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Earthquakes

Earthquakes. And. Volcanoes. Shaking and trembling of the earth’s crust. The waves travel in all directions More than 1,000,000 occur a year or one every 30 seconds Faulting is the most common cause Earthquakes continue until all the energy is used up

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Earthquakes

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  1. Earthquakes And Volcanoes

  2. Shaking and trembling of the earth’s crust. The waves travel in all directions More than 1,000,000 occur a year or one every 30 seconds Faulting is the most common cause Earthquakes continue until all the energy is used up TSUNAMIS- are caused by earthquakes on the ocean floor: causing waves to become greater than 20 meters high San Andreas Fault- located in California, U.S. most famous, strike slip fault at a transform boundary. Pacific plate moves northwest past the North American plate. Defining Earthquakes

  3. Seismic Waves • FOCUS- underground point of origin (where the quake begins) • EPICENTER- aboveground of origin; most violent shaking occurs at the epicenter (directly above the focus) • The three main types of seismic waves are: P waves, S waves, and L waves (surface waves)

  4. P Waves • Primary waves • Arrive first and are the fastest waves • Can travel through solids, liquids, and gases • They are push-pull waves

  5. S Waves • Secondary waves • Can travel through solids, but NOT through liquids and gases • Moves in up-down motion

  6. Surface/L Waves • Surface waves • Slowest moving seismic waves • Travel on top of Earth’s surface • Cause most of damage to Earth, because they bend and twist the surface

  7. The MOHO A place within the Earth where the speed of seismic waves increase sharply; marks the boundary between the earth’s crust and mantle. The red line in the drawing below shows its location.

  8. John Milne- 1893 • Seismograph-measures and detects seismic waves • Seismogram- Paper record of waves • Seismologist- scientist who study earthquakes • Richter Scale-a scale that allows scientists to determine earthquake strength based on many readings • 1-10 levels at which an earthquake is measured on amount of damage caused; Above a 6 is very destructive

  9. Magnitude- is the number geologists assign to an earthquakes size. Mercalli scale- this scale rates earthquakes according to the level of damage at a given place.Moment magnitude scale- rating system that estimates the total energy released by a quake.

  10. VOLCANOES • Volcano- place on Earth’s surface that allows magma and other material to erupt • Magma- found beneath the Earth’s surface, it is liquid rock • Lava- magma that reaches the Earth’s surface

  11. Volcanic Dust- less that 0.25 mm in diameter (flour) Volcanic Ash- more than 0.25 but less than 5 mm (rice) Volcanic Bombs- few cm to several meters. Cinders- volcanic bombs the size of golf balls Volcanic Fragments

  12. Types of Volcanoes • Cinder Cones- made of mostly of cinders; formed from explosive eruptions • Shield- Made of quiet lava flows • Composite- made up of alternating layers of rock particles; explosive eruptions, then quite lava flows

  13. Crater- funnel shaped pit, or depression at top of volcano Caldera- when a crater becomes too large, it collapses: also can form when the top of a volcano collapses or explodes Dormant- sleeping volcano Extinct- not known to have erupted in modern history Active- Erupts fairly regularly Volcanic Terminology

  14. Ring of Fire

  15. Ring of FireThe Ring of Fire is an area where large numbers of earthquakes and volcanic eruptions occur in the basin of the Pacific Ocean.The Ring of Fire is a direct result of plate tectonicsand the movement and collisions of crustal plates.About 90% of the world's earthquakes and 80% of the world's largest earthquakes occur along the Ring of Fire.75% of the worlds active and dormant volcanoes are found here(452volcanoes are located in or around the Ring of Fire).

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