How To Animate Google Earth

in 479 bc, when persian soldiers besieged the greek city of potidaea, the tide retreatedmuch farther than usual, leaving a convenient invasion route. but this wasn't a stroke of luck.

How To Animate Google Earth, before they had crossed halfway, the water returned in a wave higherthan anyone had ever seen, drowning the attackers. the potiidaeans believedthey had been saved

by the wrath of poseidon. but what really saved them was likely the same phenomenonthat has destroyed countless others: a tsunami. although tsunamis are commonlyknown as tidal waves, they're actually unrelatedto the tidal activity caused by the gravitational forcesof the sun and moon. in many ways, tsunamis are justlarger versions of regular waves. they have a trough and a crest,

and consist not of moving water, but the movement of energy through water. the difference isin where this energy comes from. for normal ocean waves,it comes from wind. because this only affects the surface,the waves are limited in size and speed. but tsunamis are caused by energyoriginating underwater, from a volcanic eruption, a submarine landslide, or most commonly,an earthquake on the ocean floor

caused when the tectonic platesof the earth's surface slip, releasing a massive amountof energy into the water. this energy travels up to the surface, displacing water and raising it abovethe normal sea level, but gravity pulls it back down, which makes the energy rippleoutwards horizontally. thus, the tsunami is born, moving at over 500 miles per hour. when it's far from shore,a tsunami can be barely detectable

since it moves throughthe entire depth of the water. but when it reaches shallow water,something called wave shoaling occurs. because there is less waterto move through, this still massive amountof energy is compressed. the wave's speed slows down, while its height risesto as much as 100 feet. the word tsunami,japanese for "harbor wave," comes from the fact that it only seemsto appear near the coast. if the trough of a tsunamireaches shore first,

the water will withdrawfarther than normal before the wave hits, which can be misleadingly dangerous. a tsunami will not only drownpeople near the coast, but level buildings and treesfor a mile inland or more, especially in low-lying areas. as if that weren't enough,the water then retreats, dragging with it the newly created debris, and anything, or anyone,unfortunate enough

to be caught in its path. the 2004 indian ocean tsunami was one of the deadliestnatural disasters in history, killing over 200,000 peoplethroughout south asia. so how can we protect ourselvesagainst this destructive force of nature? people in some areas have attempted to stop tsunamiswith sea walls, flood gates, and channels to divert the water. but these are not always effective.

in 2011, a tsunamisurpassed the flood wall protecting japan's fukushima power plant, causing a nuclear disaster in addition to claiming over 18,000 lives. many scientists and policy makersare instead focusing on early detection, monitoring underwater pressureand seismic activity, and establishing globalcommunication networks for quickly distributing alerts. when nature is too powerful to stop,

the safest courseis to get out of its way.