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Summary Natural Hazards Glossary
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Natural Hazards – GlossaryChapter 1 – Introduction to Natural Hazards
Process: Thy physical, chemical, and biological ways by which events, such as volcanic
eruptions, earthquakes, landslides, and floods, affect earth’s surface.
Natural processes become hazardous when human beings live or work in their path.
Natural hazard: A natural process and event that is a potential threat to human life and
property. The process and events become hazardous because of human use
of land. No area is considered hazard-free. All natural hazards have the
potential to produce a catastrophe. Some have higher potential (floods,
hurricanes, earthquakes, volcanic eruptions, wildfires, tornadoes, and
heatwaves), other have smaller potential (coastal erosion, frost, lightning,
and expansive soils). Although it is possible to control some natural hazards
to a certain degree, many are completely beyond our control.
They are repetitive events, so study of their history is needed.
Disaster: A hazardous event that occurs over a limited time span within a defined area.
Criteria for a natural disaster are: 10+ people are killed, 100+ people are affected,
state of emergency is declared, and/or international assistance is required.
Catastrophe: A massive disaster that requires significant expenditure of money and a long time for
recovery to take place.
Mitigation: Reducing the effects of something. Term often used by scientists, planners and policy
makers. It is about combatting/stopping or limit something.
Adaptation: adjustment in natural or human systems in response to for example actual or
expected climatic stimuli or their effects, which moderates harm or exploits
beneficial opportunities.
Geologic cycle: Continuously operating processes (all together) that produce the earth materials,
land, water and atmosphere necessary for our survival. It includes the following
subcycles: tectonic cycle, rock cycle, hydrologic cycle & biochemical cycles.
Tectonic cycle: Large-scale geologic processes that deform the earth’s crust and produce landforms
such as ocean basins, continents, and mountains. Tectonic processes are driven by
forces deep within the earth. It involves creation, movement and destruction of
tectonic plates. It is responsible for the production and distribution of rock and
mineral resources invaluable to modern civilization, as well as hazards such as
volcanoes and earthquakes.
Tectonic plates: Large blocks of solid earth that give information about composition and
layering of the earth’s interior.
Rock cycle: The largest geologic subcycle and is linked to all other subcycles. It depends on
tectonic cycle for heat and energy, the biogeochemical cycle for minerals, and
hydrologic cycle for water.
Mineral: Naturally occurring, crystalline substance with defined properties.
Rocks: Aggregates of one or more minerals. They can vary greatly in their composition and
properties and can be classified into three general types.
Igneous rocks: Produced by the crystallization of molten rock. Can be found beneath and on earth
surface.
Sediment: A naturally occurring material that is broken down by processes
of weathering and erosion, and is subsequently transported by the action of wind,
water, or ice or by the force of gravity acting on the particles.
Lithification: Conversion to solid rock.
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,Deposition: The accumulation of sediment.
Sedimentary rock: Rock formed by lithification of accumulated layers of sediment.
Metamorphic rocks: Sedimentary rocks which are metamorphosed (altered in form), with deep
burial, by heat, pressure, or chemically active fluids. However, not all sources
of sediment have a biological or chemical origin and types of metamorphism
that do not involve deep burial.
Hydrologic cycle: Movement of water from the oceans to the atmosphere and back again.
Driven by solar energy, the cycle operates by way of evaporation,
precipitation, surface runoff, and sub-surface flow, and water is stored in
different compartments along the way.
Residence time: Estimated average amount of time that a drop of water spends in any one
compartment. This ranges from thousands of years (glacier) to nine days
(atmosphere).
Biogeochemical cycle: The transfer or cycling of a chemical element(s) through the atmosphere
(layer of gases surrounding the Earth), lithosphere (Earth’s rocky outer layer),
hydrosphere (oceans, lakes, rivers, and groundwater), and biosphere (part of
earth where life exists). It is intimately related to the other cycles. Rock and
hydrologic cycles are involved in many processes that transfer and store
chemical elements in water, soil and rock.
Biogeochemical cycles can most easily be described as the transfer of
chemical elements through a series of storage departments or reservoirs (air,
soil, groundwater, vegetation).
Flux: The rate of transfer.
Uniformitarianism: The idea that ‘the present is key to the past’. Events occur at the same rat
now as they have always done. Processes we observe today also operated in
the past. It does not demand or even suggest that the magnitude (amount of
energy expended) and frequency (how often a particular process occurs) of
natural processes remain constant with time. It refers to the invariance in the
principles underpinning science, such as the constancy of causality, or
causation, throughout time.
Environmental unity: One action causes others in a chain of actions and events. The air, the water,
the land, people, fauna, flora, earth’s solar neighbourhood and all activities
affect each and every other thing. Thus modifying and destabilizing the slope,
set off a chain or series of events that change the environment where people
live.
Prediction: Specifying the date, time and size of the event. Learning how to predict hazardous
events so we can minimize human loss and property damage is an important
endeavour.
Forecast: Predicting where or how often a particular event will occur. It has ranges of certainty.
The effects of a hazardous event can be reduced if we can forecast or predict it and if
we can issue a warning. Several elements are necessary: identifying the location,
determining the probability, observing any precursor events, forecasting or
predicting the event, and warning the public.
When a forecast of an event is issued, the certainty of the event is given, usually as
the percent change of something happening.
Precursor events: Events that preceded an hazardous event. Identification of them helps
scientists predict when and where a major event is likely to happen. For
example, the surface of the ground may creep (slowly move for a long
period) prior to an actual landslide. Rate of creep increases up to the final
failure and landslide. Volcanoes sometimes swell or bulge before an eruption,
often earthquake activity increases significantly in the area.
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,Warning: After a hazardous event has been predicted or forecast has been made, the public
must be warned. Flow of information leading to the warning of a possible disaster
should move along a predefined path. People do not always welcome such warnings.
Risk: The product of the probability of that event occurring times the consequences should
it occur.
Consequences: Damages to people, property, economic activity, public service, and so on. It can be
expressed on a variety of scales. A large event has a lower probability than a small
one, but its consequences are likely to be greater.
Acceptable risk: The level of human and property loss that can be tolerated by an individual,
household, group, organization, community, region, state, or nation.
Institutions approach it from an economic point of view, rather than from a
personal perception of the risk. On individual level, it is important to
recognize that you have some degree of choice regarding the level of risk you
are willing to live with. Individuals must learn to weight the pros and cons of
living in a given area and decide whether or not it is worth the risk.
A frequent problem of risk analysis is a lack of reliable data for analysing
either the probability or the consequences of an event. Similarly, it may be
difficult to determine the consequences of an event or series of events.
Linkages: Connection between natural processes that are hazardous to people. They fell into
two categories: hazards themselves are linked & natural hazards are linked to earth
material.
Carrying capacity: The maximum number of people the earth can hold without causing
environmental degradation that reduces the ability of the planet to support
the population.
Population momentum: is a typical consequence of the demographic transition. Even if a
high-fertility, high-growth population experiences an immediate drop
in fertility to replacement rate, that population will continue to grow
for several decades. Eventually, because the new fertility rate is
replacement, the population achieves equilibrium at some new level.
Population momentum is defined as the ratio of the size of the
population at that new equilibrium level to the size of the initial
population. Population momentum usually occurs in populations
that are growing.
Exponential growth: The population grows by the addition of a constant percentage of the current
population, nog by the addition of a constant number of people. It results in
higher population densities, more exposure of people to hazardous
processes, increased pollution, reduced availability of food and clean drinking
water, and a greater need for waste disposal and energy resources.
Magnitude: A function of the amount of energy released during a hazardous event.
Frequency: The interval between occurrences.
Impact: A function of the magnitude and the frequency.
Magnitude-frequency concept: The frequency of an event is inversely related to the
magnitude. Small earthquakes for example are more
common than large ones. Although planners need to be
prepared for large, devastating events, the majority of them
will be smaller.
Natural events with a moderate energy expenditure and
moderate frequency are often the most important shapers of
the landscape (the humans in the analogy example with
termites, humans and elephants).
Land-use may directly affect magnitude and frequency of
events.
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, Reactive: Following a disaster, we engage in search and rescue, firefighting, and providing
emergency food, water and shelter. The ways in which we deal with hazards are too
often primarily reactive.
Anticipate: This is needed to move to a higher level of hazard reduction. Land-use planning that
limits construction in hazardous locations, hazard-resistant construction, and hazard
modification or control are some adjustments that anticipate future disastrous
events and may reduce our vulnerability to them.
Direct effects: Include people killed, injured, dislocated or otherwise damaged by a particular event.
Are felt by fewer individuals.
Indirect effects: Responses to the disaster. Such as emotional distress, donation of money or
goods, and payment of taxes levied to finance the recovery. Affect more
people.
Stages of recovery from disaster: Emergency (damaged or destroyed) – restoration (patched,
return and function) – reconstruction I (rebuilt/replacement,
return at predisaster level or greater) – reconstruction II
(major construction, improved and developed).
Land-use planning: The process of regulating the use of land in an effort to promote more
desirable social and environmental as well as a more efficient use of
resources.
Natural service functions: Natural events, which take human life and destroy property, also
provide us with important benefits. Flooding causes erosion, but also
delivers sediment and flushes pollutants. Landslides may bring
benefits when debris forms dams. Volcanic eruptions create new land
and nutrient-rich volcanic ash may settle on existing soils and quickly
become incorporated, creating fertile soil. Earthquakes can provide
us with valuable services, since a fault gouge (an impervious clay
zone, formed by pulverized rocks during an earthquake) has formed
natural subsurface barriers, and most petroleum resources are
produced by deformation along faults that create large zones where
oil and gas accumulate.
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