Natural Hazard and Natural Disaster

What is a Natural Hazard? Natural hazards are naturally occurring physical phenomena caused either by rapid or slow onset events which can be geophysical (earthquakes, landslides, tsunamis and volcanic activity), hydrological (avalanches and floods), climatological (extreme temperatures, drought and wildfires), meteorological (cyclones and storms/wave surges) or biological (disease epidemics and insect/animal plagues).

What is a Natural Disaster? A disaster is a sudden, calamitous event that seriously disrupts the functioning of a community or society and causes human, material, and economic or environmental losses that exceed the community’s or society’s ability to cope using its own resources. Though often caused by nature, disasters can have human origins. (International Federation of Red Cross and Red Crescent Societies)

SIMILARITIES geographical occurences natural events threatens lives, property and environment not man made

DIFFERENCES Natural Hazard -relate to the physical characteristics of an area; more localized -tends to occur repeatedly in the same geographical location Natural Disaster -knows no boundaries on the areas where they occur; damage can spread -happens when the effects of a natural hazard causes serious problems for people they affect

Natural Hazard In economics, it is thought as a threat – it doesn’t mean that it will happen Natural Disaster a consequence, an effect - economic - social serious damage - property - environment

Concepts of Natural Hazards Volcanoes Earthquakes Landslides Mud Flows Tsunamis Physical Geography

Volcano

In June 1991, after more than four centuries of slumber, Pinatubo Volcano in the Philippines erupted so violently that more than 5 billion cubic meters of ash and pyroclastic debris were ejected from its fiery bowels producing eruption columns 18 kilometers wide at the base and heights reaching up to 30 kilometers above the volcano’s vent. In its wake 847 people lay dead, 184 injured, 23 missing, and more than 1 millon people displaced. Hundreds of millions of dollars in private properties and infrastructure lay in ruins which would require tens of billions of pesos and several years to rebuild. For months, the ejected volcanic materials remained suspended in the atmosphere where the winds dispersed them to envelope the earth, reaching as far as Russia and North America. This phenomenon caused the world’s temperature to fall by an average of 1 degree Celsius. Clearly, Pinatubo’s eruption signals the world’s most violent and destructive volcanic event of the 20th century.

Pinatubo unleashed three major destructive agents, namely: ashfall, pyroclastic flow and lahar that caused destruction to Central Luzon's infrastructure and rendered its vast agricultural lands into virtual wastelands. Hardest hit were the provinces of Zambales, Pampanga, and Tarlac where more than 6,000 hectares of agricultural lands and fishponds were affected by ashfalls and lahars.

Types of Plate Boundaries

Destructive Margins (Convergent)

Conservative margins (Transform) At conservative margins mountains are not made, volcanic eruptions do not happen and crust is not destroyed. Instead, 2 plats either slide past each other in opposite directions, or 2 plates slide past each other at different speeds. As they move past each other friction builds as the plates snag and grind on one another. When this friction is eventually released it sends shock waves through the earth’s crust. We know these shock waves as earthquakes, and a good example of this is the San Andreas fault in California, where the Pacific plate is moving NW at a faster rate than the North American plate.