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Description
Flashcards by Alice Kimpton, updated more than 1 year ago
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Created by Alice Kimpton
over 7 years ago
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| Question | Answer |
| What is a tsunami? | . A series of very large waves . Created by some sort of undersea disturbances e.g. Earthquake or landslide . The closer they get to land the taller the waves come as land depth is shallower pushing the wave upwards. |
| Where are areas at highest risk? | . West coast of South America . Mexico . West coast of Canada . Alaska . India . Eastern Asia . Indonesia |
| Where are areas at moderate risk? | . Western coast of North America . Australasia . Northern Africa |
| Where are most generated? | Most generated at destructive boundaries when large and shallow earthquakes occur. |
| Why are tsnuamis generated? | Subduction zone related earthquakes generate majority of tsunamis. Usually, it takes an earthquake with a Richter magnitude exceeding 7.5 to produce a destructive tsunami. |
| Where do most tsunamis occur? | About 80% occur in/around Pacific Ocean,but possible wherever there are large bodies of water. |
| What do the waves have? | A series of very large waves with extremely long wavelength- in deep ocean, length from crest to crest may be 100+km (100m for normal wave). |
| What speed can the wave travel away from the source? | The wave could travel away from the triggering source with speeds exceeding 800km/h over very long distances. |
| General wave height | Wave height will usually be around 30cm (2m for normal wave), this is why tsunamis can not be felt abroad ships nor can they be seen from the air in the open ocean. |
| What happens in shallow water? | In shallow waters a large tsunami can crest to heights exceeding 30 metres. Continue at speeds of 60 km/h even when they reach the shoreline. |
| What does a normal sized tsunami look like? | Except for the very largest tsunamis, the approaching wave does not creak but rather appears like a fast moving tidal shore. |
| What may shape a tsunami more? | Open bays and coastlines adjacent to very deep water may shape the tsunami further into a step-like wave with a steep-breaking front. |
| Explain draw back (step one) | If the first part of a tsunami to reach land is a trough (drawback) rather than a wave crest, the water along the shoreline recedes dramatically,exposing normally submerged areas. |
| Explain draw back (step two) | A drawback occurs because the tectonic plate on one side of the fault line sinks suddenly during the earthquake, causing overlaying water to propagate outwards with the trough of the wave at its front. |
| Explain draw back (step three) | There would not be any drawback when tsunami travelling on other side arrives ashore, as the tectonic plate is’ raised’ on that side of the fault line. |
| What is run up? | When tsunami’s wave peak reaches the shore, the resulting temporary rise in sea level is termed run up. A large tsunami may feature multiple waves arriving over a period of hours, with significant time between the wave crests. |
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