Natural disasters disrupt the normal functioning of natural processes adversely affecting the existence of life on earth. Widespread floods, earthquakes, tornadoes and hurricanes can cause the mass destruction of both living and non-living things. The affected surface is damaged beyond recovery leaving the surface affected scarred forever. An estimate of about 905 calamities has been reported worldwide in 2012.
Given below is a list of the top ten natural calamities that scar the earth’s surface:
Hurricanes are characterized by strong winds and thunderstorms that can produce heavy rains. They normally occur over large bodies of warm water. In addition to the strong winds and heavy rains caused by a hurricane, they also generate high waves and tornadoes, thereby posing a great threat to the coastal regions. Hurricane Franklin that occurred in the North Atlantic Hurricane basin is an example of a strongly sheared tropical cyclone. The heavy rains can even create floods which also adversely affect the human population. Most hurricanes happen during the late summer when the difference between the land and sea surface temperature is at its peak.
The rapid release of energy from the earth’s crust creating seismic waves is responsible for an earthquake, also known as a quake or a tremor. The magnitude of an earthquake is measured using a seismometer. The 9.0 magnitude earthquake that struck Japan in 2011 is the largest among the recent reported tremors. An estimate of around 500,000 earthquakes occurs every year of which about 100,000 can be felt. While the earth’s tectonic plates are responsible for most earthquakes, certain human activities can also trigger a temblor. Drilling and injecting liquid into wells, coal mining and oil mining are some of them. The 2004 Indian Ocean earthquake of magnitude 9.1-9.3 is the third largest earthquake that struck the world.
Tornadoes are violently rotating columns of air that are also referred to as twisters or cyclones. They often look like a funnel suspended from the clouds. A typical tornado takes the shape of a condensation funnel and has a wind speed of less than 110 miles per hour. Tornadoes occur frequently in tropical areas that lie close to the equator and are less common in high latitudes. The Enhanced Fujita scale (previously called the Fujita scale) is used to calculate the amount of damage caused by a tornado. Antarctica is the only continent that has never been affected by a tornado.
4. Volcanic Eruption
The expulsion of lava, tephra and other gases from a volcanic vent or fissure is termed as a volcanic eruption. Volcanologists have briefly classified the eruptions into three types- magmatic, which involves and outward propulsion from the magma due to the decompression of gases, phreatomagmatic which happen in a manner that is exactly opposite to that of a magmatic eruption and phreatic which is caused by the super heating of steam within the magma. The eruptive strength is measured using a Volcanic Explosivity Index, a magnitude scale ranging from 0 to 8.The different types of eruptions are named after famous volcanoes where a similar characteristic has been exhibited.
A tsunami also known as a harbour wave is a series of water waves caused by the displacement of a large water body like an ocean or a sea. Underwater explosions, volcanic eruptions, earthquakes or landslides that happen under the earth’s surface can trigger a tsunami. Thucydides a Greek philosopher of the 5th century BC claims that a tsunami is caused by a submarine earthquake. However the exact nature of a tsunami remains unclear even today. In appearance, the tsunami wave resembles a rapidly rising tide and is hence often referred to as a tidal wave. They occur in a ‘wave train’ at periodic intervals ranging from minutes to hours. Though warning systems are established in prone areas, a tsunami cannot be precisely predicted even if the magnitude and location of an earthquake is known.
A flood can submerge a normally dry land in water and is a threat to the existence of life on earth. Flooding may occur due to an overflow of water from a river or a lake or due to an accumulation of rainwater on a saturated ground. It usually happens in flat or low-lying areas where the accumulation of water is high. It can also occur when the rate of flow of water exceeds the capacity of a water channel. In October 2005, when the river bodies of north western Bangladesh exceeded their maximum capacity, dozens of villages were inundated. While a flood normally develops in a slow pace, flash floods occur in the twinkling of an eye with no accompaniment of the rains. This can wreck havoc in large scale damaging both vegetative and non-vegetative resources.
A wildfire also referred to as brushfire, forest fire, grass fire or a hill fire normally occurs in the countryside or a wilderness area. It can be best described as an uncontrolled fire that causes a mass destruction of combustible vegetation. They frequently occur in regions that are sufficiently moist to allow the growth of vegetation but have extended hot or dry periods. The generally hot and dry climate of Australia makes the country vulnerable to random wildfires during summer and spring. Wildfires are a huge threat to life and infrastructure. The four primary causes of a wildfire are volcanic eruptions, lightening, sparks from rockfalls and spontaneous combustion. The charred landscape of North Cascades, U.S is an example.
A shortage of water supply that lasts for months or years in a particular region is called a drought. Droughts generally occur in regions that consistently receive below average precipitations. It can adversely affect the ecosystem and agriculture of the affected region. Droughts are of three types- Meteorological, Agricultural and Hydrological. Long term droughts can result in the creation of arid biomes like deserts and grasslands. Dry earth formed in the Sonoran desert of Mexico is an example. Dust storms, erosions, diminished supply of crops and other resources, wildlife extinction etc are some of the common consequences of drought.
Also known as a snow-slide or a snow-slip, the avalanche is the rapid flow of snow down a sloping surface. Avalanches are usually initiated from a mechanical failure in the snow pack (slab avalanche) and grow in speed, mass and volume as it flows down. Large avalanches have the strength to entrain not just ice packs but also rocks, trees and other materials that come its way. Mostly, avalanches occur during storms under increased load due to snowfalls. Ice-falls, rockfalls, rain and earthquakes are some of the natural factors that trigger an avalanche. An estimate of about 40,000 to 80,000 soldiers lost their lives due to a series of avalanches in the Alps during World War 1.
Rockfalls, deep failure of slopes and shallow debris flows that occur in offshore, onshore and coastal environments are the main causes that lead to a landslide. A landslip is a geographical phenomenon that occurs when the stability of a slope shifts from a stable to an unstable condition. A number of factors contribute to this change. Soil erosion, loss of soil nutrients, groundwater pressure, volcanic eruptions etc are some of the natural factors that cause landslides. The Mameyes landslide, caused by the excess accumulation of rains resulted in the destruction of more than a hundred homes in the coast of Puerto Rico.