"Great" Earthquake Fault Blocks

Pacific Ocean Great Earthquakes & Tsunamis

In these earthquake activities you will create subduction zone earthquake blocks showing how great earthquakes are generated by the movement of an ocean plate moving beneath another plate. 

Ninety percent of great earthquakes and tsunamis occur in the Pacific Ocean in subduction zones.  These earthquake activities show how the plates can lock and pressure builds until a great earthquakes occurs sending tsunami waves to distant shores. 

Megathrust fault blocks, Photo by Myrna Martin

Materials

  • 7 x 8 x 2 inch Styrofoam block
  • Paint (blue, green, grey, and brown)
  • Paint brush
  • Sharp knife (adult helper needed)

Directions

  1. Have an adult cut the Styrofoam block at an angle the length of the block with a sharp kitchen knife.
  2. Rub the two cut edges together to break off the rough edges and smooth the cut surfaces.
  3. Paint the Styrofoam pieces like the picture. The green, grey and brown side represents a continental plate. The blue and brown side represents an oceanic plate.
  4. After the blocks are dried hold the plates together while pushing the oceanic plate beneath the continental plate.
  5. A loud noise should be heard with the sudden downward movement of the oceanic plate.

There are many fun science activities in this book that show how earthquakes can cause the land to shake, rattle, and roll  beneath our feet.      Myrna Martin

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Science behind the activity

Megathrust earthquakes that occur in subduction zones can be hundreds of kilometers long. The ocean floor often slips downward and sideways during one of these events.

On December 26, 2004 a megathrust earthquake occurred when the rocks broke along a fault line in the Indian Ocean approximately 1600 km long. The entire length of the break and the seafloor lifted several feet creating tsunami waves and vibrations recorded around the entire Earth by seismographs for an entire week after the event.


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