Earthquakes & Volcanoes


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Notes over Prentice Hall chapter 2 in their book Dynamic Earth

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Earthquakes & Volcanoes

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