Drought is a kind of natural disaster.
A natural disaster is an event with a natural, as opposed to human, cause that results in large-scale loss of life or property damage. It can be related to climate, geology, biology or even factors external to the Earth. Examples of this are earthquakes, hurricanes, droughts and floods. Disease epidemics are sometimes considered natural disasters, but they can be classified 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 quite regularly. Hurricanes, also known as cyclones, are among the most prominent natural disasters, occurring quite frequently in the hottest parts of the world. They start as areas of low pressure over warm oceans and grow into giant storms, hundreds of kilometers in diameter, that persist for several days. Their paths are quite predictable, which gives an alert for areas that are likely to be affected. Even so, they can cause substantial loss of life and millions of dollars in damage.
Many homes in New Orleans’ Ninth Ward were destroyed during Hurricane Katrina.
Tornadoes cover much smaller areas and can only last for a few minutes, but during that time they can cause devastation due to the extremely high wind speeds. In the worst tornado category, winds can reach 300 mph (482.8 km/h). That’s enough to completely destroy brick buildings and launch automobiles through the air. Fortunately, tornadoes of this severity are relatively rare.
An asteroid impact can destroy life on Earth.
Far less spectacular, but far deadlier, are droughts. Many people living in drier parts of the world tend to rely on seasonal rains for cultivation. From time to time, however, the rains do not arrive, due to fluctuations in the terrestrial climate. Prolonged lack of rain leads to crop failure, hunger and malnutrition, claiming millions of lives in some cases.
Volcanic eruptions are a type of natural disaster.
Excessive rainfall can cause flooding, which can result in large numbers of people losing their homes, crops being ruined, or rivers bursting their banks and causing death and destruction. Floods often result from the heavy rains that accompany hurricanes, compounding the damage. Intense and prolonged rains can also cause disastrous landslides and mudslides.
A natural disaster can include a biological threat.
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. While ancient fault lines can occasionally produce small earthquakes, the most destructive ones occur in geologically active areas, close to continental plate boundaries.
Tsunamis are usually triggered by powerful earthquakes on the ocean floor.
When an earthquake happens under the ocean, it can produce a tsunami, or a huge wave, that rapidly propagates away from its source. A tsunami can wreak massive destruction on coastlines hundreds of kilometers away. These huge waves can also be produced by landslides. There is concern that a future landslide on an unstable part of the island of La Palma in the Canary Islands could trigger a massive tsunami that would travel westward across the Atlantic, causing devastation on America’s east coast. This, however, is disputed by some geologists.
Locusts often form swarms that devour crops.
Volcanoes are related to earthquakes because they occur in geologically active zones around plate boundaries. In these areas, magma, under pressure, stays close to the surface and can erupt as lava. This can be of the “dripping” type, which flows 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 the pressure to build up until there is an explosive eruption.
A major flood is considered a natural disaster.
Many of the deaths and destruction from this type of natural disaster result from volcanic ash, which can fill the air, making breathing impossible, and build up on roofs, 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.
Catastrophic fires can result from natural disasters.
The biggest 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 off most of the human species, leaving behind only 1,000 – 10,000 breeding pairs. This phenomenon, called a population bottleneck, has been confirmed through genetic analysis.
Diseases and other Biological Threats
Natural disasters include severe thunderstorms.
Disasters that affect humans can be caused by other organisms. Historically, there have been a number of outbreaks of serious disease that have affected huge areas and claimed many lives. One such example was the “black death,” a form of bubonic plague that affected much of Europe during the Middle Ages and may have reduced the population by 30-60%.
High-magnitude earthquakes are a type of natural disaster.
The Spanish flu epidemic of 1918-1919 is thought to have killed about 50 million people — more than World War I, which had occurred just before. The threat to humans from the emergence of a new and lethal 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 famine.
Disaster from Space
Although there are no documented cases of human fatalities resulting from meteorites or asteroids, they do pose a threat. The risk of a major impact in the near future is considered to be very low, but looking further ahead, the probability is greater. The Earth has certainly experienced such events in the past, as evidenced by obvious craters in many parts of the world. In 1908, what is thought to be a large meteorite or comet fragment devastated a vast area of the Tunguska region of Siberia. Fortunately, the area was uninhabited and there were no known human casualties.
Natural and Human Factors
Some natural disasters result from a combination of natural and human factors. For example, the primary cause of a disease epidemic may be a natural microorganism, but its spread might 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 contributed in a major way to some famines. For example, bad agricultural policies are widely thought to have been at least partly to blame for the great famine of 1958-61 in China, during which 30 million people died.