Panic prevailed among those living near Nainamvalappu beach in Kerala’s Kozhikode as the seawater receded by close to 50 metres on the evening of Saturday, October 29. The phenomenon lasted a few hours. The Kozhikode district administration, however, ruled out a tsunami and said that no warning was issued by the Kerala State Disaster Management Authority.
While the threat of natural disaster was ruled out, district officials warned locals not to venture into the sea bed. However, as many had gathered there, police and fire officials were deployed to disperse the crowd. "The seawater receded around 30 metres in the evening. Later, it gradually receded to around 50-70 metres,” District Collector Narasimhugari TL Reddy told PTI, adding that it was not possible to measure the exact distance at the time as it was dark. According to him, locals say that the phenomenon is not new, and occurs about once a year at various beaches, and the time and distance of the recession varies.
Many other coastal regions in Kerala had witnessed similar phenomena in the past too. Earlier in 2017 in Kappad beach of Kozhikode sea water receded for about five to 10 minutes. The seawater had receded by about 100-200 metres at the time, and the phenomenon lasted only for a few minutes. No tsunami warning was issued then as well.
Though many associate the receding of seawater with tsunamis, experts believe that the phenomenon can also be caused by expansion of the earth. Another possible explanation could be an inverted storm surge, also known as negative surge. “Severe storms can cause dramatic pressure changes. Reduced pressure pushing down on the ocean causes the ocean to expand upwards, resulting in rising water. When pressure increases, sea surface levels can drop, resulting in a negative surge,” says James MacDonald, an environmental biologist. However, he adds that receding seawater is generally treated as a sign of danger, and it is important to exercise caution in such a situation.
With PTI inputs