NATURAL DISASTERS

Hazard

- Natural process that is a threat to human life or property

Disaster

– Hazardous event that occurs over a limited time in defined area. Cost of natural disasters is increasing as pop increases – Criteria – one or more of the following:
• 10 or more people killed

• 100 or more people affected

• State of emergency is declared • International assistance is requested

Catastrophe
– Massive disaster that requires significant amount of money and/or time to recover.
Know the difference between a “hazard”and a “disaster” or “catastrophe”
Understand the basics of risk assessment
Recognize that natural hazards are generally high- 
energy events caused by natural Earth processes
Understand that the size of a hazardous event is 
inversely related to how often it occurs
Recognize that increasing human population and poor land-use changes compound the effects of natural hazards and can turn disasters into catastrophes

Disasters Are Now Becoming Catastrophes: Human Population Growth
World’s population has more than tripled in the past 70 years
Population grows exponentially
Increases exposure to hazards (location) and increases costs (development)

Approach to Natural Hazards
Identify location of hazard (where?) and size (how big?)
Determine recurrence interval and probability of event (how often?)
Estimate cost of event (how much?) and determine risk
Make a “forecast” or “prediction”
Observe/monitor any precursor activity and provide warning

Energy from ground – earthquakes, tsunami, volcanoes
Sun – Hurricane, flood
Gravity - landslides

Fundamental Concepts for Understanding Natural Processes as Hazards
Hazards are understandable from scientific evaluation.
Risk analysis is important.
Linkages exist between different natural hazards as well as between hazards and the physical environment.
Hazardous events that previously produced disasters are now producing catastrophes.
Consequences of hazards can be minimized.

EARTH MATERIALS – ELEMENTS, MINERALS, AND ROCKS

Neutrons: in nucleus, no charge, same mass as protons, Number of neutrons can change.
Isotopes: all have different atomic weights, some decay.
Rock: aggregate of one or more minerals. Classified according to how they form:
1) Igneous: crystallization/melting of magma (granite)
2) Sedimentary: Form from sediment from weathering shelstone (Shale)
3) Metamorphic: Pre-existing rock is changed by heat shale pressure, or fluids into a different rock (Slate)
Strong = Crystalline (Igneous, Metamorphic)
Weak = Clastic (sedimentary)

STRONG TO WEAK: GRANITE, SANDSTONE, SHALE

Minerals
Naturally organic
Inorganic crystalline solid
Defined chemical composition – can have different minerals with same chem. Compositon
Specific crystalline structure

Hard and strong: Quartz (harder than glass, doesn’t weather) Feldspar (as hard as glass, weathers slowly)

Soft and weak: Clay (soft, small platy grains) Calcite (precipitate, weathers easy)

Important Things To Know
Elements consist of protons, neutrons, and electrons
Isotopes of an element have the same number of 
protons but different numbers of neutrons
Definition of a mineral
Quartz and feldspar 
– Hard, strong silicate minerals 
– The primary constituents of the rock GRANITE
Clay 
– Weak silicate mineral that is found as very small platy particles 
– The primary constituent of the rock SHALE
Calcite (calcium carbonate) 
– Weak, soft, dissolves easily in weak acid (rainwater) – The primary constituent of limestone and marble

GEOLOGIC DATING AND THE GEOLOGIC TIME SCALE

Relative Age Dating
Sequence
Original horizontality
Sediment deposited in horizontal layers
Sedimentary rocks origin horizontally
Superposition
Oldest layer on bottom
Lateral continuity
Continue to side until interrupted Absolute Age Dating
Actual ages and dates, when provided with a specific YEAR
Numbers