NATSCI4_Intro-to-Hazards

• Philippines has experienced the most natural hazards in the 20th century.
• India is the second nation to have experienced the most natural hazards in the 20th century.
• United States is the third nation to have experienced the most natural hazards in the 20th century.
• A Geohazard or Natural Hazard is an unexpected or uncontrollable natural event of unusual magnitude that threatens the activities of people or people themselves (Risk).
• A natural disaster is a natural hazard event that resulted in widespread destruction of property or caused injury and/or death.
• A catastrophe is a massive disaster, requiring significant expenditure of time and money for recovery.
• These are benefits of natural hazards:

  1. River flooding supplies nutrients to floodplains
  2. Flooding causes erosion on mountain slopes, delivering sediments to beaches from rivers and flushing pollutants
  3. Landslide debris from dams, making lakes in mountainous areas.
  4. Earthquakes are also important in mountain building
  5. Volcanic eruptions create new land
• Risk analysis is an important component in our understanding of the effects of hazardous processes.
• Risk is = probability of the event occurring X consequences when the event occurs
• Risk analysis is the estimates of risk.
• The problem with risk analysis is that there is a lack of reliable data for analyzing either the probability or the consequences of an event.
• Earthquakes can produce landslides and tsunamis.
• Typhoons can cause flooding and coastal erosion.
• The magnitude, frequency, and severity of hazardous events may be influenced by human activity.
• We cope with natural hazards through:

  1. Adaptation
  2. Mitigation
• Mitigation is the process of reducing the severity of the impact of natural hazards through planning.
• Mitigation is the avoidance of, lessening, or compensation for anticipated harmful effects of an action with respect to the natural environment.
• Each hazard requires a specific type of mitigation like engineering solutions (e.g. earthquake-resistant building) to at least temporarily reduce the impact of the hazard.
• Only form of mitigation that is guaranteed to be successful is to limit or not allow human activities where hazards occur.
• Examples of ways to cope with natural disasters

  • Hazard Perception
  • Land-use Planning
  • Artificial Control of Natural Processes
  • Insurance
  • Evacuation
  • Disaster Preparedness
• There are hazard-prone areas in the world because of plate tectonics
• Plate tectonics are also called Lithospheric plates.
• Lithosphere is the Earth’s outer shell.
• The Earth's Lithosphere consists of seven major plates.
• The Earth's Lithosphere consists of numerous smaller segments called plates that are in motion relative to each other.
• Most of Earth’s seismic activity, volcanism, and mountain building occur along the dynamic margins of the Earth's plates.
• The large Lithospheric plates contain both continental and oceanic crust and the entire plate moves.
• The Major Lithospheric Plates are:

  1. North American
  2. South American
  3. Pacific
  4. African
  5. Eurasian
  6. Australian
  7. Antarctic
• The largest major Lithospheric plate is the Pacific.
• The Minor Lithospheric plates are:

  1. Caribbean
  2. Nazca
  3. Philippine Sea
  4. Arabian
  5. Cocos
  6. Scotia
• The 3 types of plate boundaries are:

  1. Divergent
  2. Convergent
  3. Transform
• The tectonic setting in the Philippines consist of:

  1. Pacific Ring of Fire
  2. Philippine Fault Zone
• The Pacific Ring of Fire is also referred to as the Circum-Pacific Belt.
• The Pacific Ring of Fire is a path along the Pacific Ocean characterized by active volcanoes and frequent earthquakes.
• The majority of Earth’s volcanoes and earthquakes take place along the Ring of Fire.
• The PFZ or Philippine Fault Zone is a major tectonic feature that transects the whole Philippine archipelago from northwestern Luzon to southeastern Mindanao, which measures 1,200 km.
• The Philippine Fault Zone is an arc-parallel, left-lateral strike-slip fault, divided into several segments.
• The Philippine Fault Zone is the source of large-magnitude earthquakes in recent years.
• The 1973 Ragay Gulf earthquake had a magnitude of 7.0.
• The 1990 Luzon earthquake had a magnitude of 7.7.