DSE Geog Essay 地理例子 | C1: Tsunamis

Definition

  • Tsunami: series of massive waves in the water body caused by the displacement of a large volume of water which can be mainly triggered by strong and large-scale submarine earthquakes, volcanic eruptions or coastal landslides


Distribution

  • Commonly found along the coastal areas of the Pacific Ocean, also known as the Circum-Pacific Belt / "Pacific Ring of Fire”, which belongs to a zone of active tectonic movement as it is surrounded by destructive and conservative plate boundary, and there is the presence of hotspots


Examples

1. 2015 Chile Earthquake of magnitude 8.3 which led to tsunami

  • Chile lies on the destructive plate boundary --> sinking of convection currents --> compressional force --> collision of the Nazca Plate and South American Plate --> Nazca Plate sinks beneath the South American Plate as it is denser --> when the pressure is greater than the elastic strength of the rocks --> energy is released in the form of seismic waves --> submarine earthquake --> vertical displacement of rocks at the sea bed --> waves towered up into over 4 metres high --> when the sea waves approach the near shore where the sea floor rises --> sea waves grow taller and hit on the shore --> tsunami

​2. 2016 Kaikoura earthquake of magnitude 7.8 in the South Island of New Zealand 

  • Wave height: 7m (詳細解釋如上, 不過要轉番d plates嘅名)