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Natural disasters, such as hurricanes, tornadoes, droughts, floods, earthquakes, tsunamis, volcanoes, and disease outbreaks, can cause large-scale loss of life and property damage. Some disasters, like locust swarms and meteorite impacts, are caused by biological or space factors. Human activities can also contribute to disasters, such as poor agricultural policies leading to famines.
A natural disaster is an event with a natural cause, contrary to man’s, that results in large-scale loss of life or damage to property. It could be related to weather, geology, biology, or even factors off Earth. Examples are earthquakes, hurricanes, droughts and floods. Disease outbreaks are sometimes considered natural disasters, but they can be placed in a different category. In some cases, natural and human factors can combine to produce a disaster.
Weather and climate
The planet’s climate produces disasters on a fairly regular basis. Hurricanes, also known as cyclones, are among the most important natural disasters, occurring quite frequently in warmer parts of the world. They start as areas of low pressure over warm oceans and grow into giant storms, hundreds of miles in diameter, that persist for several days. Their paths are quite predictable, which provides advance warning to areas that may be affected. Even so, they can cause significant loss of life and millions of dollars in damage.
Tornadoes cover much smaller areas and may only last a few minutes, but they can cause devastation during that time, due to extremely high wind speeds. In the worst tornado category, winds can reach 300 mph (482.8 km/h). This is enough to completely destroy brick buildings and throw cars into the air. Fortunately, tornadoes of this severity are relatively rare.
Far less spectacular, but far more deadly, are droughts. Many people who live in drier parts of the world often rely on seasonal rains to grow crops. From time to time, however, the rains do not come, due to fluctuations in the earth’s climate. Prolonged lack of rainfall leads to crop failure, starvation and malnutrition, in some cases claiming millions of lives.
Excessive rainfall can cause flooding, which can cause large numbers of people to lose their homes, ruin crops, or burst river banks causing death and destruction. Flooding often results from the heavy rains that accompany hurricanes, compounding the damage. Prolonged heavy rains can also cause disastrous landslides and mudslides.
Geological disasters
Earthquakes are among the most destructive natural disasters. They occur at or near fault lines – cracks in the earth’s crust that mark the boundary between two different sections. When these sections move relative to each other, the resulting vibration produces an earthquake. Although old fault lines may occasionally produce small earthquakes, the most destructive ones occur in geologically active areas, near continental plate boundaries.
When an earthquake occurs under the ocean, it can produce a tsunami, or huge wave, that travels rapidly outward from its source. A tsunami can cause massive destruction to coastlines hundreds of miles away. These huge waves can also be produced by landslides. There are fears that a future massive landslide on an unstable part of the island of La Palma in the Canary Islands could trigger a massive tsunami that would travel west across the Atlantic, wreaking havoc on America’s east coast. This is, however, disputed by some geologists.
Volcanoes are related to earthquakes in that they occur in geologically active zones around plate boundaries. In these areas the magma, under pressure, is close to the surface and can erupt as lava. This can be of the “runny” type, which comes out relatively quietly and follows well-defined channels. Alternatively it can be of the “sticky” type; this can solidify at the top of a volcano, causing pressure to build up until an explosive eruption occurs.
Much of the death and destruction from this type of natural disaster comes from volcanic ash, which can fill the air, making breathing impossible, and accumulate on rooftops, causing buildings to collapse under the weight. Pyroclastic flow is another major hazard associated with some volcanic eruptions. This consists of a mixture of hot gas, ash and rock fragments rushing at high speed from the source of the eruption and destroying everything in its path.
The largest known volcanic natural disaster may have occurred in prehistoric times. Some scientists believe that the eruption of Mt. Toba in Indonesia over 73,000 years ago may have killed most of the human species, leaving only 1,000 – 10,000 breeding pairs. This phenomenon, called a population bottleneck, has been confirmed through genetic analysis.
Diseases and other biological threats
Disasters that affect humans can be caused by other organisms. Historically, there have been numerous outbreaks of serious disease affecting large areas and claiming many lives. One example was the “Black Death”, a form of bubonic plague which affected much of Europe during the Middle Ages and may have reduced the population by 30-60%.
The Spanish flu epidemic of 1918-1919 is thought to have killed an estimated 50 million people, more than World War I, which happened shortly before. The threat to humans from the emergence of a lethal new strain of the influenza virus remains. Organisms that do not cause disease can occasionally cause disasters. Locusts, for example, can form huge swarms that can devour many acres of crops in a very short time, sometimes causing famines.
Disaster from space
While there are no documented cases of human fatalities resulting from meteorites or asteroids, they pose a threat. The risk of a major impact in the near future is considered very low, but looking further ahead the probability is higher. The Earth has certainly experienced such events in the past, as evidenced by evident craters in many parts of the world. In 1908, what is thought to be a large meteorite or comet fragment devastated a large area of the Tunguska region of Siberia. Fortunately, the area was uninhabited and there were no known human fatalities.
natural and human factors
Some natural disasters result from a combination of natural and human factors. For example, the root cause of a disease outbreak may be a naturally occurring microorganism, but its spread may be encouraged by human behavior and activities, such as living in close proximity to infected animals or rapid international travel. Human activities may also have been major contributors to some famines. For example, poor agricultural policies are believed to have been at least partially responsible for the Great Famine of 1958-61 in China, during which 30 million people died.
