We use the word wave in everyday conversation to refer to ocean, light, sound, or earthquake waves. But what do all of these seemingly different phenomena have in common, and why is it important to understand the nature of waves? Let's explore these topics.
Waves transmit the energy that topples buildings during an earthquake, energy that allows us to communicate in the modern world, and energythat allows for life on earth at all. Our observations of the earth from space are also dependent on waves, those that are received by satellites. Thus, waves are a basic feature of the natural world and our ability to understand waves has resulted in many useful devices, cell phones, garage door openers, and microwave ovens, to name a few.
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What a TSUNAMI is...
A tsunami (pronounced TSOO-NAH-MEE) is a wave train, or series of waves, generated in a body of water by an impulsive disturbance that vertically displaces the water column. Earthquakes, landslides, volcanic eruptions, explosions, and even the impact of cosmic bodies, such as meteorites, can generatetsunamis. Tsunamis can savagely attack coastlines, causing devastating property damage and loss of life. A tsunami can also be called "seismic sea wave", because they're similar to seismic waves but travel through the ocean instead of through land.
What TSUNAMI means...
Tsunami is a Japanese word with the English translation, "harbor wave". Represented by twocharacters, the top character, "tsu", means harbor, while the bottom character, "nami", means "wave". In the past, the scientific community sometimes referred to tsunamis as "tidal waves". The term "tidal wave" is a misnomer; although a tsunami's impact upon a coastline is dependent upon the tidal level at the time a tsunami strikes, tsunamis are unrelated to the tides. Tides result from the imbalance,extraterrestrial, gravitational influences of the moon, sun, and planets. The term "seismic sea wave" is also misleading. "Seismic" implies an earthquake-related generation mechanism, but a tsunami can also be caused by a non-seismic event, such as a landslide or meteorite impact.
How EARTHQUAKES generate TSUNAMIS...
Tsunamis can be generated when the sea floorabruptly deforms and vertically displaces the overlying water. Tectonic earthquakes are a particular kind of earthquake that are associated with the earth's crustal deformation; when these earthquakes occur beneath the sea, the water above the deformed area is displaced from its equilibrium position. Waves are formed as the displaced water mass, which acts under the influence of gravity, attempts toregain its equilibrium. When large areas of the sea floor elevate or subside, a tsunami can be created. Tsunamis travel outward in all directions from the epicenter of an earthquake.
Large vertical movements of the earth's crust can occur at plate boundaries. Plates interact along these boundaries called faults. Around the margins of the Pacific Ocean, for example, denser oceanic plates slip undercontinental plates in a process known as subduction. Subduction earthquakes are particularly effective in generating tsunamis.
What happens to a TSUNAMI as it approaches land...
As a tsunami leaves the deep water of the Open Ocean and travels into the shallower water near the coast, it transforms. The tsunami's energy flux, which is dependent on both its wave speedand wave height, remains nearly constant. Consequently, as the tsunami's speed diminishes as it travels into shallower water, its height grows. Because of this shoaling effect, a tsunami, imperceptible at sea, may grow to be several meters or more in height near the coast. When it finally reaches the coast, a tsunami may appear as a rapidly rising or falling tide, a series of breaking waves, or...
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