When an undersea landslide occurs perhaps after a nearby earthquake a large mass of sand, mud and gravel can move down the slope. This movement will draw the water down and may cause a tsunami that will travel across the ocean. There is evidence that the Australian coast may have experienced large tsunami during the past few thousand years.
This evidence is revealed through anomalous sedimentary deposits such as those containing shell or coral or other geomorphic features Dominey Howes, ; Goff and Chauge-Goff, More recently, tsunami continue to be recorded in Australia with most presenting little threat to coastal communities.
The significant tsunamis recorded in recent times have all been recorded at tide gauges around the country with some causing damage in the marine environment. The tsunami hazard faced by Australia ranges from relatively low along the southern coasts of Australia to moderate along the west coast of Western Australia. This area is more susceptible because of its proximity to large subduction zones along the south-coast of Indonesia, which is a region of significant earthquake and volcanic activity.
Several significant tsunami have impacted Australia's north west coast region. The largest run-up measured as elevation about sea level was recorded as 7. The largest reported offshore wave height was six metres near Cape Leveque from the August Sunda tsunami. Dominey-Howes D.
Marine Geology doi Goff, J. Progress in Physical Geography 38 2 : DOI: Geoscience Australia is committed to support Australia's capability to manage the impact of natural hazards, including tsunami. Geoscience Australia:. Geoscience Australia receives real-time data from over 60 seismic stations in Australia and more than international seismic stations.
The seismic information is automatically analysed by Geoscience Australia's seismic monitoring and analysis systems that form part of the 24 hours a day, seven days a week operations centre.
When an earthquake occurs, this system automatically computes preliminary information on the earthquake's origin time time at which the earthquake happened , location, depth and magnitude. The Duty Seismologist assesses this information and then calculates a moment magnitude, Mwp, similar to a Richter magnitude to assist in determining the potential for the earthquake to cause a tsunami. If Duty Seismologist considers that the earthquake has the potential to generate a tsunami that may impact Australia, the seismologist sends the information to the JATWC office in the Bureau of Meteorology in Melbourne via a dedicated data link.
This process is completed within 10 minutes of the earthquake's origin time. These instruments provide real-time sea level observations that can verify whether an earthquake has generated a tsunami and, if so, monitor its path. The devastating Indonesia tsunami and earthquake , which killed , people, brought renewed focus on the hazards of these giant waves.
Understanding future risk requires knowing where tsunamis struck in the past, and how often. As researchers uncover signs of prehistoric tsunamis, the scientists are beginning to link these ocean-wide events with societal shifts. The West's written history and legends clearly illustrate the consequences of tremendous tsunamis in the Mediterranean. A great wave destroyed Minoan culture on the Greek island of Crete in B.
The same tsunami may be responsible for the legend of Atlantis , the. More recently, in , an enormous tsunami destroyed Lisbon, Portugal, Europe's third-largest city at the time. The destruction influenced philosophers and writers from Kant to Voltaire, who references the event in his novel "Candide.
But islands face a much greater threat from tsunamis than coastal communities. After the Lisbon tsunami, the king of Portugal immediately set out to rebuild the city, which was only possible thanks to the presence of untouched inland areas. Geological Survey in Woods Hole, Mass. It's the same kind of thing as during bad hurricanes. It takes a lot longer to recover. Exposed on all sides, islands are simply more likely to be hit by tsunamis. People settle in shallow bays, which are protected from storms but actually magnify the height of incoming tsunami waves.
Food in these societies comes from marine resources, which are destroyed by tsunamis, and croplands that become inundated with saltwater.
Boats are smashed, halting trade and communication. Goff said women, children and the elderly are most likely to die, and in Polynesian culture, elders hold the knowledge needed to build boats, make tools and grow food. The islands of the Pacific are particularly vulnerable. About 85 percent of the world's tsunamis strike in the Pacific Ocean, thanks to its perilous tectonics.
Many tsunamis are too small to notice, but some can have a leading wave as tall as 30 meters or more. As powerful as a wave this size is, however, it's the mass of water behind it that is responsible for most of the physical destruction. The wave crashes against objects near the shore and destroys them, but the water behind it can move much farther inland, lifting buildings off their foundations and creating a swirling pool of debris.
The Centers for Disease Control and Prevention reports that the bulk of deaths that result from a tsunami are drownings, but, due to the destruction of public health and sanitation infrastructure, health conditions deteriorate so badly when the tsunami recedes that many more people die in the days after the event.
Adverse conditions include contaminated water and food supplies, lack of shelter and lack of access for medical personnel. Diseases can spread rapidly, and minor infections can quickly turn into major ones. People who can't leave the area quickly enough can die of exposure if they can't find shelter. A tsunami fills fresh water sources, such as streams, lakes, aquifers and reservoirs with saltwater while also contaminating the soil. Salt inhibits plant growth and can render farmland sterile for several years.
The entire contents of commercial and industrial buildings can be washed out by the mass of water, and as a result, chemicals can get mixed together in dangerous combinations and may be washed out to sea or deposited on the ground. This mix includes raw sewage, which adds to the potential for disease.
The rush of water can also undermine cliffs, hills and raised roadways that don't crumble immediately but become unstable and dangerous.
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