Chapter 1: Introduction to Natural Hazards
2010 Haiti Earthquake: Lesson Learned
• Reasons this earthquake differed from previous earthquakes
1. Occurred in a heavily populated area – Port Au Prince – 3 Million
2. Poor construction of infrastructure in affected area – funds in Haiti used
primarily for food instead of disaster mitigation
• Lessons to be learned
o Design buildings to meet highest seismic standards
o Continue to provide adequate research funding to scientists
o Review and upgrade communication structure – quick response
o Public education programs on natural disasters
Hazardous Natural Processes And Energy Sources
• Process – the ways in which events (volcanoes, eruptions, earthquakes, landslides
and floods), driven by energy, affect the Earth’s surface.
• Energy is derived from three sources:
1. Earth’s Internal Heat – associated with earthquakes and volcanoes
2. Sun – associated with storms, floods, drought, coastal erosion
3. Gravitational Attraction of Earth – landslides, space objects
Hazard, Risk, Disaster, and Catastrophe
• Hazard – any natural process that threatens human life or property
• Risk – the probability that a particular destructive event will occur multiplied by
the event’s likely impact on people and property
• Catastrophe, Disaster – events that cause serious injury, loss of life, and property
damage over a limited time within a specified geographic area.
o Catastrophe is more massive than a disaster – have consequences far
beyond the area that is directly affected and require huge expeditions of
time and money to recover.
• Mitigation – when used by scientists, planners and policy makers refers to the
efforts to prepare for disasters and to minimize their harmful effects.
o United Nations designated the 1990s as the International Decade for
Natural Hazards Reduction. Objective was to minimized loss of life and
property damage from natural hazards however losses increased
• Acceptable Risk – What society is willing to take on
1.2 - Magnitude And Frequency of Hazardous Events
• Impact of a hazardous event is a function of its magnitude (amount of energy
released) and its frequency. • MagnitudeFrequency Concept – low frequency/high magnitude, high
frequency/low magnitude – inverse relationship.
o Approximated by exponential distribution – M=Fe^x where M is the
magnitude, F is the frequency, e is the natural logarithm, and x is a
1.3 - Role of Time in Understanding Hazards
• Natural disasters are recurrent events and thus study of past events provides
needed information for risk reduction.
• The nature of the event determines how far back the scientists must look (e.g.
meteors require studying greater historic data than earthquakes due to the
1.4 - Geologic Cycle
• Geology, topography, and climate govern the type, location and intensity of
• Geologic cycle:
o Tectonic Cycle
o Rock Cycle
o Hydrologic Cycle
o Biogeochemical Cycles
The Tectonic Cycle
• Tectonic – refers to the largescale geologic processes that deform Earth’s crust
and produce ocean basins, continents, and mountains.
• Tectonic Cycle – involves the creation, movement and destruction of tectonic
plates (the large blocks that form the outer shell of the Earth).
Earths Lithosphere and Crust
• Outermost (Surface) layer is the lithosphere – stronger than internal. Upper part is
the crust (oceanic or continental)
• Below the lithosphere is the asthenosphere – hot layer of lowstrength rock
Types of Plate Boundaries
• Plate Tectonics – Process associated with the origin, movement, and destruction
of tectonic plates.
• Divergent Boundaries – occurs where two plates move away from one another
and a new lithosphere is created.
o Occur in large underwater ridges (midocean ridges), through a process
known as seafloor spreading.
• Convergent Boundaries – occur where two plates collide headon. Oceanic plate
is drawn down beneath a continental plate through a process called subduction.
These areas are called subduction zones.
• Transform Boundaries – occur where two plates slide horizontally past one
another and form a transform fault.
• Hot Spots – volcanoes occur within lithospheric plates The Rock Cycle
• Rocks aggregates of one or more minerals
• Minerals naturally occurring, crystalline substance with a specific elemental
composition and a narrow range of physical properties.
• Three general groups of rocks
o Igneous – crystallization of molten rock beneath and on the Earth’s surface
o Sedimentary – Broken down chemical rock by weathering to form
particles called sediment. Sediment is deposited and then converted and
compacted into solid rock (lithification).
o Metamorphic – sedimentary rock may have deep burial, heat, pressure,
and chemically active fluids through metamorphosis.
• Cycle is linked to all other cycles.
The Hydrologic Cycle
• Hydrologic Cycle – cycling of water from the oceans to the atmosphere, to
continents and islands, and back again to oceans.
• Residence Time – amount of time a drop of water spends in any one compartment.
• Biogeochemical Cycle – the transfer or cycling of an element through the
atmosphere (layer of gases surrounding Earth), lithosphere (Earth’s rocky layer),
hydrosphere (oceans, lakes, glaciers, rivers and groundwater), and biosphere
• Cycle is intimately related to rock, hydrologic, and tectonic.
1.5 – Fundamental Concepts For Understanding Natural
Processes as Hazards
1. Hazards Can Be Understood Through Scientific Investigation And
Science and Natural Hazards
• Use of the scientific method to better understand natural hazards – past history of
similar events, patterns, precursor events
• Scientific Method – Formulate a question and test hypothesis’
Hazardous Processes Are Natural
• Although we can control some hazards to a certain degree, most are beyond our
• The best approach to hazard reduction – identify hazardous processes and
delineate the geographic areas where they occur. Avoid putting people and
property in harms way. Prediction, Forecast and Warning
• Prediction – specifying the date and size of an event
• Forecast – Announcem