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NSWEarth and Environmental ScienceQuick questions
Module 6: Hazards
Quick questions on Tsunami hazards: HSC Earth and Environmental Science Module 6
4short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What are causes?Show answer
The most common cause is a large, shallow undersea earthquake at a subduction zone, where the sudden vertical movement of the sea floor lifts the entire water column above it. Other causes include submarine landslides, volcanic eruptions and caldera collapse (such as Krakatoa in 1883), and, rarely, meteorite impacts. The 2004 Indian Ocean and 2011 Tohoku (Japan) tsunamis were both generated by giant subduction-zone earthquakes.
What is propagation across the ocean?Show answer
In the deep ocean a tsunami has a very long wavelength (often over 100 kilometres) but a small height (less than a metre), so ships at sea may not notice it. Because its wavelength is far greater than the ocean depth, it behaves as a shallow-water wave, and its speed depends on water depth: in deep ocean it can travel at the speed of a jet aircraft, around 700 to 800 kilometres per hour. It loses little energy crossing open water, so it can strike coastlines thousands of kilometres from its source.
What is q1?Show answer
Explain why a tsunami that is barely noticeable in the deep ocean can be devastating at the coast. [3 marks]
What is q2?Show answer
Describe two components of a tsunami warning system and the role of each. [4 marks]
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