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Chapter 1: Natural Hazards and Disasters
Natural Hazards Third Edition Keller/DeVecchio © 2012, 2009, 2006 by Pearson Education, Inc.
Terms in this set (39)
A natural process and event that is a potential threat to human life and property. The process and the events themselves are not a hazard, but become so because of human use of the land.
A hazardous event that occurs over a limited time span within a defined geographic area. Criteria for a natural disaster are 1) 10 or more people are killed, 2) 100 or more people are affected, 3) a state of emergency is declared, and 4) international assistance is requested. If any one of these applies, an event is considered a NATURAL DISASTER.
A situation in which damages to people, property or society are sufficient that recovery or rehabilitation is a long, involved process. Often requires a significant expenditure of money and years for recovery to take place.
Events most likely to result in a catastrophe: Floods, hurricanes, tornadoes, earthquakes, volcanoes, large wildfires.
Less likely: Drought, coastal erosion, lightning, etc.
Concentrations of populations and resources in areas of natural hazards increase the impact of these hazards.
To reduce the effects of something - often used by scientists, planners, and policy makers in describing disaster preparedness efforts (after floods, water supplies may be contaminated; to mitigate the contamination, a relief agency/government may distribute bottled water)
Continuously operating processes producing the earth materials, land, water, and atmosphere necessary for our survival. Collectively, these processes are referred to as the Geologic Cycle, which is really a group of subcycles that includes:
* the tectonic cycle
* the rock cycle
* the hydrologic cycle
* the biogeochemical cycles
Tectonic & Tectonic Cycle (i)
The large-scale geologic processes that deform Earth's crust and produce land forms such as ocean basins, continents, and mountains. The Tectonic Cycle involves the creation, movement and destruction of the lithospheric plates. It is responsible for the production & distribution of rock & mineral resources invaluable to modern civilization, as well as hazards such as volcanoes & earthquakes.
Rocks & Rock Cycle (i)
Aggregates of one or more minerals. The rock cycle is the LARGEST of the geologic subcycles (tectonic, rock, hydrologic, biogeochemical), and is linked to all the other subcycles. It depends on the tectonic cycle for heat and energy, the biogeochemical cycle for materials, and the hydrologic cycle for water. It may be considered a worldwide earth material recycling process driven by Earth's internal heat, which melts the rocks subducted in the tectonic cycle.
There are 3 major rock types, according to how they have been formed in the rock cycle: Igneous, Sedimentary, and Metamorphic.
Igneous Rocks (i)
Formed from crystallization of magma (molten rock) beneath AND ON Earth's surface.
Rocks at or near the Earth's surface break down chemically and physically by weathering to form particles that vary in size from fine clay to boulder-sized gravel. Sediment formed by weathering is then transported by wind, water, ice, and gravity to depositional basins, such as the ocean.
When sediment formed by weathering is transported by wind/water/ice/gravity to depositional basins, such as the ocean, and those materials slow down, the sediment settles and accumulates by a process known as deposition.
Accumulated layers of sediment that have gone through the process of deposition eventually go through lithification, which is the conversion to solid rock, resulting in sedimentary rocks.
Sedimentary Rocks (i)
Following deposition of sediment into a basin, lithification converts that sediment into a sedimentary rock. With deep burial, sedimentary rocks may be metamorphosed by heat/pressure/chemical fluids to produce metamorphic rocks.
Metamorphic Rocks (i)
Sedimentary rocks that have become deeply buried may become metamorphosed (altered in form) by heat, pressure, or chemically active fluids to produce metamorphic rocks. Metamorphic rocks may be buried to depths where pressure and temperature conditions cause them to melt, beginning the entire rock cycle again.
Hydrologic Cycle (i)
The movement of water from the oceans to the atmosphere and back again. Driven by solar energy. Operates by way of evaporation, precipitation, surface runoff, and subsurface flow, and water is stored in "compartments" (oceans, atmosphere, rivers, streams, groundwater, lakes, ice caps, glaciers) along the way.
Residence Time (i)
Estimated average amount of time that a drop of water spends in any one compartment (see: hydrologic cycle), ranges from tens of thousands of years or more in glaciers to nine days in the atmosphere.
Biogeochemical Cycle (i)
The transfer or cycling of a chemical element (or elements) through the atmosphere (the layer of gases surrounding the earth), lithosphere (Earth's rocky outer layer), hydrosphere (oceans, lakes, rivers, and groundwater), and biosphere (the part of the Earth where life exists).Most easily described as the transfer of chemical elements through a series of storage compartments or reservoirs (e.g. air, soil, groundwater, vegetation). For example, carbon (in the form of CO2) is exhaled by animals, enters the atmosphere, and is then taken up by plants.
Risk Analysis (i)
Estimates the probability that an event will occur, and the consequences resulting from that event.
"The present is the key to the past" popularized in 1785 by James Hutton (referred by some as the father of geology). Holds that processes we observe today also operated in the past (flow of water in rivers, formation & movement of glaciers, landslides, waves on beaches, uplift of the land from earthquakes, etc.)
Uniformitarianism DOES NOT suggest that the magnitude (amount of energy expended) or frequency (how often a particular process occurs) of natural processes remain constant with time.
Currently, the present is the key to the future - when environmental geologists examine recent landslide deposits in an area designated to become a housing development, they must use uniformitarianism to infer where there will be future landslides, as well as predict what effects urbanization will have on the magnitude & frequency of future landslides.
The principle states that one action often leads to others in a sequence (or chain) of actions and events (you can't do just one thing). For example, if we remove native vegetation from a steep slope, a landslide may occur; the slide may dam a stream, which will back up, forming a lake.
Specifying the date, time, and size of a hazardous event.
Future activity can be predicted from frequency of past events, patterns of occurrence, and precursor events.
Providing a range of certainty (generally as a percentage chance) that an event will arrive at a particular location, such as a 40% chance of rain.
Precursor Events (i)
Small events leading up to a larger hazardous event, such as the surface of the ground creeping prior to a landslide, or volcanoes bulging before an eruption
Alerting the public when a hazardous event has been predicted or a forecast has been made. For some events, there is insufficient data to predict or forecast events accurately.
Public not always thrilled, sometimes event doesn't happen, fatigue.
Risk / Risk Assessment
The product of the probability of a particular event occurring multiplied by the consequences should that event occur. Risk analysis estimates probability and consequences. For example, if we are considering the risk of earthquake damage to a nuclear reactor, we may evaluate the consequences in terms of radiation released.
If we know both: the probability of the event occurring AND the possibility consequences of an event occurring at a particular location, THEN we can assess the risk posed to people and property, EVEN if we can't accurately predict WHEN the hazard will next occur.
1. Critical Mapping and Analysis
2. Economic Impact Analysis
3. Societal Impact Analysis
4. Total Environmental Impact Analysis
Acceptable Risk (i)
The risk that society or individuals are willing to endure. On an individual level, there is some degree of choice regarding the level of risk that individual is willing to live with.
Decisions humans make (or risks they decide to take) before, during, and after a hazardous event can greatly increase or decrease the consequences of a natural hazard event.
First, many hazards are linked to other hazards (hurricanes cause flooding and erosion; volcanic eruptions cause mudflows and floods, and eruptions in the ocean cause tsunamis).
Second, natural hazards are linked to earth materials (exposures of weak rocks i.e. shale = landslides; strong rocks that are fractured i.e. granite = rockslides)
Carrying Capacity (i)
The maximum number of people Earth can hold without causing environmental degradation that reduced the ability of the planet to support the population.
Population Momentum (i)
More people are living longer as a result of improved sanitation, nourishment, water quality, and medicine. Twice as many people are born than die.
Exponential Growth (i)
The population does not grow each year by the addition of a constant NUMBER of people; rather, it grows by the addition of a constant percentage of the current population (population "bomb"). More people = greater exposure to hazards. Education (of women) is hugely important (literacy).
Magnitude = The amount of energy released
Frequency = The interval between occurrences
The concept is that the frequency of an event is INVERSELY related to the magnitude. Small events happen more frequently, and large events happen less frequently. This is due to increasing human population, poor land-use practices, and global climate change.
Reactive / Anticipatory (i)
Reactive = Following a disaster, we engage in search & rescue, firefighting, and providing emergency food, water & shelter.
Anticipatory = Land-use planning that limits construction in hazardous locations, hazard-resistant construction, hazard modification or control, proactive disaster preparedness, education of the public, and adjustments that anticipate future disastrous events and reduce our vulnerability to them.
Direct Effects / Indirect Effects (i)
Direct Effects = People killed, injured, dislocated, or otherwise impacted by a hazardous event. Felt by fewer individuals.
Indirect effects = General community responses to a disaster; emotional distress, donations of money or goods, payment of taxes levied to finance the recovery. Affect/felt by many more people.
People can avoid building on floodplains, in areas where there are active landslides, and in places where coastal erosion is likely to occur.
Artificial Control of Natural Processes (i)
Attempts to control landslides, floods, and lava flows have had mixed success. Seawalls constructed to control coastal erosion may protect property to some extent, but over a period of decades, they tend to narrow or even eliminate the beach. Common methods of flood control are channelization and construction of dams and levees.
Five Fundamental Concepts
1. Hazards are predictable [Science helps us predict hazards on the basis of frequency of past events, patterns in their occurrence, and types of precursor events.]
2. Risk analysis aids understanding of hazards [Knowing hazard risks can help people make decisions.]
3. Natural hazards are linked to other hazards and the physical environment
4. Natural hazards that used to caused disasters are now causing catastrophes due to increasing population and poor land-use practices.
5. Consequences of hazards can be minimized [through scientific understanding, land-use planning & regulation, engineering, and proactive disaster preparedness.]
Professor Robert Bea, UC Berkeley
Has pointed out that 20% of the financial losses in a disaster may be directly related to the event itself, but the majority of the cost of catastrophes could be greatly reduced by improving human systems that include warnings and better understanding of the hazard.
He notes that often people and institutions take the easy road, putting maintenance or solving a problem of a critical area on the back burner until an event happens, and then everyone acts really surprised.
Natural Service Functions (i)
The same natural events that we consider disasters also provide important benefits (e.g. flooding of the Mississippi brings nutrients to the floodplain so soils are good for agriculture; landslides that form dams may create lakes in mountainous areas for valuable water storage; volcanic eruptions can create new land such as the Hawaiian Islands; volcanic ash is nutrient rich and may make soil suitable for crops after ash settles upon it).
Global Climate Change / Warming
Global warming will likely affect the frequency and intensity of thunderstorms and tornadoes, and the intensity of hurricanes.
Rising sea level will increase coastal erosion.
With global warming, deserts and semiarid regions will expand, and droughts will be more common.
With warming, the frequency and intensity of wildfire will both likely increase.
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