full transcript

From the Ted Talk by Alex Gendler: How tsunamis work

Unscramble the Blue Letters

In 479 BC, when Persian soldiers besieged the Greek city of Potidaea, the tide raeetertd much farther than usual, leaving a convenient invasion route. But this wasn't a stroke of luck. Before they had crossed halfway, the water returned in a wave higher than anyone had ever seen, drowning the attcrkeas. The Potiidaeans believed they had been saved by the wrath of Poseidon. But what really saved them was likely the same phenomenon that has destroyed countless others: a tsunami. Although tsunamis are coonmmly known as tidal waevs, they're actually uetenrlad to the tidal activity cueasd by the giittaonavarl forces of the Sun and Moon. In many ways, tsunamis are just larger versions of regular waves. They have a togurh and a cerst, and consist not of moving water, but the movement of energy through water. The difference is in 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 ernegy originating underwater, from a volcanic eruption, a submarine landslide, or most commonly, an earthquake on the ocean floor caused when the tectonic plates of the Earth's surface slip, releasing a massive amount of energy into the water. This energy telrvas up to the surface, displacing water and raising it above the normal sea level, but gravity pulls it back down, which makes the energy ripple outwards horizontally. Thus, the tsunami is born, moving at over 500 meils per hour. When it's far from srhoe, a tsunami can be berlay detectable since it moves through the enrtie depth of the water. But when it reaches shallow water, something celald wave saholnig occurs. Because there is less water to move through, this still massive amount of energy is compressed. The wave's speed slows down, while its height rises to as much as 100 feet. The word tsunami, Japanese for "harbor wave," comes from the fact that it only seems to appear near the coast. If the trough of a tsunami raehces shore first, the water will withdraw farther than normal before the wave hits, which can be misleadingly dangerous. A tsunami will not only dworn people near the coast, but level buildings and teers for a mile inland or more, especially in low-lying areas. As if that weren't enough, the waetr then retreats, dragging with it the nlwey created debris, and anything, or anyone, unfortunate enough to be caught in its path. The 2004 Indian Ocean tsunami was one of the deadliest natarul disasters in history, killing over 200,000 ppolee throughout South Asia. So how can we perotct ourselves against this destructive fcore of nature? People in some areas have attempted to stop tsunamis with sea walls, flood gates, and channels to divert the water. But these are not always evtfiefce. In 2011, a tsunami surpassed the foold wall protecting Japan's fkmhuusia Power Plant, causing a nuclear disaster in aiidtdon to claiming over 18,000 lives. Many scientists and policy makers are instead focusing on early dceioettn, monitoring uenetadrwr pressure and seismic activity, and establishing global communication nowktres for qukcily distributing alerts. When nature is too pewruofl to stop, the safest course is to get out of its way.

Open Cloze

In 479 BC, when Persian soldiers besieged the Greek city of Potidaea, the tide _________ much farther than usual, leaving a convenient invasion route. But this wasn't a stroke of luck. Before they had crossed halfway, the water returned in a wave higher than anyone had ever seen, drowning the _________. The Potiidaeans believed they had been saved by the wrath of Poseidon. But what really saved them was likely the same phenomenon that has destroyed countless others: a tsunami. Although tsunamis are ________ known as tidal _____, they're actually _________ to the tidal activity ______ by the _____________ forces of the Sun and Moon. In many ways, tsunamis are just larger versions of regular waves. They have a ______ and a _____, and consist not of moving water, but the movement of energy through water. The difference is in 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 ______ originating underwater, from a volcanic eruption, a submarine landslide, or most commonly, an earthquake on the ocean floor caused when the tectonic plates of the Earth's surface slip, releasing a massive amount of energy into the water. This energy _______ up to the surface, displacing water and raising it above the normal sea level, but gravity pulls it back down, which makes the energy ripple outwards horizontally. Thus, the tsunami is born, moving at over 500 _____ per hour. When it's far from _____, a tsunami can be ______ detectable since it moves through the ______ depth of the water. But when it reaches shallow water, something ______ wave ________ occurs. Because there is less water to move through, this still massive amount of energy is compressed. The wave's speed slows down, while its height rises to as much as 100 feet. The word tsunami, Japanese for "harbor wave," comes from the fact that it only seems to appear near the coast. If the trough of a tsunami _______ shore first, the water will withdraw farther than normal before the wave hits, which can be misleadingly dangerous. A tsunami will not only _____ people near the coast, but level buildings and _____ for a mile inland or more, especially in low-lying areas. As if that weren't enough, the _____ then retreats, dragging with it the _____ created debris, and anything, or anyone, unfortunate enough to be caught in its path. The 2004 Indian Ocean tsunami was one of the deadliest _______ disasters in history, killing over 200,000 ______ throughout South Asia. So how can we _______ ourselves against this destructive _____ of nature? People in some areas have attempted to stop tsunamis with sea walls, flood gates, and channels to divert the water. But these are not always _________. In 2011, a tsunami surpassed the _____ wall protecting Japan's _________ Power Plant, causing a nuclear disaster in ________ to claiming over 18,000 lives. Many scientists and policy makers are instead focusing on early _________, monitoring __________ pressure and seismic activity, and establishing global communication ________ for _______ distributing alerts. When nature is too ________ to stop, the safest course is to get out of its way.

Solution

  1. reaches
  2. waves
  3. gravitational
  4. powerful
  5. entire
  6. fukushima
  7. retreated
  8. energy
  9. unrelated
  10. effective
  11. commonly
  12. caused
  13. shoaling
  14. force
  15. called
  16. flood
  17. attackers
  18. newly
  19. natural
  20. barely
  21. networks
  22. underwater
  23. drown
  24. shore
  25. trees
  26. trough
  27. water
  28. people
  29. addition
  30. travels
  31. crest
  32. protect
  33. detection
  34. quickly
  35. miles

Original Text

In 479 BC, when Persian soldiers besieged the Greek city of Potidaea, the tide retreated much farther than usual, leaving a convenient invasion route. But this wasn't a stroke of luck. Before they had crossed halfway, the water returned in a wave higher than anyone had ever seen, drowning the attackers. The Potiidaeans believed they had been saved by the wrath of Poseidon. But what really saved them was likely the same phenomenon that has destroyed countless others: a tsunami. Although tsunamis are commonly known as tidal waves, they're actually unrelated to the tidal activity caused by the gravitational forces of the Sun and Moon. In many ways, tsunamis are just larger 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 is in 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 energy originating underwater, from a volcanic eruption, a submarine landslide, or most commonly, an earthquake on the ocean floor caused when the tectonic plates of the Earth's surface slip, releasing a massive amount of energy into the water. This energy travels up to the surface, displacing water and raising it above the normal sea level, but gravity pulls it back down, which makes the energy ripple outwards 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 through the entire depth of the water. But when it reaches shallow water, something called wave shoaling occurs. Because there is less water to move through, this still massive amount of energy is compressed. The wave's speed slows down, while its height rises to as much as 100 feet. The word tsunami, Japanese for "harbor wave," comes from the fact that it only seems to appear near the coast. If the trough of a tsunami reaches shore first, the water will withdraw farther than normal before the wave hits, which can be misleadingly dangerous. A tsunami will not only drown people near the coast, but level buildings and trees for 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 deadliest natural disasters in history, killing over 200,000 people throughout South Asia. So how can we protect ourselves against this destructive force of nature? People in some areas have attempted to stop tsunamis with sea walls, flood gates, and channels to divert the water. But these are not always effective. In 2011, a tsunami surpassed 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 makers are instead focusing on early detection, monitoring underwater pressure and seismic activity, and establishing global communication networks for quickly distributing alerts. When nature is too powerful to stop, the safest course is to get out of its way.

Frequently Occurring Word Combinations

ngrams of length 2

collocation frequency
massive amount 2

Important Words

  1. activity
  2. addition
  3. affects
  4. alerts
  5. amount
  6. areas
  7. asia
  8. attackers
  9. attempted
  10. barely
  11. bc
  12. believed
  13. besieged
  14. born
  15. buildings
  16. called
  17. caught
  18. caused
  19. causing
  20. channels
  21. city
  22. claiming
  23. coast
  24. commonly
  25. communication
  26. compressed
  27. consist
  28. convenient
  29. countless
  30. created
  31. crest
  32. crossed
  33. dangerous
  34. deadliest
  35. debris
  36. depth
  37. destroyed
  38. destructive
  39. detectable
  40. detection
  41. difference
  42. disaster
  43. disasters
  44. displacing
  45. distributing
  46. divert
  47. dragging
  48. drown
  49. drowning
  50. early
  51. earthquake
  52. effective
  53. energy
  54. entire
  55. eruption
  56. establishing
  57. fact
  58. feet
  59. flood
  60. floor
  61. focusing
  62. force
  63. forces
  64. fukushima
  65. gates
  66. global
  67. gravitational
  68. gravity
  69. greek
  70. halfway
  71. height
  72. higher
  73. history
  74. hits
  75. horizontally
  76. hour
  77. indian
  78. inland
  79. invasion
  80. japanese
  81. killing
  82. landslide
  83. larger
  84. leaving
  85. level
  86. limited
  87. lives
  88. luck
  89. makers
  90. massive
  91. mile
  92. miles
  93. misleadingly
  94. monitoring
  95. moon
  96. move
  97. movement
  98. moves
  99. moving
  100. natural
  101. nature
  102. networks
  103. newly
  104. normal
  105. nuclear
  106. occurs
  107. ocean
  108. originating
  109. outwards
  110. path
  111. people
  112. persian
  113. phenomenon
  114. plant
  115. plates
  116. policy
  117. poseidon
  118. potidaea
  119. potiidaeans
  120. power
  121. powerful
  122. pressure
  123. protect
  124. protecting
  125. pulls
  126. quickly
  127. raising
  128. reaches
  129. regular
  130. releasing
  131. retreated
  132. retreats
  133. returned
  134. ripple
  135. rises
  136. route
  137. safest
  138. saved
  139. scientists
  140. sea
  141. seismic
  142. shallow
  143. shoaling
  144. shore
  145. size
  146. slip
  147. slows
  148. soldiers
  149. south
  150. speed
  151. stop
  152. stroke
  153. submarine
  154. sun
  155. surface
  156. surpassed
  157. tectonic
  158. tidal
  159. tide
  160. travels
  161. trees
  162. trough
  163. tsunami
  164. tsunamis
  165. underwater
  166. unfortunate
  167. unrelated
  168. usual
  169. versions
  170. volcanic
  171. wall
  172. walls
  173. water
  174. wave
  175. waves
  176. ways
  177. wind
  178. withdraw
  179. word
  180. wrath