SCIENCE QR4

• Earthquake


  Sudden movement or vibration of the Earth's rocky outer layer
• Volcanic earthquake


  Earthquake caused by the movement of magma beneath the surface of the Earth
• The Earth continuously changes over time, and earthquake and volcanic activities modify the landscape in a random and remarkable way over a long period of time
• Earthquakes happen when two large pieces of the Earth's crust suddenly slip
• Crustal plates

  The outer shell of the Earth
• Fault line


  The surface along which the crustal plates move
• Seismometer


  Instrument that responds to ground noises and shaking such as caused by earthquakes, volcanic eruptions, and explosions
• Magnitude

  The energy released by an earthquake at the focus, calculated from earthquakes recorded by a seismograph
• Intensity


  The strength of an earthquake perceived and felt by people in a certain locality, generally higher near the epicenter
• Magnitude is a quantitative measure of an earthquake's strength in terms of energy released, while intensity is an indicator of the severity of shaking generated at a given location
• Focus


  The actual location where fault movement begins, below the Earth's surface
• Epicenter


  The point at the land surface directly above the focus
• Types of natural earthquakes

  • Tectonic earthquakes
  • Volcanic earthquakes
• Tectonic earthquakes


  Produced by sudden movement along faults and plate boundaries
• Volcanic earthquakes


  Produced by the movement of magma beneath the volcanoes
• The difference between tectonic and volcanic earthquakes is that tectonic earthquakes cause collapse of different structures, while volcanic earthquakes cause explosions
• Cause of volcanic eruption

  Movement of magma beneath the surface of the Earth, resulting in pressure changes and stress on the crust
• Scientists cannot predict earthquakes, but they can point out where fault lines are to know where earthquakes are likely to occur
• The largest earthquake ever recorded was in Chile in 1960, measuring 9.6 on the Richter scale, and the largest in the U.S. was a 9.2 magnitude in Alaska in 1964
• Earthquakes can cause huge waves in the ocean called tsunamis, and the movement of tectonic plates can form large mountain ranges like the Himalayas and the Andes
• Earthquakes can happen in any kind of weather