Classification, causes and impacts (social, economic, political, environmental, health and psychosocial) of disasters

Classification of disasters:
Disasters are primarily classified as:

1. Natural disasters and
2. Man-made disasters

Natural disasters are caused due to natural phenomena. Examples are:

• Floods
• Droughts
• Cyclones
• Earthquakes
• Tsunamis
• Volcanoes
• Landslides
• Avalanche
• Blizzard (Snow storm)
• Wind chill
• Sand storms

Man-made disasters are caused primarily due to human negligence. Examples are:

• Explosions
• Leakage of toxic chemicals
• Pollution
• Deforestation, Forest fires
• Dam failure
• Wars, Weapons of mass destruction (WMD), Biological weapons, Chemical weapons, etc.

Natural disasters can further be divided into 

• Hydrometeorological based disasters and
• Geological based disasters

Hydrometeorology is the study of exchange of energy and water between the lower atmosphere and Earth's surface. Examples of hydrometeorological disasters are:

• Cyclone
• Flood
• Drought
• Wind chill
• Snow storm
• Sand storms. etc

Geology is the science of study of the Earth. Examples of geological based disasters are:

• Earthquake
• Volcano
• Landslide
• Tsunami, etc

Earthquake:

The Earth is made-up of rocks, tectonic plates and molten magma at the core. The tectonic plates are in constant motion relative to each other. As the plates move against each other, any irregularity causes an abrupt jerk resulting in tremendous energy being released which is experienced on the surface as an Earthquake.

Volcano:
The Earth's core is made up of molten magma under pressure. When this molten magma finds its way to the surface of the Earth through cracks or fissures it erupts with great force spewing red hot lava. Volcanoes occur under the oceans on the sea bed also. They cause severe damage to life and property. Sometimes volcanoes remain dormant for several years before becoming active again. In the past, volcanoes have occurred in Italy(Mount Etna), Indonesia(Mount Merapi), Japan(Sakurajima), United States(Mount St. Helens), Ethiopia(Erta Ale), etc.

Landslide:
Landslide refers to a type of mass wasting. Examples include:

• Rock falls
• Deep seated slope failures
• Mud flow and
• Debris flow

Tsunami:
Tsunami is Japanese meaning tidal wave or  a  harbour wave. It occurs due to disturbances in the sea floor. It is a series of waves in a water body caused by displacement of large volume of water in an ocean.

Disasters are also classified as:

• Extraterrestrial disasters: These types of disasters are caused by collision of celestial bodies. Space telescope data reveals 4700 potentially hazardous asteroids with diameter greater than 330 feet are present near the Earth. Other types of extraterrestrial hazards are:
• Magnetic storms
• Catastrophic Earth changes
• Meteorite Impacts and
• Impacts from near-earth objects

Man-made disasters:

• These hazards man-made or human induced disasters. They are caused primarily due to human activities leading to loss of life and property along with causing damage to the regions economy and productive capacity. Examples of these disasters are:
• Environmental pollution
• Terrorism
• Destruction of property
• Road & rail accidents
• Explosions
• Chemical spills
• Industrial accidents
• Nuclear accidents, etc.
• Physical hazards that are caused due to developmental activities. Examples include:
• Deforestation
• Desertification
• Loss of natural resources
•  Pollution
• Waste disposal, etc.
• Technological hazards that are caused due to interaction of society, technology and the natural environment. Examples include:
• Explosions
• Wars
• Release of  toxic substances into the environment
• Oil spills, etc

Environmentalists have further categorized technological hazards into:

• Industrial Hazards
• Structural collapse hazards
• Nuclear hazards
• Computer hazards and
• Transportation hazards

Biological hazards or biohazards:

• These type of hazards originate from biological sources. Examples are:
• AIDS
• Malaria
• Severe epidemics in plants and animals (SARS)

Biohazards are further categorised into:

• Pathogens (Example: Anthrax, Small Pox, Influenza, Plague etc)
• Toxins 

Social hazards originate from social systems such as:

• Population explosion
• Famine
• Warfare
• Conflict
• Terror attacks
• Holding people hostage etc

Causes of disasters:

• Earthquakes are mainly caused by slippage within geological faults but also due to volcanic activity, landslides, mine blasts and nuclear tests.
• Landslide is a geological phenomenon that includes a wide range of ground movements like rock falls, deep failure of slopes and shallow debris flow that occurs offshore, coastal and onshore environments.Gravity is the primary driving force along with contributing factors like slope stability.
• Tsunami is a series of water waves caused by displacement of large body of water. The 2004 Indian ocean tsunami was the deadliest in human history causing the death of 2,30,000 people in the countries surrounding the Indian ocean.
• A volcano is a rupture in the Earth's crust that allows hot magma and volcanic ash from the Earth's interior to erupt on the Earth's surface.
• A flood is an overflow of water that submerges vast areas of land. Floods occur in rivers when flow capacity exceeds the capacity of the channel
• Landslides also called a landslip or mudslide occurs when the slope changes from a stable to an unstable condition due to groundwater pressure, weakening of a slope due to saturation from snow melt or heavy rainfall. Landslides are also caused due to deforestation, mining at the foot of the slope, excess withdrawal of ground water, construction activity and explosive activity in the vicinity
• Droughts are caused due to less or no rainfall combined with excessive withdrawal of groundwater.
• Snow storms and sand storms occur in cold and desert regions respectively. Snow storms occur in the cold mountainous regions and consist of freezing winds combined with snow reducing visibility and related hazardous conditions. Sand storm is a meteorological phenomena in arid and semi-arid regions. Sand storms may cause asthma and other related respiratory problems. Sand storms or dust storms involve transport of fine sand particles from one place to another. A sand storm can transport and carry large volumes of sand unexpectedly.

Impacts of disasters:
Disasters may have the following effects on communities as listed below.

1. Social impacts: The social impacts of a disaster refer to the tangible and intangible effects on a society and the expenses to rebuild the society to the stage that existed before the disaster occurred. The most common social impacts on a community involve:
1. increased mental health issues
2. alcohol misuse
3. domestic violence
4. chronic diseases and
5. short-term unemployment
2. Economic impacts: Any disaster destroys tangible assets such as buildings and equipment. Disasters have severe short-term economic impacts. The costs of disasters rise exponentially with economic development. Disasters affect the infrastructure of a community in a manner that all other projects requiring funds are stopped and diverted to reconstruction and rehabilitation work
3. Political Impacts: Disasters fundamentally test a government's preparedness and capacity to deal with a disaster. Government's should be aware of natural disaster risks in their region and set regulatory measures in place before the disaster occurs. If a government has done a poor job responding to a disaster they may be voted out or political unrest may occur in response to a disaster.
4. Environmental impacts: Disasters have a profound effect on the environment. They cause a temporary or permanent effect on the environment depending the type of disaster. Earthquakes modify the topography of the terrain, Volcanoes release several tons of carbon-dioxide and other toxic gases. In addition, they destroy the local landscape and anything that comes in contact. Floods cause widespread destruction of the local region and habitat. They also cause loss of life and severe erosion.
5. Health impacts: Disasters impact the health of affected people in several ways. People may suffer from physical injuries that may be temporary or permanent. Affected people may suffer psychologically and suffer from mental illnesses. The health effects may last much longer than the disaster itself. The health effects of a disaster are unavoidably linked to the social and economical effects of any disaster.
6. Psychosocial impacts: Psychosocial impacts refers to the effect caused by the environment on the social and or psychological aspect on an individual or community due to a disaster. Several psychiatric disorders may affect psychological and social aspect of the affected individual's life. Disasters may diseases such as PTSD, depression, extreme stress, anxiety and a range of mental diseases.