An archipelago is a group of islands closely scattered in a body of water. Most archipelagos are made of oceanic islands. This means the islands were formed by volcanoes erupting from the ocean floor. An archipelago made up of oceanic islands is called an island arc.

Indonesia and Philippines constitute two of the five main archipelagos in the world, with Indonesia being the largest archipelagic state in the world, in terms of area and population.

Indonesian Archipelago is made up of approximately 17,500 islands out of which more than 6,000 are populated. It has 60 tiny archipelagos and five core islands. Out of 400, about 150 are active volcanoes.

Geographic Location:

• It falls at the boundary of continental plates.
• Indonesia sits between the world’s most active seismic region, the notorious Pacific Ring of Fire , and the world’s second most active region — the Alpide belt.

Formation:

• Both Indonesian and Philippines archipelagos are a result of a combination of volcanic activity and tectonic plate movement. It is a result of Oceanic-Oceanic Convergent Boundary.
• Both islands have been hotbeds of volcanic and seismic activity due to the convergence of continental plates.
• The islands are initially caused by the volcanoes, and later the shifting of tectonic plates (Eurasian plate, Philippines plate) results in their consolidation as a grouping of small islands in a relatively small area.
• Underwater volcanoes lead to seepage of magma onto the sea, thereby creating rock formation. Continual release of magma causes these rock formations to emerge onto the surface of the sea, thus creating an island.
• The shifting tectonic plates and existence of subduction zone in the area where the Indonesian and Philippines Islands are located causes the formation of an island arc or archipelago.

Importance for India:

• The fact that Indonesia and Philippines Archipelago is in the Pacific Ring of Fire, they are prone to multiple earth-quakes and volcanic eruptions.
• These can in turn trigger Tsunamis which has the potential to affect India’s vast coastline as seen during 2004 Tsunami.
• Further, the presence of Mallaca strait, Sunda strait and other straits in the proximity can affect the sea lanes of communication.
• Air traffic disruption due to eruption of volcanoes is a possibility.

Way Forward:

 Being sandwiched between such seismicity has meant the islands experience some of the strongest earthquakes and most powerful volcanic eruptions known on Earth. Thus, it is important to understand the geology to reduce the destruction to man and material.