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Earthquakes & Volcanoes


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Notes over Prentice Hall chapter 2 in their book Dynamic Earth

Notes over Prentice Hall chapter 2 in their book Dynamic Earth

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  • 1. Earthquakes and Volcanos Earth Science Mr.McKay
  • 2. Earthquakes
    • Earthquake – The shaking and trembling that results from the sudden movement of part of the Earth’s crust
      • Pebble in pond
      • Scientists predict over 1,000,000 earthquakes happen each year
      • Faulting is most common reason for Earthquakes
        • San Andreas Fault
          • Fault Video
  • 3. Tsunamis
    • Tsunami- A huge wave caused by an earthquake on the floor of the ocean
      • They can travel at speeds of 700 to 800 MPH
      • They can reach Heights of 20 meters
        • The height of a 6 Story Building
        • Tsunami Off of Thailand
        • Trouble in Paradise
  • 4. Seismic Waves
    • Earthquake waves are known as seismic waves
      • Focus - The point beneath the Earth’s surface where rocks break and move
        • The focus is the point of origin for the earthquake
      • Epicenter - Directly above the focus on the Earth’s surface
        • Earthquake waves reach the epicenter first
        • Seismic Waves
  • 5. Seismic Waves
    • Primary waves-
      • P-waves: Seismic waves that travel the fastest
        • They arrive at a given point before any other type of wave
        • They travel through
          • Solids
          • Liquids
          • Gases
  • 6. Seismic Waves
    • Primary waves-
      • They move through the Earth differently depending on the material they are traveling through
      • As they move deeper into the Earth, where it is more dense, they move faster
      • They are push-pull waves
  • 7. Seismic Waves
    • Secondary Waves
      • S-Waves – Seismic waves that do not travel through the Earth as fast as P-waves do
      • S-waves arrive at a given point after P-waves do
      • S-waves travel through solids but not liquids and gases
  • 8. Seismic Waves
    • Surface Waves
      • L-waves: They are the slowest moving seismic waves
        • They arrive at a given point after P and S waves
          • They start at the epicenter and move along the Earth’s surface
          • Earth’s surface moves up and down like water waves do
          • They cause the most damage to the Earth because they bend and twist the surface
  • 9. Seismograph
    • Seismograph – An instrument that detects and measures seismic waves
      • Crude Seismographs around for hundreds of years
      • The first practical was made in 1893 by John Milne
      • Consists of
        • A weight attached to a spring or wire
        • A pen attached to the weight that records the movement of the Earth on a paper, that is wound tightly around a constantly moving drum
  • 10.
    • Seismologists – Scientists who study earthquakes
      • PSP Seismograph
      • They can determine the strength of an earthquake by studying the height of the waves
        • They look at a Seismogram
        • They match the seismogram to a chart called the Richter Scale
          • Invented in 1935
          • The scale is from one to ten, with any earthquake above 6 being very destructive
  • 11.
    • Formation
        • High temperature
        • High Pressure
        • Liquid State
        • Found in pockets called magma chambers
      • Magma constantly moves and works its way through cracks toward the surface by melting the solid rock
      • Magma: Rock deep within the Earth
  • 12.
    • Formation
      • Lava – Magma that has reached the Earth’s Surface
      • The place where magma becomes lava is called a Volcano
      • The opening through which lava erupts is called a vent
        • Volcanoes can have more than one vent
          • Lava will poor from the sides of a volcano as well as the top
  • 13.
    • All are not Alike
      • Some are quiet
        • Lava oozes from a vent
      • Others are violent
        • With lava and other material hurled hundreds of feet in the air
        • Gases and earth material mix to be seen from miles away
      • The opening through which lava erupts is called a vent
        • Volcanoes can have more than one vent
          • Lava will poor from the sides of a volcano as well as the top
          • Eruption
  • 14.
    • Scientists study the makeup of the lava that spews from the Volcanoes vents to gain knowledge about the interior magma
    • Types of Lava
      • Dark-colored/ Water
      • Light-colored/ little Water
      • Chemical composition of both
      • Large amounts of gases
        • Steam and carbon dioxide
  • 15. Eruptions
    • During eruptions many rock fragments are blown into the air
      • Smallest = volcanic dust
      • Medium = volcanic ash
      • Large = volcanic bombs
        • Small volcanic bombs the size of golf balls are called Cinders
  • 16. Types of Volcanoes
    • Different types of volcanic eruptions form different types of volcanoes
      • Cinder Cones - made mostly of cinders and other rock particles that have been blown into the air
        • Form from explosive eruptions
        • Cones are not high
        • Narrow base & steep sides
      • Shield Volcanoes – composed of mostly quiet lava flows
        • Gently sloping, domed shaped mountain forms
      • Composite Volcanoes – Built up of alternating layers of rock particles and lava
        • First is a violent eruption
        • Then a quiet eruption
        • After many alternating eruptions a cone shape is formed
  • 17. Types of Volcanoes
    • At the top of a funnel-shaped pit or depression is a pit
      • Called Crater
        • If it becomes to large it is called a Caldera
        • Super Eruption
        • Discovery Channel :: Virtual Super volcano
  • 18.
    • Three Major Zones
      • Nearly all the way around the edge of the Pacific Ocean
        • Called the Ring of Fire
      • Near the Mediterranean Sea
        • Called the Mediterranean Zone
      • Third Extends through Iceland to the middle of the Atlantic Ocean
        • Mid-Atlantic Ridge – Long ridge of volcanoes