami deposits. This opens new possibilities for reconstructing coastal hazard histories in regions where written or instrumental records are absent. “Gujarat’s coast is one of the most economically active coastlines in India, yet our understanding of tsunami hazard here is far behind what we know about cyclones. Establishing the frequency and reach of past tsunami events is the first step towards building robust early warning systems and designing safer coastal infrastructure,” said Solanki, head of the geology department at the institute.BOX Head: OSL method used for analysisResearchers collected samples from a specific depth from the beaches at Panjor Pir near Koteshwar in Kutch and Nagwa Beach of Diu off the Saurashtra coastUsing the OSL method, the samples were analyzed, which indicated that the high-impact events recorded were 1,000 years ago in Kutch and 6,000 years ago in DiuIn the case of Diu, the event is associated with the Owen Fracture Zone in the Arabian Sea, running from the Gulf of AdenAt Panjor Pir, the date aligns with a major earthquake recorded in 1008 CE, which had a possible origin in the Makran Subduction Zone, located off the coast of Iran and Pakistan
