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LIVING WITH DISASTER
LIVING WITH DISASTERS
Open Geography Education by R. Adam Dastrup is licensed under a Creative Commons Attribution 4.0 International License.
LIVING WITH DISASTERS
SCIENCE BEHIND NATURAL HAZARDS
Because of the scientific method, we understand why most natural disasters occur and where. For example, because of the theory of plate tectonics, we know understand why nearly 90 percent of all natural disasters occur in the Pacific Ocean called the Ring of Fire. That same theory has helped to explain why some volcanoes are more explosive than others. We also understand that different tectonic plate boundaries produce different fault lines and thus different types of earthquakes.
Natural hazards also have seasons - especially those controlled by external forces. The United States has more tornadoes than the rest of the world combined and mostly occur in the spring. Landslides are also most prone in the spring when snow begins to melt and over-saturate the ground. Wildfires are common in the middle of summer when the land is dry and thunderstorms tend to produce lightning without any precipitation. And hurricanes tend to peak in late August and into September when the ocean is warmest.
Since hazards are predictable in some manner, it becomes important to develop some kind of warning system. Predictions, such as weather predictions, state that it will occur at a specified time, date, and intensity. It is like saying a major snowstorm will reach Salt Lake City at 4:30 PM for the commute home. Now a forecast is slightly different. A forecast states a probability of something occurring; such as a 40 percent of showers today. Forecasts are much more broad than predictions.
One final note I'd like to discuss is the difference between a watch and a warning. A watch is issued when the conditions for a particular event are right. So if a thunderstorm is strong enough and rotating, it is possible that a tornado may form. Or if an earthquake with a magnitude of 7.5 strikes somewhere in the ocean, a tsunami watch may be issued because the earthquake was strong enough to create one. But a watch does not mean that it will occur. But is a tornado is spotted on the ground or a ocean sensor records an approaching tsunami, then a warning is sent out to the areas that could be impacted.
NATURAL HAZARDS ARE CONNECTED
In order to understand how to prepare for a natural hazard, a risk assessment must be conducted. The risk of a potential hazard is defined as "the product of the probability of that that event occurring times the consequence should it occur."
HAZARDS, DISASTERS, AND CATASTROPHES
In the summer of 2008, China was rocked by a magnitude 8.0 earthquake that killed over 80,000 people. A week earlier a cyclone struck Burma killing 130,000. On January 12, 2010 a magnitude 7.0 earthquake killed nearly 300,000 people and leveled the capital city of Port-a-Prince. On March 11, 2011 a magnitude 9.0 earthquake generated a tsunami off the coast of eastern Japan killing 30,000 people. Are natural disasters getting worse? Not really, humans are overpopulating the place. Over the last 70 years, the world's population has tripled to 6.7 billion. It is expected by exponentially grow and by 2050 the world's population will reach 9 billion. Exponential growth means the world's population will not grow linearly (in a straight line), but rather as a percent. Our increased population size has caused air quality to suffer, reduced the availability of clean drinking water, increased the world's extreme poverty rate, and has made us more prone to natural hazards.
There is also a relationship between the magnitude of an event (energy released) and its frequency (intervals between episodes). The more earthquakes that occur for a particular location, the weaker they tend to be. That is because built-up energy is slowly being released at a fairly constant rate. But if their are long intervals between one earthquake and the next, the energy can build and can ultimately produce a stronger earthquake. That is the problem with earthquakes along the Wasatch Front of Utah. The interval or frequency between earthquakes tends to be 1,500 years, so the magnitude tends to be high because of the built-up energy. At some point we are going to want to get this earthquake over with because the longer it waits the worse it will be.
Now there are two types of effects caused by natural disasters: direct and indirect. Direct effects, also called primary effects, include destroyed infrastructure and buildings, injuries, separated families, and even death. Indirect, sometimes called secondary effects, are things like contaminated water, disease, and financial loses. In other words, indirect effects are things that happen after the disaster has occurred.
How we chose to build our cities will greatly determine how many lives are saved in a disaster. For example, we should not be building homes in areas that are prone to landslides, liquefaction, or flash floods. Rather these places should be left as open-space such as parks, golf courses, or nature preserves. This this is a matter of proper zoning laws which is controlled by local government. Other ways we can reduce the impact of natural disasters is by having evacuation routes, disaster preparedness and education, and building codes so that our building do not collapse on people.
So what is the difference between a natural hazard, a disaster, or a catastrophe? Using direct quotes from page 6 of the textbook, the author defines each as follows:
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