Conservative (Passive) Plate Boundaries


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Conservative (Passive) Plate Boundaries

  1. 1. Conservative (Passive) Plate Boundaries
  2. 2. Along the “meeting point” a fault line is created where One plate moves in one huge friction is caused that direction, as the other(s) results in an earthquake. go(es) in the opposite direction. In the mean time a gap is created behind each of the plates as it moves forward and this is called a fault.
  3. 3. • Conservative (Passive) plate boundaries occur where two plates slide horizontally past each other. This does not cause the loss or creation of land although as each plate moves in the opposite direction to the other, huge friction is caused. This results in an earthquake as the Earth is shaken by the movement of the two huge masses of rock, due to the enormous amount of energy being released; and these effects are particularly felt in buildings on the fault line where the two plates meet. The areas behind each plate where a gap is left also shake as they “fall” momentarily. • The best known example of a Conservative (Passive) plate boundary can be found along the west coast of the USA where the Pacific Plate is moving in a North Westerly direction and sliding past the North American Plate. This plate boundary is the cause of the San Andreas Fault. Other examples of this type of fault include the Alpine Fault in New Zealand and the North Anatolian Fault in Turkey.
  4. 4. The San Andreas Fault
  5. 5. The San Andreas Fault is a geological fault that runs a length of roughly 800 miles through western and southern California in the United States. The fault, a right-lateral strike-slip fault, marks a transform (or sliding) boundary between the North American Plate and the Pacific Plate. All land west of the fault on the Pacific Plate is moving slowly to the northwest while all land east of the fault is moving to the southwest (relatively southeast as measured at the fault) under the influence of plate tectonics. It slices California in two from Cape Mendocino to the Mexican border. San Diego, Los Angeles and Big Sur are on the Pacific Plate. San Francisco, Sacramento and the Sierra Nevada are on the North American Plate. The rate of slippage averages approximately 33-37 mm/year across California. This fault effects both Los Angeles and San Francisco. Projected motion indicates that the Gulf of California will expand northward at the same time that the landmass west of the fault, including the Baja California peninsula and the California coast slides past San Francisco, then continuing north-westward as an island mass toward the Aleutian Trench, over a period of around twenty million years.
  6. 6. The arrows on this image show the relative motion of the two plates. The plate to the left of the map is the Pacific Plate, meaning the plate to the right is the North American Plate. As you can see the two plates are moving in opposite directions to one another. Blocks on opposite sides of the San Andreas fault move horizontally. If a person stood on one side of the fault and looked across it, the block on the opposite side would appear to have moved to the right. Geologists refer to this type fault displacement as right- lateral strike-slip. This is a movement which has occurred along the fault.
  7. 7. In the recent past, scientists have attempted to predict when the next big earthquake will occur on the San Andreas Fault. In the late 1980s they predicted that in 1993 an earthquake would occur, however this did not happen until 2004 in Parkfield. To predict this they used previous figures and dates and decided that 1993 would probably be the next date for an event of huge scale in this area. Even though these predictions are becoming more and more accurate they will never be 100% correct and no-one truly knows when the next potential humanitarian disaster will happen.
  8. 8. This map indicates all of the places effected by the San Andreas Fault including large cities such as Los Angeles and San Francisco.
  9. 9. 1906 San Francisco Earthquake
  10. 10. On the 18th of April, 1906 San Francisco experienced a huge earthquake, with modern estimates giving the disaster a rating of 8.5 on the Richter Scale. The earthquake was caused by the two main plates in the area rubbing against each other thus creating a huge amount of friction. The main shock epicenter occurred offshore about 2 miles from the city, near Mussel Rock. It ruptured along the San Andreas fault both northward and southward for a total length of 296 miles. San Francisco was devastated by the event as buildings were destroyed and therefore livelihoods ruined and this was worsened by the subsequent fires. The economic impact has been compared with the more recent Hurricane Katrina disaster . The tremors caused by the quake could be felt up to 80 miles from the fault. 700 people were killed in San Francisco with another 189 fatalities reported in other areas of the west coast of the USA. The earthquake caused the displacement of the mass majority of San Franciscans and in response 11 refugee camps were built. Since this event the area has been hit by many more earthquakes, most notably in 1989. However such natural disasters can never be stopped as the area will always lie on the San Andreas Fault.
  11. 11. By James Benson, Tom Hill, Joe Taylor, Lewis Herdson And Jack Sherlock