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1. LESSON VI
ENVIRONMENTAL
HAZARDS

2. OBJECTIVE:
■ A. Natural Hazards
■ Earthquake
■ Forest fire
■ Tsunami
■ Hurricane/Cyclone/Typhoon
■ Flooding
■ Volcanic Eruption
■ B. Man-Made Hazards
■ Crime
■ War
■ Biological/Chemical
■ Threat

3. Natural Hazards
– are defined as environmental
phenomena that have the potential to
impact societies and the human
environment. These should not be
confused with other types of hazards,
such as manmade hazards.

4. • What causes a natural hazard?
– NATURAL DISASTERS, also referred to as natural hazards
are extreme, sudden events caused by environmental
factors such as storms, floods, droughts, fires, and heatwaves.
Natural disasters are now occurring with increasing severity,
scope and impact.
■ What are the 4 types of natural hazards?
– Natural hazards can be classified into several broad
categories: geological hazards, hydrological hazards,
meteorological hazards, and biological hazards.

5. Geological hazards
– are hazards driven by geological
(i.e., Earth) processes, in particular,
plate tectonics. This includes
earthquakes and volcanic eruptions.
In general, geological extreme
events are beyond human influence,
though humans have a large
influence on the impacts of the
events.

6. Meteorological hazards
– are hazards driven by meteorological (i.e.,
weather) processes, in particular those
related to temperature and wind. This
includes heat waves, cold waves, cyclones,
hurricanes, and freezing rain. Cyclones are
commonly called hurricanes in the Atlantic
and typhoons in the Pacific Ocean.

7. Hydrological hazards
– are hazards driven by hydrological (i.e., water)
processes. This includes floods, droughts,
mudslides, and tsunamis. Floods and droughts
can cause extensive damage to agriculture and
are among the main contributors to famine. The
deadliest natural disaster in world history (not
counting pandemics) was the 1931 Central
China floods, killing three or four million people.

8. Biological hazards
– are hazards driven by biological processes. This includes various
types of disease, including infectious diseases that spread from
person to person, threatening to infect large portions of the human
population. Many discussions of natural hazards exclude biological
hazards, placing them instead within the realm of medicine and
public health. If biological hazards are counted, then they include
the deadliest disasters in world history, including the Black Death
outbreak of bubonic plague in the 1300s, killing 75-100 million
people, and the 1918 "Spanish" flu pandemic, a global affair (the
name "Spanish" is due to historical coincidence) killing 50-100
million people.

9. Systems of Hazards
■ One extreme event can often be hazardous in several ways. For instance, an earthquake may destroy
buildings, cause landslides, and rupture sewer and water lines. The ruptured lines may, in turn,
contaminate water, causing water-borne diseases such as cholera. Indeed, a cholera outbreak
happened after the 2010 Haiti earthquake because of disruptions to clean water supplies.
■ Likewise, a single natural hazard can have many impacts. For instance, hurricanes involve high winds,
torrential rain, flooding, and storm surges. The winds may remove roofs and topple power lines. The
floods may inundate roads, homes and schools. Ecosystems can be damaged, threatening wildlife.
Some impacts can even be beneficial. A hurricane churns up ocean water, cooling surface water and
thus reducing the risk of another hurricane in the same area. Keeping track of these systems of
hazards and impacts is an important part of the study of hazards.

10. Who Studies Natural Hazards?
■ Contemporary research on natural hazard is interdisciplinary. Natural scientists study the nature
of the extreme events involved in hazards. Social scientists study the human dimensions of the
impacts and responses. Policy researchers, engineers, and ethicists study what can and should
be done to prepare for hazards and to respond to them when they occur. Some specific fields
active in natural hazards research include geography, medicine and public health, psychology,
economics, engineering, and sociology. Cartography and geographic information science are
increasingly important because these fields help analyze important spatial information about
hazards. Later in the module, we will see some examples of how cutting-edge information
technology is being used to revolutionize disaster response.

11. • EXAMPLE OF NATURAL HAZARD
■ EARTHQUAKE
An earthquake is a weak to violent shaking of the ground produced by the
sudden movement of rock materials below the earth's surface. The
earthquakes originate in tectonic plate boundary.

12. ■ FOREST FIRE
Wildfire, also called forest, bush or vegetation fire, can be described as any
uncontrolled and non-prescribed combustion or burning of plants in a natural
setting such as a forest, grassland, brush land or tundra, which consumes the
natural fuels and spreads based on environmental conditions (e.g., wind,
topography).
Forest fire is one of the most common disaster that takes place in many forest
systems throughout the globe. Forest fire has a devastating impact over the
environment, landscape, and ecological succession.

13. ■ TSUNAMI
– Tsunamis are giant waves caused by earthquakes or volcanic eruptions
under the sea. Out in the depths of the ocean, tsunami waves do not
dramatically increase in height. But as the waves travel inland, they build
up to higher and higher heights as the depth of the ocean decreases.