GEOLOGIC HISTORY OF THE MALDIVES ARCHIPELAGO

The independent Republic of Maldives, an archipelago in the Indian Ocean (Fig. 1) immediately south of India, is the smallest nation in Asia. It is also the lowest-lying country in the world with an average elevation of only 1.5 m (4.5 feet) above sea level. With the polar ice caps of Earth currently in the process of melting, the sea level rising,  thus the future of the Maldives (which is a popular vacation site) is problematic. In 2022 census, there were about 500,000 people living in the Maldives.

Figure 1. Location of the Maldives (north to south) chain of islands.

This island nation is made up of coral islands and sandbanks built on a submerged ridge. The islands represent low-laying coral atolls. An atoll is a roughly circular structure consisting of a coral reef surrounded by deep water of the open ocean. Typically, there are inlets in the reef that allow ocean water to accumulate in a shallow lagoon (10 to 100 m deep) in the center of an atoll. In some cases, the center of the atoll becomes filled with carbonate sand.

The Maldives began forming 68 million years ago as a hotspot, which also produced the Deccan Traps (lava flows) in India. As India moved northward, the hotspot generated an island chain in the Indian Ocean. Today, the islands are located in the central section of the Chagos-Laccadive Ridge/Plateau which extends from north to south, as indicated by the red arrows in Figure 2.

                                                           
         Figure 2. The arrows point to the extent of the island chain

                       (archipelago) that makes up the Maldives.

    

For an informative step-by-step explanation of the formation of the Maldives, I recommend the website: dreamingofmaldives.com. It is a summary of the history of this remarkable chain of reefs: starting with a chain of active volcanoes, then the eruptions stopped, then sea level rose and the volcanoes sank underwater. At the interior of the islands, fringing reefs formed and eventually became barrier reefs. The entire process of atoll formation took about 30 million years.

There are 16 major atolls (and many minor ones) in the Maldives, each consisting of a ring of coral reef around a lagoon. In some cases the lagoons are open (Fig. 3), partially (Fig. 4) or completely filled (Fig. 5) with coral sand.

Figure 3. Example of a flooded atoll in the Maldives (Google Earth image).

Figure 4. Example of a partially flooded atoll in the northern part of the Maldives, with some human occupation (Google Earth image).

Figure 5. Example of a filled atoll in the northern part of the Maldives, with extensive human occupation (Google Earth image).