Intro

• Common natural hazards


  • flooding
  • Houses buried in the landlides
• It happened when most residents were sleeping in their houses. This new human disaster on Leyte was due to landslides and floods. It had been raining for several days. The ground had become too saturated. Landslides all over the province were the dramatic result. In the same week also in other parts of the Philippines landslides had dramatic results. At least 5250 people were evacuated and more than 220 houses were destroyed in the northeastern part of Mindanao, a region close to Southern Leyte.
• A survivor told:: '"...late at night they heard a thundering sound coming down the mountains, a few minutes later a mud covered their houses...."'
• Types of natural hazards

  • Volcanic eruption
  • Typhoon
  • Earthquake
• Geohazard (Natural hazard)


  An unexpected or uncontrollable natural event of unusual magnitude that threatens the activities of people or people themselves (Risk)
• Natural disaster


  A natural hazard event that resulted in widespread destruction of property or caused injury and/or death
• Catastrophe


  A massive disaster, requiring significant expenditure of time and money for recovery
• Benefits of natural hazards include:

  • River flooding supplies nutrients to floodplains
  • Flooding causes erosion on mountain slopes, delivering sediments to beaches from rivers and flushing pollutants
  • Landslide debris from dams, making lakes in mountainous areas
  • Earthquakes are also important in mountain building
  • Volcanic eruptions create new land
• Risk


  Probability of the event occurring X consequences should the event occur
• Risk analysis is an important component in our understanding of the effects of hazardous processes, but there is a problem of lack of reliable data for analyzing either the probability or the consequences of an event
• Linkages exist between natural hazards and between hazards and the physical environment


  Earthquakes can produce landslides and tsunamis, Typhoons can cause flooding and coastal erosion
• Hazardous events that previously produced disasters are now producing catastrophes, as the magnitude and frequency as well as severity of hazardous events may be influenced by human activity
• Adaptation


  A way to cope with natural hazards
• Mitigation


  The process of reducing the severity of the impact of natural hazards through planning, 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, such as engineering solutions (e.g. earthquake-resistant building) to at least temporarily reduce the impact of the hazard, or limiting or not allowing human activities where hazards occur
• Ways to cope with natural hazards


  • Hazard Perception
  • Land-use Planning
  • Artificial Control of Natural Processes
  • Insurance
  • Evacuation
  • Disaster Preparedness
• Why are there hazard-prone areas in the world?

  Plate Tectonics - Earth's outer shell, called the lithosphere, consists of about seven major and 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 these plates.
• Major Lithospheric Plates


  • North American
  • South American
  • Pacific (largest)
  • African
  • Eurasian
  • Australian
  • Antarctic
• Minor (intermediate-sized) Lithospheric Plates


  • Caribbean
  • Nazca
  • Philippine Sea
  • Arabian
  • Cocos
  • Scotia
• Types of Plate Boundaries


  • Divergent - form an ocean (magma chambers)
  • Convergent - mountains, vast land areas (continental and oceanic)
  • Transform - large faults (fracture zones)
• The Philippines is located in the Pacific Ring of Fire/circum-Pacific Belt, the largest active volcanic and earthquake region in the world
• The Philippines has active faults and trenches - Philippine Fault Zone (PFZ) 


  • Over 1,200 km long and runs from Luzon to Mindanao
  • Arc-parallel, left-lateral movement strike-slip fault divided to several segments
  • large-magnitude earthquakes in recent years -- earthquake (Ragay-Gulf)

  
• Active volcanoes in the Philippines


  • 24 active volcanoes, with 21 having historical eruptions, except for Cabalian, Leonard Kniaseff, and Isarog
• Plate movement rates in the Philippines range from ~6 mm/yr to ~9 mm/yr