Earthquakes! I feel the Earth move…

What are they? Shakes Sways Trembles Vibrations

What causes them? Tectonic Plate Movement  Divergent Moving Away Creates a Ridge Example: Mid-Atlantic Ridge Lab Example: Crackers on the frosting  Convergent Coming Together Creates Volcanoes or Mountains Example: Aleutian Islands & Himalayas Lab Example: Cracker/Construction Paper & Soggy Crackers

What causes them?  Transform Sliding Against Fault Lines Example: San Andres Fault Lab Example: Grinding Crackers

Where do they happen? Earthquakes most commonly occur along plate boundaries.

How do they start? The two plates will begin to push and slide against each other  If one rock is weak, it will crumble and the plates will slide easily.  If both rocks are strong, the pressure will build until one finally breaks free.  Think of our fist/knuckles example.  Huge amounts of energy are released.

What is this energy? Seismic Waves  P Waves primary compress like a slinky fastest & loudest  S Waves shear follow the p waves causes surface to ripple  Surface Waves slowest & most destructive move like water ripples

Where is it really happening? Focus  The spot where the seismic energy is being released.  Though always underground, the location can be very shallow or very deep. Epicenter  The spot on the surface where the waves are the strongest.

Measuring Earthquakes Seismograph  picks up the vibrations made by an earthquake  recodes them as a wavy or spiked line  Zhang Heng created the first one

How do we measure them? Richter Scale  Charles Richter  Based on mathematical formula  Described the size or magnitude  Each number is 10 times more powerful than the one before it Mercalli Scale  Giuseppe Mercalli  Describes the damage  Looks at how much an object was shaken  Uses human based observations

Protection from Earthquakes Use materials that have more give like rubber.  In New Zealand flexible joints have been used for water pipelines. Use unconventional building bases.  Springs are placed under the building to absorb the shock.  A set of plates. The bottom plates rest on the ground. During a quake, only the bottom plates move, sliding back and forth under the top plates. Suspension Bridges: Allows the roadway to be hung from one or more towers which support the weight much like a hammock.