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Geography • Physical GeographyHard

How do Quaternary glacio-eustatic sea-level fluctuations interact with coastal geomorphology to explain the genesis of the extensive backwater (Kayal) network along the Malabar coast?

A. Holocene marine transgressions flooded deeply incised river valleys cut during lower glacial sea levels, after which longshore drift built barrier sand spits across river mouths, isolating lagoons from the open sea.✓ Correct Answer
B. Tectonic rifting during the late Quaternary created deep linear grabens parallel to the coast that filled with freshwater from inland streams without any marine influence.
C. Widespread aeolian deflation during glacial maxima scooped out extensive shallow depressions behind the coastline, which were subsequently filled by rising groundwater tables.
D. Volcanic explosions along the continental shelf formed massive submerged calderas that trapped coastal seawater behind ring-shaped coral reefs.

💡 Solution & Explanation

The formation of Kerala's backwaters is a classic example of drowned river valleys modified by marine sedimentation. During glacial periods, lower sea levels caused rivers to cut deep valleys into the coastal shelf. As global sea levels rose during the Holocene transgression, these valleys were flooded, and wave-action coupled with longshore currents constructed sand spits across their mouths, creating sheltered lagoons. There was no widespread volcanic caldera formation or aeolian deflation involved in creating this continuous backwater system.

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