← All questionsGS1 · 2014 · Geography ·Formation of Indonesian-Philippine Islands
MAINS 2014
GS1
10 marks

Explain the formation of thousands of islands in Indonesian and Philippines archipelagos.

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7 min
150 words
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What the examiner wants

Explain the geological processes that created thousands of islands in Indonesia and the Philippines.

ExplainMake clear how and why it happens: causes, process, and an example for each point.

Demand-wise check

  1. 1Plate subduction: Indo-Australian plate under Eurasian (Sunda arc); Philippine Sea plate interactions create volcanic island arcs and trenches≈30 words
  2. 2Volcanism: chains of stratovolcanoes (Krakatoa, Tambora, Pinatubo)≈30 words
  3. 3Continental islands: Sunda Shelf (Borneo, Sumatra, Java) submerged by sea-level rise after the last Ice Age≈30 words
  4. 4Coral reefs and atolls in warm shallow seas add small islands≈30 words

Open in about 20 words and close in about 20.

Answer plan

Tectonic settingIsland arcs and volcanismDrowned shelfCoral islandsConclusion

Where marks usually go

  • Only 'volcanic origin' and missing Sunda Shelf submergence
  • No diagram of subduction

Draw this

  • Cross-section of subduction zone forming a trench and volcanic island arc

Value addition

  • DataIndonesia has over 17,000 islands; the Philippines counts 7,641 islands (2016 survey).Government surveys
  • ExampleTambora (1815) caused the 'year without a summer' (1816), and Krakatoa (1883) shows the explosive arc volcanism.Volcanological history