Earth science

• Earthquakes are a natural hazard that can cause seismic shaking, liquefaction, landslides and mudflows, tsunamis, and fires.
• Seismic shaking is ground vibration caused by seismic waves that can cause structures to jolt and twist, with the strongest shaking closest to the epicenter.
• Liquefaction occurs in areas where soil and rock are saturated with water, causing pores to fill with water and no longer support buildings, resulting in soil acting like liquid and causing buildings and structures to collapse.
• Earthquakes can trigger mass movements, causing landslides and mudflows.
• Tsunamis are a series of waves when the ocean floor shifts during an earthquake.
• Fires are not a natural effect of earthquakes, but can be caused by broken gas mains, spilled liquid fuel, overturned fires and lamps.
• We can look at geologic history and historic record of activity to predict the probability of an earthquake occurring along a fault.
• The goal of earthquake prediction is to predict when and where earthquakes will strike, based on precursors such as small foreshocks, change in well-levels, electromagnetic waves, and animal behavior.
• Earthquake safety measures include seismic gap, an area along a fault where there has not been earthquake activity for a long period of time, and seismic safe design, which involves building codes for earthquake resistant structures, steel frames reinforced with cross braces.
• During an earthquake, the drop, cover, hold method is recommended, which involves dropping to the ground, covering your head with your arms, and holding onto something sturdy.
• Avoid windows, mirrors, and furniture that might topple during an earthquake.
• If outdoors, move to an open area during an earthquake.
• 3 major Layers:

  crust, mantle, core
• Mantle - middle layer
• Crust - outermost layer
• Core - innermost layer

  oceanic and continental
• Core - outer core (liquid) & inner core (solid)
• Crust - thin solid shell on top of earth's interior layers
• Continental crust - thicker than oceanic crust
• lithosphere- crust and outermost mantle—> rigid mantle
• Asthenosphere - easily deformed rocks amd weaker than than the lithosphere
• Lower mantle: 660km deep to the base of the mantle, rigid layer
• inner and outer core

  • composed of mostly: iron and nickel
  • outer core= liquid
  • metallic iron creates magnetic field
  • inner core compresses materials into solids by pressure
• Seismic waves bend as they travel throughout earth
• the study of P and S waves help identify outer core as liquid
• velocity of seismic waves increased 50 km below earths surface
• moho boundary is between the crust and the upper mantle—> between the lithosphere and asthenosphere
• P waves bent around the outer core
• outer core causes P waves to arrive later
• S waves can not pass through