Science Coronavirus Coverage What families can do now that kids are getting the vaccine. Magazine How one image captures 21 hours of a volcanic eruption. Science Why it's so hard to treat pain in infants. Science The controversial sale of 'Big John,' the world's largest Triceratops. Science Coronavirus Coverage How antivirals may change the course of the pandemic.
Travel A road trip in Burgundy reveals far more than fine wine. Travel My Hometown In L. Subscriber Exclusive Content. Why are people so dang obsessed with Mars? How viruses shape our world. The era of greyhound racing in the U. During a submarine landslide, the equilibrium sea level is altered by sediment moving along the sea floor. Gravitational forces then propagate the tsunami given the initial perturbation of the sea level.
Similarly, a violent marine volcanic eruption can create an impulsive force that displaces the water column and generates a tsunami. Above water landslides and space borne objects can disturb the water from above the surface. The falling debris displaces the water from its equilibrium position and produces a tsunami.
Unlike ocean-wide tsunamis caused by some earthquakes, tsunamis generated by non-seismic mechanisms usually dissipate quickly and rarely affect coastlines far from the source area. Volcanoes can form tsunamis through two mechanisms. Either they collapse or they eject matter with such strength that they uplift the water.
In the first case, land-based volcanoes can also cause tsunamis, if they are very close to the sea. The meteorite works in pretty much the same way, except it creates huge ripples. This kind of tsunamis are really rare, but there is an instance in where such a wave was created by rockfall in Lituya Bay, Alaska.
Tsunamis are not always colossal waves when they come into the shore. Rather, they come in much like very strong and very fast tides i. By now, you should have a pretty clear idea why tsunamis are so dangerous. They can be very long kilometers is a reasonable length , very high the Japan tsunami measured over 10 meters and can travel extremely fast without losing much of their energy.
An earthquake far into the ocean can send several devastating tsunamis hundreds or even thousands of kilometers away. In , an earthquake with the epicenter off the west coast of Sumatra, Indonesia struck with a magnitude of 9. The Indian Plate was subducted by the Burma Plate and triggered a series of devastating tsunamis, some over 30 meters high.
The tsunamis killed over , people in 14 countries, being one of the biggest natural disasters in human history. It is just one in many tragic examples highlighting the sheer force of tsunamis. Since science cannot predict when earthquakes will occur, we cannot determine exactly when a tsunami will be generated. But one property of long waves is that the velocity of propagation grows as the square root of the depth, only depending on it.
In short: the tsunami is harmless but moves at great speed, crossing an ocean in a few hours. When the tsunami approaches the coast, its speed decreases as mentioned above, because the depth decreases. For conservation of energy, if the speed of the wave decreases, its height increases. We can also imagine that water accumulates when braking, increasing the height of the wave. The wavelength also decreases, so the slope of the wave - more height at less distance - grows threateningly.
The wave can break if the slope exceeds a limit. If the coast has a very gentle slope, the tsunami manifests itself as a "rapid tide", in which the sea level rises very rapidly: less than 10 minutes. Sometimes, if the slope of the wave is too steep, the tsunami behaves like a "wall of water" that advances at an angle of about 45 degrees to the ground.
It is the most destructive but least likely case. Finally, it should be noted that tsunamis can be simulated in a computer by numerically solving the equations that describe fluid dynamics.
0コメント