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Earthquakes & Volcanoes
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Earthquakes & Volcanoes



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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    Earthquakes & Volcanoes Earthquakes & Volcanoes Presentation Transcript

    • Earthquakes and Volcanos Earth Science Mr.McKay
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
      • 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
      • 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
      • 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
      • 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
      • 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
    • 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
    • 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
    • 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
      • 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