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DSE Geog Essay 地理例子 | C1: 2018 Oct Indonesia Earthquake, Tsunami & Volcanic Eruption

  • Time of earthquake: 6:30 pm local time

  • Magnitude: 7.5

  • Mount Soputan --> ash --> 6000 m high

  • Death: at least 1340

Formation process:

  • Indonesia lies along the Pacific Ring of Fire --> with the sinking of convection currents --> compressional force is generated --> Eurasian Plate and Indo-Australian plate move towards each other/ converge/ collide --> Indo-Australian plate sinks beneath the Eurasian Plate as it is denser .

  • [volcanic eruption] --> the edge of the Indo-Australian plate melts into the asthenosphere --> with great magma pressure, cracks develop on the Eurasian Plate --> magma rises up along the cracks --> volcanic eruption/ vulcanicity

  • [earthquake + tsunami] --> tension is built up at the subduction zone --> when the stress is greater than the elastic strength of rocks --> energy is released as seismic waves --> submarine earthquake --> vertical displacement of rocks at the seabed (actually horizontal displacement in the actual case, but scientists cannot actually explain fully how it caused this tsunami yet) --> great sea waves generated --> when the waves approach the near shore where the seafloor rises --> the waves grow taller and hit the shore --> tsunami

Are warning systems effective?

  • The Indonesian government has been blamed and criticized for the country's early warning system for tsunami detection

  • Indonesia’s system, completed in 2008, consists of seismographic sensors, buoys, tidal gauges and GPS --> none of these were able to adequately predict the scale of the tsunami

What went wrong?

  • The western coast of Sulawesi has experienced a tsunami from tremors that fell below the warning threshold.

  • An early standby warning was issued predicting a tsunami of 1.6 to 9.8 feet and telling people to evacuate.

  • In this case, cellphone towers in the area had already been destroyed in the earthquake and people did not receive the text message alerts. There were no sirens along parts of the beach in Palu.


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