An earthquake (also known as a quake, tremor or temblor) is the perceptible shaking of the surface of the Earth, which can be violent enough to destroy major buildings and kill thousands of people. The severity of the shaking can range from barely felt to violent enough to toss people around. Earthquakes have destroyed whole cities. They result from the sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time.
Earthquakes are measured using observations from seismometers. The moment magnitude is the most common scale on which earthquakes larger than approximately 5 are reported for the entire globe. The more numerous earthquakes smaller than magnitude 5 reported by national seismological observatories are measured mostly on the local magnitude scale, also referred to as the Richter magnitude scale. These two scales are numerically similar over their range of validity. Magnitude 3 or lower earthquakes are mostly almost imperceptible or weak and magnitudes 7 and over potentially cause serious damage over larger areas, depending on their depth. The largest earthquakes in historic times have been of magnitude slightly over 9, although there is no limit to the possible magnitude. The most recent large earthquake of magnitude 9.0 or larger was a 9.0 magnitude earthquake in Japan in 2011 (as of March 2014), and it was the largest Japanese earthquake since records began. Intensity of shaking is measured on the modified Mercalli scale. The shallower an earthquake, the more damage to structures it causes, all else being equal.
At the earth's surface, earthquakes manifest themselves by shaking and sometimes displacement of the ground. When the epicenter of a large earthquake is located offshore, the seabed may be displaced sufficiently to cause a tsunami. Earthquakes can also trigger landslides, and occasionally volcanic activity.
In its most general sense, the word earthquake is used to describe any seismic event - whether natural or caused by humans - that generates seismic waves. Earthquakes are caused mostly by rupture of geological faults, but also by other events such as volcanic activity, landslides, mine blasts, and nuclear tests. An earthquake's point of initial rupture is called its focus or hypocenter. The epicenter is the point at ground level directly above the hypocenter.
Drought in Pakistan has become a frequent phenomenon in the country. The drought of 1998-2002 is considered worst in 50 years. According to a report issued by the Economic Survey of Pakistan, the drought is one of the factors responsible for poor growth performance. Balochistan especially the western and central parts of the province remain in the grip of drought almost all year round. Drought in the country is common; if the monsoon season fails to deliver rains then drought emerges.
Biological disasters are causative of process or phenomenon of organic origin or conveyed by biological vectors, including exposure to pathogenic micro-organisms, toxins and bioactive substances that may cause loss of life, injury, illness or other health impacts, property damage, loss of livelihoods and services, social and economic disruption, or environmental damage. Examples of biological disasters include outbreaks of epidemic diseases, plant or animal contagion, insect or other animal plagues and infestation. Biological disasters may be in the form of:
- Epidemic affecting a disproportionately large number of individuals within a population, community, or region at the same time, examples being Cholera, Plague, Japanese Encephalitis (JE)/Acute Encephalitis Syndrome (AES)
- Pandemic is an epidemic that spreads across a large region, that is, a continent, or even worldwide of existing, emerging or reemerging diseases and pestilences, example being Influenza H1N1 (Swine Flu)
A chemical disaster is the unintentional refuse of one or more hazardous substances which could harm human health or the environment. Chemical hazards are systems where chemical accidents could occur under certain circumstances. Such events include fires, explosions, leakages or releases of toxic or hazardous materials that can cause people illness, injury, disability or death.
While chemical disasters may occur whenever toxic materials are stored, transported or used, the most severe accidents are industrial accidents, involving major chemical manufacturing and storage facilities. The most significant chemical accident in recorded history was the 1984 Bhopal disaster in India, in which more than 3,000 people were killed after a highly toxic vapour, (methyl isocyanate), was released at a Union Carbide pesticides factory.
Efforts to prevent accidents range from improved safety systems to fundamental changes in chemical use and manufacture, referred to as primary prevention or inherent safety. Many countries have organizations that can assist with substance risk assessment and emergency planning that is required by a wide variety of legislation.
The occurrence of nuclear or radiological disaster is of the great concern. It is accompanied with sudden release of huge amount of harmful radiations or radioactive materials or both together in environment in a small area. A nuclear/radiological disaster can occur under various circumstances Nuclear Disaster is described as a disaster caused due to an extraordinary emission of radioactive material or radiation either through explosion of a nuclear bomb or in the operation of nuclear reactors and other nuclear related activities. It is accompanied with sudden release of huge amount of harmful radiations or radioactive materials or both together in environment in a small area.
An environmental disaster is a disaster to the natural environment due to human activity, which distinguishes it from the concept of a natural disaster. It is also distinct from intentional acts of war such as nuclear bombings.
In this case, the impact of humans' alteration of the ecosystem has led to widespread and/or long-lasting consequences. It can include the deaths of animals (including humans) and plants, or severe disruption of human life, possibly requiring migration.
The term deforestation can be misused when applied to describe a tree harvesting method in which all trees in an area are removed (clear cutting). However in temperate climates, this method is in conformance with sustainable forestry practices, and correctly described as regeneration harvest. In temperate mesic climates, natural regeneration of forest stands often will not occur in the absence of disturbance, whether natural or anthropogenic. Furthermore, biodiversity after regeneration harvest often mimics that found after natural disturbance, including biodiversity loss after naturally occurring rainforest destruction.
Deforestation is the permanent destruction of forests in order to make the land available for other uses. An estimated 18 million acres (7.3 million hectares) of forest, which is roughly the size of the country of Panama, are lost each year, according to the United Nations' Food and Agriculture Organization (FAO).
Landslide and Avalanches
A landslide, also known as a landslip, is a geological phenomenon that includes a wide range of ground movements, such as rock falls, deep failure of slopes and shallow debris flows. Landslides can occur in offshore, coastal and onshore environments. Although the action of gravity is the primary driving force for a landslide to occur, there are other contributing factors affecting the original slope stability. Typically, pre-conditional factors build up specific sub-surface conditions that make the area/slope prone to failure, whereas the actual landslide often requires a trigger before being released.
An avalanche (also called a snowslide or snowslip) is a rapid flow of snow down a sloping surface. Avalanches are typically triggered in a starting zone from a mechanical failure in the snowpack (slab avalanche) when the forces on the snow exceed its strength but sometimes only with gradually widening (loose snow avalanche). After initiation, avalanches usually accelerate rapidly and grow in mass and volume as they entrain more snow. If the avalanche moves fast enough some of the snow may mix with the air forming a powder snow avalanche, which is a type of gravity current. In Latin "Ava" means earth and "Lanche" refers to a breaking down of. Slides of rocks or debris, behaving in a similar way to snow, are also referred to as avalanches.
A pest is an organism, usually an insect, which has characteristics that are regarded by humans as injurious or unwanted. This is often because it causes damage to agriculture through feeding on crops or parasitizing livestock, such as codling moth on apples, or boll weevil on cotton. An animal can also be a pest when it causes damage to a wild ecosystem or carries germs within human habitats. Examples of these include those organisms which vector human disease, such as rats and fleas which carry the plague disease, mosquitoes which vector malaria, and ticks which carry Lyme Disease.
The term pest may be used to refer specifically to harmful animals but is also often taken to mean all harmful organisms including weeds, plant pathogenic fungi and viruses. Pesticides are chemicals and other agents (e.g. beneficial micro-organisms) that are used to control or protect other organisms from pests. The related term vermin has much overlap with pest, but generally only includes those creatures that are seen to be vectors of diseases.
It is possible for an animal to be a pest in one setting but beneficial or domesticated in another (for example, European rabbits introduced to Australia caused ecological damage beyond the scale they inflicted in their natural habitat). Many weeds (plant pests) are also seen as useful under certain conditions, for instance Patterson's curse is often valued as food for honeybees and as a wildflower, even though it can poison livestock.
Forest fires can be ignited by a variety of occurrences. In addition to lightning, human-related activities start a large number of fires every year. Unattended or out-of-control campfires, a discarded burning cigarette, arson, or even equipment use can set off a blaze.
Once a forest fire has started, many factors contribute to its spread and intensity.
- Fuel - such as leaves, needles, grass, branches, and logs
- Weather, including temperature, humidity, precipitation, and wind
- Topography or landscape of the area, as steep slopes offer greater potential for increased fire intensity and more obstacles for fire fighting
More than 83% of forest fires in 2006 were started by human activities, accounting for the burning of nearly 4.4 million acres. However, lightning-caused fires burned more total area - nearly 5.5 million acres.
Urbanization refers to general increase in population and the amount of industrialization of a settlement. It includes increase in the number and extent of cities. It symbolizes the movement of people from rural to urban areas. Urbanization happens because of the increase in the extent and density of urban areas. The density of population in urban areas increases because of the migration of people from less industrialized regions to more industrialized areas. The concept “Urban Sprawl” means increase in spatial scale or increase in the peripheral area of cities. “Urban Sprawl” has its own drawbacks.
- The city and its infrastructure may not be adequately planned
- Traffic is high with increased time needed for commuting
- Essential services are not reachable within time
- City administration becomes extremely difficult
The beginning of urbanization can be traced back to Renaissance times in 16th century. Turkish assaults resulted in movement of Christians from the east to western European countries. As a result, trade grew and European cities along the coasts developed greatly. A further boost for urbanization was created with the arrival of the “Industrial Revolution”. Populations of cities in Europe and USA started to increase significantly in the 18th and 19th centuries. However, urbanization started in Asia only in the first half of the 20th century and in the second half of the 20th century in Africa, when the countries obtained independence from colonial rule. An example for a dramatic increase in extent and population of cities is Chicago in USA. The population increased from 15 people to about 20 million, within a span of 78 years.
Urbanization usually occurs when people move from villages to cities to settle, in hope of a higher standard of living. This usually takes place in developing countries. In rural areas, people become victims of unpredictable weather conditions such as drought and floods, which can adversely affect their livelihood. Consequently many farmers move to cities in search of a better life. Cities in contrast, offer opportunities of high living and are known to be places where wealth and money are centralized. Most industries and educational institutions are located in cities whereas there are limited opportunities within rural areas. This further contributes to migration to cities.