2. Nevado del Ruiz, Colombia, 1985
• In 1845, the Colombian volcano erupted
and a mudflow killed approximately 1,000
people.
• Deposits from this event produced rich soil
in the Lagunilla River valley, enticing
people to move there and establish farms.
• The town of Aramero became the
agricultural centre for the valley and in 1985
had grown to a population of 23,000.
3. Nevado del Ruiz
• On November 13,
1985, a small
eruption of the
Colombian volcano
produced another
mudflow that buried
Aramero.
– 21,000 people death
– $200 million in
property damage
7. Nevado del Ruiz
• A review of the history of Nevado del Ruiz
shows that:
– The 1985 eruption and mudflows were
predicted, the hazard identified, and the risk
evaluated.
– Population growth since the last mudflow in
1845 greatly increased the number of people at
risk
– The tremendous loss of life could have been
significantly reduced if warnings had been
heeded.
8. Importance of studying natural
hazards
• The world can experience devastating
natural events like earthquakes, tsunamis,
volcanic eruptions, hurricanes, tornados,
etc.
• This events are the result of enormous
forces that are at work both inside and on
the surface of our planet.
• In this course we will study these forces,
how they interact with our civilization, and
how we can better adjust to their effects.
9. Internal and External Processes
• Process.- the physical, chemical, and
biological ways by which events such
as volcanic eruptions, earthquakes,
landslides, and floods, affect Earth’s
surface.
10. Internal Processes
• Some processes, such
as volcanic eruptions
and earthquakes, are
the result of internal
forces deep within
Earth.
• Most of these internal
processes are
explained by the theory
of plate tectonics.
11. External Processes
• Other processes associated with natural
hazards result from external forces that are
at or very near Earth’s surface.
• An example of these external processes is
the fact that the energy from the Sun
warms the Earth’s atmosphere and surface,
producing winds and evaporating water.
12. External Processes
• Wind circulation and water evaporation are
responsible for forming Earth’s climatic
zones and for driving the movement of
water in the hydrologic cycle.
• These external forces are in turn directly
related to hazardous processes, such as
violent storms and flooding, as well as
coastal erosion.
13. Internal and External Processes
• Therefore, hazardous processes result from
internal heating of Earth or from external
energy from the Sun.
• The energy released by natural processes
varies greatly. For example:
– the average tornado expends about 1,000
times as much energy as a lighting bolt,
– the volcanic eruption of Mount St. Helens in
May 1980 expended approximately 1,000,000
times as much energy as a lighting bolt.
14. Internal and External Processes
• Events such as earthquakes, volcanoes,
floods, and natural fires are natural
processes that have been occurring on
Earth’s surface since long before it was
populated by humans.
• These natural processes become
hazardous when human beings live or work
in their path.
15. Hazard, Risk, Disaster, and
Catastrophe
• A natural hazard is any natural process
that poses a threat to human life or
property.
– The event itself is not a hazard; rather, a
process becomes a hazard when it threatens
human interests.
16. Hazard, Risk, Disaster, and
Catastrophe
• Risk may be expressed as the probability
that a destructive event may occur
multiplied by the event’s likely impact on
people and property.
• Risk thus integrates hazard and social
vulnerability.
17. Hazard, Risk, Disaster, and
Catastrophe
•
• A natural disaster is the effect of a hazard
in society, usually as an event that occurs
over a limited time span in a defined
geographic area.
– The term disaster is used when the interaction
between humans and a natural process results
in significant property damage, injuries, or loss
of life.
18. Hazard, Risk, Disaster, and
Catastrophe
• A natural catastrophe, simply put, is a
massive disaster, requiring significant
expenditure of time and money for
recovery.
19. Major hazards in the USA
(not including blizzards and ice storms)
22. Death and damage caused by
natural hazards
• Natural hazards vary greatly in their
potential to cause a catastrophe.
– Floods, hurricanes, tornadoes, earthquakes,
volcanic eruptions, and large wildfires are the
hazards more likely to create a catastrophe.
– Landslides have only a moderate catastrophe
potential because they generally affect a small
area. Drought also has a moderate potential
because although it may cover a large area,
there is plenty of warning time before its worst
effects are felt.
– Hazards with low catastrophe potential include
coastal erosion, frost, and lightning.
24. Role of History in Understanding
Hazards
• A fundamental principle of understanding
hazards is that they are repetitive events.
• Knowledge of historic events and recent
geologic history of an area is vital to our
understanding and assessment of the
hazard.
• Linking the prehistoric and historic records
extends our perspective of time when we
study repetitive natural events.
25. Role of History in Understanding
Hazards
• To understand the nature and extent of a
natural hazard, we must study in detail its
historic occurrence as well as any geologic
features that it may produce or affect.
• Any prediction of the future occurrence and
effects of a hazard will be more accurate if
we can combine information about historic
and prehistoric behaviour with a knowledge
of present conditions and recent past
events, including land-use changes.
26. Geologic Cycle
• Geologic conditions and materials largely govern
the type, location, and intensity of natural
processes.
• Continuous processes produce the Earth’s
material, land, water and atmosphere, necessary
for our survival. These processes are referred to
as the geologic cycle, which is actually a group of
subcycles:
– The tectonic cycle
– The rock cycle
– The hydrologic cycle
– Biogeochemical cycles
41. Fundamental concepts for understanding
natural processes as hazards
1. Hazards can be predicted through scientific
analysis.
2. Risk analysis is an important element of
understanding the effects of hazardous
processes.
3. Linkages exist among different natural hazards
and between hazards and the physical
environment.
4. Damage from natural disasters is increasing.
5. Damage and loss of life from natural disasters
can be minimized.
42. 1. Hazards can be predicted
through scientific analysis
• Science and natural hazards
• Hazardous processes are natural
• Prediction and warning
44. Prediction and warning
• The effects of a hazardous event can be
reduced if it can be forecast and a warning
issued. This involve:
– Identifying the location of a hazard
– Determining the probability that an event of a
given magnitude will occur
– Identifying any precursor events, predicting the
event, and issuing a warning
46. 2. Risk analysis is an important
element of understanding the
effects of hazardous processes.
• The risk of a particular event is defined as
the product of the probability of that event
occurring times the consequences should it
occur.
• Determining acceptable risk is complicated.
47. 3. Linkages exist among different
natural hazards and between
hazards and the physical
environment.
• Linkages between natural process that are
hazardous to people generally fall into two
categories:
– Many hazards themselves are linked
– Natural hazards are linked to earth materials
48. 4. Damage from natural
disasters is increasing.
• Examples of disasters in densely populated
areas
• Human population growth
• Magnitude and frequency of hazardous
events
51. 5. Damage and loss of life from
natural disasters can be
minimized
• Reactive response: impact and recovery
from disasters.
– Direct and indirect effects
• Proactive response (Anticipatory response):
avoiding and adjusting to hazards
53. Proactive response (anticipatory)
• Proactive response: avoiding and adjusting
to hazards
– Land use planning
– Insurance
– Evacuation
– Disaster preparedness
– Artificial control of natural processes
56. Climate Change and Natural
Hazards
• There is strong evidence that on a global
scale Earth’s climate is now warmer than in
the previous 40 years since records began
• The 1990s appear to be the warmest
decade in the last 1,000 years
57. Climate Change and Natural
Hazards
• Mean sea level has risen by between 10 to
20 cm from 1860 to 2000.
• Snow cover has decreased by 10% since
the 1960s.
• Evidence of thawing of permafrost.
59. Climate Change and Natural
Hazards
• Extreme weather events such as drought,
floods, and storms are likely to become
more frequent and more intense in the
future.
• Since 1970s, El Niño events have
increased in frequency, magnitude and
duration.
61. Signals of Climate Change
• Global warming is projected to
increase both temperature and
rainfall at high latitudes and high
elevations.
• Migration of species
• Retreat of glaciers
• Rise of sea level
62. Potential health impacts of climate
change
• Problems associated with other global
changes:
– In 1997-1998, El Niño brought widespread
respiratory illnesses to Indonesia and Brazil
due to haze from uncontrolled forest fires.
– After hurricane Mitch in Central America
(1998), deforested areas experience flooding
and landslides, and the aftermath spawning
clusters of water-, insect- and rodent-borne
diseases (cholera, malaria, dengue fever, and
leptospirosis)
63. References
• Natural hazards: Earth's processes as hazards,
disasters, and catastrophes – Canadian Edition.
Keller, Edward A., Blodgett, Robert H., and
Clague John J. Pearson Prentice Hall, 2007.
• Dangerous Earth: An introduction to geological
hazards. Murck BW, Skinner BJ, and Porter SC.
John Wiley & Sons Inc. N.Y. 1997.
• Life support: the environment and human health.
Michael McCally. The MIT press. Cambridge,
2002.