Natural Disasters- When Mother Nature is furious

Feb 15, 2017 | Science, World

A natural disaster is a sudden, catastrophic event caused by natural processes of the Earth. Different types of natural disasters include floods, earthquakes, hurricanes, volcanic eruptions and many more. There are varying estimates that peg the number of natural disasters per year across the world in the range of 500-1000. Some of the most recent examples include the Kaikoura (New Zealand) earthquake on 14 November 2016 , the Nepal earthquake in 2015 and the Indian Ocean tsunami in 2004.

Nature is analogous to a person with split personality (like the character in Strange Case of Dr. Jekyll and Mr. Hyde); at its best it is beautiful and mesmerizing but at its worst, can be disastrous and catastrophic. There are many types of natural disasters that strike different parts of Earth and cause extensive damage to life, property and economic health in the affected areas. Some common examples of natural disasters include floods, hurricanes, earthquakes, tsunamis, tornadoes and volcanic eruptions. While many natural disasters are the result of natural geological and meteorological processes of the Earth, human activities such as forest degradation, pollution, engineering and construction are also altering natural systems dramatically and destabilizing climate, resulting in such disasters. In this article, we look at various types of natural disasters and their deadliest occurrences from the past, that continue to remind us that Nature is indeed the most powerful force after all!

Types of Natural Disasters- The Deadliest Ones


Features & Characteristics: A hurricane (also called tropical cyclone or typhoon) is a giant, spiraling tropical storm characterized by a low-pressure center and a spiral arrangement of thunderstorms that produce heavy rain and strong winds. Wind speeds in a hurricane can reach up to 300km/hr in very severe occurrences and can cause over 9 trillion liters of rainfall per day! The center of a hurricane, also called its eye, is typically about 30-65km in diameter and notoriously calm. The outer edge of the eye, called the eyewall, is where the greatest wind speeds and highest precipitation occur. Hurricanes cause far greater damage to coastal regions and typically weaken over land.

Deadly Occurrences: The deadliest hurricane on record is probably the Bhola cyclone in 1970, which struck the Ganges delta in Bangladesh and killed more than 300,000 people. Hurricane Katrina is estimated as the costliest hurricane worldwide, causing damages of over $100 billion. The Great Hurricane of 1780 in the Caribbean islands and Typhoon Nina in China in 1975 are two other instances which caused great loss to life, killing about 22000 and 100,000 people respectively.

Deadliest Natural Disasters: Hurricane


Features & Characteristics: A drought is a continuous or extended period of dry spell caused by lack of rainfall and other forms of precipitation. Depending on the severity, droughts can last up to a month or several years and have an adverse impact on the ecosystem, agriculture and economy of the affected areas. A drought can result in prolonged shortages in water supply and loss in water quality, loss of biodiversity and agricultural output, creation of deserts, famines and malnutrition, increased pollution levels and diseases as well as mass migration and displacement of human and animal life.

Deadly Occurrences: One of the worst natural droughts was in China, which began in 1875 and lasted until 1879, when the rains finally returned. It resulted in the deaths of 9-13 million people! About a 100 years earlier, there was an El Nino event in India which caused a monsoon failure for four consecutive years beginning from 1789. According to studies, about 11 million died of the accompanying starvation and disease epidemics.

Natural Disasters Examples: Drought

Volcanic Eruption

Features & Characteristics: Volcanic eruption is a natural event in which lava, ash and many gases are expelled from a volcanic vent. There are many different types of eruptions but in terms of activity, can be categorized as either explosive or effusive. Explosive eruptions are primarily gas-driven explosions that propel magma and fragmented lava. Effusive eruptions, however, involve outpouring of lava as a thick, sticky liquid without a significant eruption. The Volcanic Explosivity Index (VEI) is a scale from 0 to 8 that measures the strength of volcanos and is similar to the Richter Scale used for Earthquakes, where every interval represents a ten-fold increase in magnitude.

Deadly Occurrences: One of the most powerful volcanic eruptions was the eruption of Mount Tambora (VEI=7) in Indonesia in 1815. The eruption resulted in 70000-90000 human deaths and was so massive that it resulted in average global temperature drop of 0.530 C, causing 1816 to be known as the Year Without a Summer! Other deadly eruptions were the eruption of Krakatoa (again in Indonesia) in 1883, which resulted in about 36000 deaths and devastating tsunamis and the eruption of Mount Vesuvius (Pompeii, Italy) way back in 79 AD, which released a hundred thousand times the thermal energy of the Hiroshima bombing and wiped out several Roman settlements!

Recent Natural Disasters: Volcanic Eruption


Features & Characteristics: A flood is an overflow of water from lakes, rivers or oceans that submerges nearby land. Floods are of various types such as Over-bank or Riverine (caused by overflowing of rivers), Flash Floods (caused by rapid rise of fast moving water in a very short time frame), Coastal flooding (often caused by thunderstorms, hurricanes and tsunamis) and Catastrophic floods (caused by engineering or infrastructural failures such as collapse of a dam). Floods can take on severe levels and cause massive destruction to life, property and economy of the affected area.

Deadly Occurrences: One of the deadliest occurrence of floods was the 1931 China floods on the Huang He, Yangtze and Huai rivers due to thawing after heavy snowstorms and heavy rains. It resulted in about 3.7-4 million human deaths from drowning, starvation and water-borne diseases! It is also the deadliest natural disaster known in terms of loss of life. In total, 5 out of the top 10 deadliest floods ever recorded occurred in China- a list which also includes the calamitous Huang He flood of 1887 that resulted in about a million deaths. 4 of the deadliest floods occurred in the low-lying Netherlands, primarily due to storm surges.

Types of Natural Disaster: Flood


Features & Characteristics: An earthquake is a sudden release of energy in the Earth’s crust caused due to tectonic plate movements. The movements generate seismic waves and result in a perceptible shaking of the Earth’s surface that can be violent enough to destroy entire cities. While earthquakes are generally caused by rupture of geological faults, they can also be caused by volcanic activity, landslides, mine blasts and nuclear tests. The point on the ground directly above the origin of the tremor is called the epicenter and is the worst affected area. The magnitude of an earthquake is measured using the Richter Scale and based on current instrumentation, it is estimated that 500,000 earthquakes occur each year around the world!

Deadly Occurrences: The deadliest known earthquake was the Shaanxi earthquake that rocked China in 1556. Measuring 7.9 on the Richter scale, it killed approximately 830,000 people and destroyed 840 km stretch of land. The second deadliest earthquake was the more recent Tangshan earthquake in China in 1976. Measuring 7.8 on the Richter scale, it resulted in 650,000-779,000 deaths and caused heavy damage to property till as far as Beijing, 140km from the epicenter! The Indian Ocean earthquake of 2004 that resulted in about 280,000 human deaths and caused massive destruction was significantly more in magnitude, measuring between 9.1-9.3 on the Richter scale.

Types of natural disasters and calamities- Earthquake


Features & Characteristics: Tsunami, literally meaning “harbor wave”, is derived from the Japanese words tsu (meaning harbor) and nami (meaning wave). A tsunami is a series of giant water waves generated by water displacement generally occurring in oceans. This water displacement can be caused by a number of reasons such as earthquakes, volcanic eruptions, landslides and glacier calving. Tsunamis are also sometimes referred to as tidal waves because they initially resemble a rapidly rising wave, though they aren’t actually tidal in nature. In the open ocean, they travel up to 800 km/hr but appear only a foot or so in height, making them difficult to detect. As they approach the coastline and enter shallow waters, they slow down but gain in height, smashing into land with waves as high as 100 feet or more and causing massive destruction to life and property.

Deadly Occurrences: The 2004 Indian Ocean tsunami is one of the deadliest tsunami occurrences and among the worst natural disasters ever, which killed about 230,000-280,000 people and caused widespread destruction in 14 countries, including Indonesia, Sri Lanka, India and Thailand. The tsunami was triggered by an underwater earthquake, with a magnitude of 9.0-9.3, off the coast of Sumatra. Other deadly occurrences of tsunamis were caused by the Messina earthquake (1908, Italy) and Krakatoa volcanic eruption (1883, Indonesia), which resulted in estimated deaths of 75,000-200,000 and 36,000-120,000 people respectively.

Types of natural disasters- Tsunami


Features & Characteristics: A tornado, also known as twister or whirlwind, is a violently rotating column of air that is in contact with the Earth’s surface as well as a thunderstorm cloud. Appearing as a large spinning funnel, a tornado is often encircled by debris and dust. While most tornadoes have wind speeds less than 180 km/hr and stretch about 80 meters across, the more extreme tornadoes can attain wind speeds of more than 480 km/hr and stretch more than 3 km across. Tornadoes have been recorded on every continent except Antarctica but are more prominent in North America. The strength of a tornado was earlier measured using the Fujita scale (F-scale), but are currently measured using the Enhanced Fujita scale (EF-scale), which comprises of 6 categories from EF0 to EF5 and a tornado is classified into one of these categories based on factors such as wind speed and damage indicators.

Deadly Occurrences: The deadliest tornado occurred in the Manikganj district, Bangladesh in 1989. The tornado killed about 1300 people and injured 12,000 people, while about 80,000 people were left homeless. Bangladesh was also hit by a deadly tornado earlier in 1969, which claimed about 920 lives. The Tri-state tornado (1925) is the deadliest tornado to have struck the U.S. in terms of casualties, resulting in 695-747 people killed. The 2011 Super Outbreak that struck the U.S. saw 362 tornadoes over a period of 3 days, including 211 in a 24-hour period alone! It killed 348 people and injured about 2200 people. It is also the costliest tornado recorded, resulting in damages of about $11 billion.

Types of natural disasters and calamities- Tornado


Features & Characteristics: Wildfire is an uncontrollable fire in combustible vegetation (such as forest or grass) that occurs in a woodland or the countryside. Depending on the kind of vegetation where the wildfire occurs, it may be classified as forest fire, grass fire, bush fire, hill fire or desert fire. Wildfires may be ignited due to various reasons such as lightning strikes, volcanic eruptions or spontaneous combustion in hot and dry climate due to substances with low ignition temperature such as hay, straw and peat. Wildfires may also be caused by humans through unattended campfires, cigarette butts, sparks from equipment and slash-and-burn clearing. The severity of a wildfire depends on flammable material present, weather conditions, vegetation density and topography of the area.

Deadly Occurrences: The deadliest wildfire in history took place in Peshtigo (U.S.) in 1871 when small fires to clear forest land were amplified greatly by high winds in the dry conditions and caused the spread of the fire on either side of the Peshtigo river, burning a large part of the town and killing 1200-2400 (estimated) people. Millions of dollars worth of property was also destroyed. Other deadly occurrences were the Kursha-2 (Soviet Union) firestorm in 1936 that killed about 1200 people and Cloquet fire (U.S.) in 1918 that was caused by sparks on the railroads & dry conditions and resulted in 453 human deaths as well as injuries to about 52,000 people.

Types of natural disasters and calamities- Wildfire


Features & Characteristics: An avalanche, also called a snow slide or snow slip, is a rapid flow of snow down a sloping surface such as a mountainside. Avalanches are caused when the snowpack (or layers of accumulated snow) is disturbed or weakened by events such as new or heavy snowfall, deforestation, earthquakes or even natural movement of animals. Avalanches may be slow to pick up but once initiated, they accelerate very quickly and grow in mass and volume as they entrain more snow and flow down the steep slopes. Although composed primarily of flowing snow and air, avalanches can also entrain rocks & trees and their destructive capability is the result of their potential to carry enormous masses of snow at very high speeds. They are mainly of two types: loose snow avalanches and slab avalanches.

Deadly Occurrences: The deadliest avalanche originated in Mount Huascarán, Peru in 1970 and buried the nearby towns of Yungay and Ranrahirca under ice and rock. The avalanche, caused by the Ancash earthquake, was about 900 meters wide and 1.6 km long and advanced 18 km at a speed of 280-335 km/hr, killing about 20,000 people. The total casualties from the earthquake and the resultant avalanche is estimated to be in the range of 66,794-70,000. Mount Huascarán was also the site of a previous avalanche in 1962 that killed about 4000 people. The Tyrolean Alps avalanche (1916) in Italy was another deadly occurrence that caused about 10,000 human deaths.

Types of natural disasters and calamities- Avalanche