science

• Continental Drift Hypothesis


  Proposes that the continents were assembled to form the super continent Pangaea
• Continental Drift Theory


  Alfred Wegener believed landmasses of Earth once fit together to form single landmass called "Pangaea"; landmasses "drifted" to where they are today; theory disregarded due to lack of evidence
• Alfred Wegener


  Proposed the continental drift theory in the 1900s
• Fit of Continents


  • Antonio Snider-Pelligrini (1858) a geographer cut out a map of Africa and south america suggesting they were connected at one time
  • Other Physical evidence based on observation was used by Wegener
• Fossil Evidence


  • Similar terrestrial species were found on many continents now separated by oceans
  • Information collected by paleontologists
• Ancient Mountain Ranges


  • The same sequence of rocks is found in North America, Great Britain, and Norway. The pattern does not make sense with the continents in their current configuration
• Evidence of Ancient Glaciers


  • Glaciers carve rocks as they move
  • Scientists can determine the direction of movement (notice the direction of movement noted in South America)
  • As South America sits today, the pattern would not make sense. (glaciers do not move from sea level to higher elevations
• Wegner's idea was not accepted by the scientific community because he could not explain how the continents moved
• Seafloor features


  • Mid-oceanic ridges
  • Trenches
  • Volcanism adjacent to trenches
  • Seamounts
  • Fracture zones
• Seafloor Spreading


  Mafic lava is extruded along the mid-oceanic ridge to produce ocean floor<|>New material is added, the cooler material is split and is "pushed" away from the ridge
• Mafic lava


  Dark-colored lava rich in magnesium and iron
• Drive Mechanisms


  • Convection cells within the mantle
  • Pushing at the mid-oceanic ridges
  • Pulling at the subduction zones
• Plate boundaries


  Divergent, convergent, transform
• Divergent Boundary


  Variant, moving apart
• Convergent Boundary


  A plate boundary where two plates move toward each other
• Transform Boundary


  A plate boundary where two plates move past each other in opposite directions
• Continental boundary


  The boundary between two continental plates
• Oceanic boundary


  A boundary that is covered by ocean water
• Types of earthquake


  • Shallow Fault Earthquake
  • Subduction Earthquake
  • Deep Earthquake
• Shallow Fault Earthquakes


  This is a type of earthquake that breaks the rock beneath our feet. Shallow fault quakes occur very close to the surface.Shallow fault earthquakes are so near the surface, even smalls one causes a lot of damage from shaking.
• Subduction Zone Earthquake


  The largest earthquake ever recorded are subduction zone earthquakes. They can last several minutes. Subduction zone shaking can occur along the whole subduction zone.In the Pacific Northwest, these major earthquakes seem to occur every few hundred years. The last known subduction zone earthquakes along the Oregon and Washington coast was January 26,1700. In addition to causing huge shifts in land level here, this quake sent huge waves and tsunamis racing across the pacific.
• Deep Earthquakes


  It occurs in the sub-ducting ocean slab, deep beneath the continental crust. In the Pacific Northwest, deep quakes start about 50 km (30 mi) beneath the surface. Large ones have shaked the Pacific Northwest in 1949, 1965 and 2001 about every 30 years. The last big deep quake, the 2001 Nisqually earthquake occurred under the southern end of Puget sound
• Causes of Earthquake


  Earthquakes are caused by sudden tectonic movements in the Earth's crust. The continuous motion of tectonic plates causes a steady build-up of pressure in the rock strata on both sides of a fault until the stress is sufficiently great that it is released in a sudden, jerky movement. The resulting waves of seismic energy propagate through the ground and over the its surface, causing the shaking we perceive as earthquakes.
• Causes of Earthquake


  • Induced Seismicity
  • Volcanic Tectonic Earthquakes
  • Fault Movement
• Induced Seismicity


  It refers to typically minor earthquakes and tremors that are caused by human activity that alters the stresses and strains on the Earth's crust. Most induced seismicity is of a low magnitude. A few sites regular have larger quakes, such as The Geysers geothermal plant in California which averaged two M4 events and 15 M3 events every year from 2004 to 2009.
• Volcanic Tectonic Earthquakes


  It is an earthquake caused by movement of magma beneath the surface of the Earth. The movement results in pressure changes where the rock around the magma has experienced stress. At some point, this stress can cause the rock to break or move.
• Fault Movement


  It is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movement. Large faults within the Earth's crust result from the action of plate tectonic forces, with the largest forming boundaries between the plates, such as subduction zones or transform fault.
• Causes of Induced Seismicity

  • Volume Changes
  • Increase of Pore Pressure
  • Chemical Changes
  • Thermo-elastic Deformation
  • Load Change
• Precautions before an earthquake

  • Make sure you have an emergency kit
  • Secure heavy furniture
  • Keep a list of emergency numbers
  • Learn how to use first aid kits, switching off the waterlines or gas tanks
• Precautions During an Earthquake (Indoor)


  • Drop, Cover and Hold
  • Stay indoors until shaking stops
  • Before you leave the building check the area
  • If you smell gas, get out of the house as quick as possible
• Precautions During an Earthquake (Outdoor)


  • Find a clear spot to go to and drop to the ground until the shaking stops
  • If in a vehicle pull over to the a clear area
  • If a power line falls on your vehicle, do not go out and wait for assistance
  • If you are in a mountainous area be alert for falling rocks or landslides
• Precautions After an Earthquake


  • If away from home, return only when authorities say that it is safe to go back
  • Check yourself if you have any injuries then get first aid before helping injured or trapped people
  • Be prepared when there is an aftershock, landslide or a tsunami
  • Every time you feel an after shock you drop, cover and hold
  • Extinguish small fires that are near you
• Why do earthquakes occur?

  Fractures<|>Faults<|>Energy released and propagates in all directions as seismic waves causing earthquakes
• Where do Earthquakes occur?


  The edge of the oceanic and continental plate<|>Along faults: normal,reverse transform
• Focus


  Location of initial slip on the fault; where the earthquakes origins
• Epicenter


  Spot on Earth's surface directly above the focus
• 1. Waves


  Called compressional , or push-pull waves<|>Propagate parallel to the direction in which the waves if moving<|>Move through solids,liquids
• 1. waves


  Called shear waves<|>Propagate the movement perpendicular to the direction in which the wave is moving
• Surface waves (L-waves or long waves)

  Complex motion<|>Up-and down and side-to-side<|>Slowest<|>Most damage to structures; buildings
• Velocity


  Function of the physical properties the rock the wave is traveling through<|>Velocity increases with rock density<|>Velocity changes when passing from one material to another (increases/decreases)<|>Liquids; S-waves do not get transmitted through liquid; P-waves slow down