Tsunamis

Daily Dose of Destruction

Not only are earthquakes dangerous because of all the shaking that they do, but earthquakes also can produce one of the most powerful and deadly forces on Earth, tsunamis.  A tsunami is an energetic wave caused by earthquakes, landslides, and underwater volcanic eruptions.  When an earthquake hits underwater, it can produce a landslide, or when a volcano erupts underwater or collapses into the water, water is displaced.  Imagine yourself doing a belly flop into a calm, still pool of water.  The reason waves are generated is that your body displaced or moved water out of the way to make room for you.  The energy of your falling into the water is transferred to the water molecules and one molecule after another receives that energy.  When an earthquake breaks at a fault line in the ocean, if it displaces water, a tsunami will be generated.  Seiches are lake tsunamis or large waves in lakes.  Seiches can also be caused by heavy and prolonged winds on lakes.

Tsunamis can travel thousands of miles.  In the open ocean, you might not even feel or see the tsunami.  The energy doesn't create a big wave until it gets closer to the shoreline.  Sensitive instruments found in the oceans near many countries can detect the energy, thereby having time to sound a tsunami warning.  Tsunamis can reach 30 meters high, but there have been a few that are much much taller.  Many times the ocean will recede from the shore giving a warning itself that a tsunami is on its way.  Below is a video that does a great job explaining how a tsunami is formed.

Below is a list of four of the largest tsunamis to have ever been witnessed.

• Lituya Bay Alaska
  • 1958
  • Caused part of a mountain to collapse into the bay.
  • Estimated at 1720 feet, about a quarter of a mile high.  Knocked trees down halfway up some of the mountains.
• Spirit Lake Washington
  • 1980
  • 853 feet 
  • Caused by Mount St. Helens eruption landslide
• Shoup Bay, Alaska
  • 220 feet
  • 1964 on Good Friday
  • Caused by a 9.2-magnitude Earthquake
  • Followed by 20 smaller tsunamis caused by underwater landslides from the quake
  • Waves hit 20 different countries
  • Killed 106 including 13 in California
  • Here are two videos discussing the Shoup Bay tsunami.

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• Sanriku Japan
  • 1896
  • 125 feet
  • Caused by an 8.5 magnitude  Earthquake
  • Killed 22,000
  • Two different powerful waves hit during a celebration
  • Boats out in the ocean didn't even notice.  The next morning they came to shore to discover the horrific scene.
  • 30-foot waves hit Hawaii killing people there as well.

Below is a documentary of the 2004 Boxing Day Tsunami that killed 250,000 people.  The video contains stories of some survivors who videotaped much of it. It has been edited of language and graphic scenes I deemed too horrific for even high schoolers to see.