Horror of Tsunami
On December 26, 2004, “an earthquake of magnitude 9.3 on the Richter scale” (U.X.L. 571) strikes in the Indian Ocean. A small ripple forms at the epicenter moving out rapidly at anywhere from five hundred to six hundred miles per hour. On the shores, people flocked to the beaches as the water receded back farther than usual at a pace unseen before this occurrence. Within a short time, the water was back, and much more with it, slamming the coast and flooding the land. This tsunami affected lives in seventeen different countries from Indonesia, where over 168,000 people died alone, all the way across the ocean to Kenya in Africa. An estimated 230,000 individuals died due to this tsunami with many missing and even more injured. The death toll from this Boxing Day tsunami is a staggering figure and shows the brutal devastation that these waves can leave in their wake. While earthquakes themselves can be deadly forces, they can cause even more unspeakable damage when they end, especially when they occur on the coast or out at sea. For centuries scientists have constantly been working to find ways to improve prediction methods that could save more lives.
Named “tsunami” by Japanese fishermen, “tsu” meaning harbor and “nami” meaning wave, harbor waves as they were called, are actually not harbor waves at all. These waves that form can be deadlier than their originating cause as they pick up speed and rush across the ocean, ultimately finding their destination along the beaches and coasts of land. Earthquakes, landslides, and volcanoes, as well as meteorites, can all contribute to forming these powerful waves out at sea. A common misconception is that these waves are related to the tide or the wind. In fact, it is far more connected to the Earth itself than the air above it. Deep within the Earth, as faults move and plates spread, sink, and grind against each other, earthquakes are likely to form. These earthquakes in the sea often go unnoticed, but the significant ones can cause massive displacements in the water which is how tsunamis form. The formation can occur two ways. The first type of earthquake causes a vertical fall in the seafloor sucking water down with it because water flows to the lowest point. These fall lines that are formed can be hundreds of miles long and will fill almost instantly. Once it fills, the remaining rushing water is forced back out in what can start as small as a forty-one centimeter ripple that can stretch for many more miles in length. That ripple does not remain a ripple for long. The other form of an earthquake pushes a section of seafloor upward vertically for many feet over hundreds of miles launching the water above it out eventually to flatten itself. Landslides, volcanic eruptions, and meteorites cause them by pushing the water out and away at a fast pace by either a pulse in the ground after the event or a large amount of mass being introduced into the water very quickly. Once the wave begins in each of these scenarios, they are similar from this point until landfall. At the start these little ripples that eventually form the wave move out over deep water, they increase in speed over the deeper water, rushing for possibly thousands of miles at hundreds of miles an hour until it finally reaches shallow water and breaks.
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How it works
When tsunamis strike land, they drag with it a mass of water including that which rushed out at the start of the displacement. With this extra water tsunamis often break on the shore like a normal wave, but the difference is that they never stop. A reverse tide current is formed by the break trying to pull the wave back out, but it is useless and as the wave becomes a constant rush of water, continually steamrolling on a straight path to land finding any low area possible. A break in this way occurs because the wave, that could be thought of like a flood that occurs on water and from this combination of speed and mass the momentum is overwhelming the tide’s abilities. As the water floods in, the water behind it pushes the water in the front along which is why the wave is stronger by many times than the tide. The rapid rush of this wave slows as it nears shore, but its impact is devastating to communities that are unprepared. In the shallow water, the ripple turns slowly into a wall of water which is traveling from thirty to three hundred miles per hour which will slam the beaches. This transformation occurs when the wave condenses in the shallows and vertically grows but horizontally begins to shrink, along with it forming a strong forceful current of its own. This originally small ripple is why most sailors do not see the tsunamis out in the open ocean giving them no warning when they go back to port and see destruction. Onshore, however, today there are often warnings and they need to be listened to.
“It was the first of November 1775. All Saints’ Day dawned crisp and cloudless” (Shardy 3) This was the start of one of the worst days in Portugal’s history. On that day there was a quake that rattled Lisbon, a city that seemed almost blessed, for after, the quake, the day deceivingly had turned around in their favor. Following the earthquake, the Tagus River bay in Lisbon, which is generally fairly deep ranging from sixty to a couple hundred feet in depth, receded exposing amazing treasures that had been sunk in the bay since the golden age of the Portuguese Empire. People naturally flocked to the area collecting the treasures not realizing that their supposed blessing was going to be the end for them. Before people could react, the water from a tsunami came back rapidly, killing thousands on its way back in and up the steeply sloped streets that wound through the city. In the aftermath, only one house in the poorer district stood through it all. This disaster gave the world a new need to understand and predict earthquakes. So scientists set out to work and studied warnings and prevention techniques, bringing the study of seismology to the forefront. Through this tragedy, the world gained a valuable piece of information- if the tide recedes quicker or farther than normal get out of there as quick as possible, especially if you felt an earthquake. Scientists are also monitoring the undersea earthquakes that occur to determine which of those can produce a tsunami. Prevention research is far from perfect as the Japanese learned in 2011 with a seawall that was unfortunately too low. Seawalls can be excellent preventive tools if they are high enough to manage the height of the tsunamis, which is, of course, difficult to predict. Another major prevention method for death and damage is the construction of tall buildings that can withstand the power and currents of these destructive forces. However, it is often only the wealthiest countries that can afford to protect themselves in this way.
“The 28 September 2018 magnitude 7.5 Palu, Indonesia earthquake occurred at 1002 UTC.” (UNESCO) Even today these waves can strike unpredictably and most countries other than Japan are too poor to be able to pay the price tag that is placed on new prevention methods. This is what happened in Palu, where most of the structures that could handle the earthquake were destroyed later by the tsunami. “Most tsunamis are caused by earthquakes on convergent tectonic plate boundaries. According to the Global Historical Tsunami Database, since 1900, over 80% of likely tsunamis were generated by earthquakes.” (NOAA) The Pacific is where this plate action occurs on a large scale. Most Pacific countries have seismographs in as many places as possible and they look for earthquakes that are known to be at the point on the Richter scale where a tsunami is likely to form. Armed with this knowledge of where and when an earthquake or landslide that is powerful enough to occur, people in coastal cities should build up defenses against these waves that are known for destroying entire communities and wiping out towns and destroy the economics in the area for a long time. Repairing these places that have mostly been leveled take tedious work and long periods of time, as well as money for the repairs and attempts at preventative buildings that can protect against future terrors.
Economic devastation is another big problem for the countries affected by tsunamis and can be one of the longer lasting effects from the disaster. When the wave hits the land, the force can destroy not only human life but the life of animals and crops as well. The wave may take out oil tanks leading to oil spills or destroy ports that can provide food and resources for people. And the wave, most likely salt water, can devastate fields by washing away crops or killing them to the root in the salty water potentially causing a food and clean water shortage as well. That is why for many villages or towns, it takes many years for repairs to be made and everyone to get back to normal since most of the area was likely damaged or destroyed.
Tsunamis, known incorrectly as harbor and tidal waves by most, are far more destructive and powerful than either of these waves. Scientists can continue to learn and remain optimistic that there will be a guaranteed way to predict these killer waves in the future. While we may not have prediction and prevention perfected, one can see how much closer humanity is to knowing that answer than when the disaster in Lisbon caused the world to wake up and begin to study this in earnest several hundred years ago. International organizations have been setting seismology stations in high-risk places for years trying to give people a chance by pinpointing the likely epicenter of the disturbance and measuring it to determine if a threat is imminent. Now scientists have the details of how and why these waves occur and are focusing on identifying those forty-one centimeter ripple as possible tsunamis in the making. Even without fully accurate technology, there are ways that civilians can keep safe by recognizing the common signs of a tsunami. With these simple and obvious observations, thousands can be saved by even just one person who speaks up about the possible danger. Cities can now be built to house these new warning systems and be strengthened to withstand the power without issue and with little damage done. Through the work these scientists and engineers are doing, countless lives and communities could potentially be saved.