write a long essay on man made disaster and their examples
Answers
Answer:
Man-made disasters:
When the disasters are due to carelessness of human or mishandling of dangerous equipment’s they are called man-made disasters. Common examples of these disasters are train accidents, aero plane crashes, collapse of buildings, bridges, mines, tunnels, etc.
Natural Disasters:
Some of the common natural disasters, their impact on environment, and their prevention, control and mitigation are discussed below:
Earthquakes:
An earthquake is the shaking of the earth’s surface caused by rapid movement of the earth’s crust or outer layer. Ever since it came into existence 4.6 billion years ago, the earth has been a dynamic, evolving system. The position of the different continents and oceans that we see today, has changed a number of times in the earth’s history.
The earth is primarily composed of three layers:
1. The outer crust,
2. The middle mantle, and
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3. The inner core
The Earth’s outer layer or crust is made up of a number of zig-saw pieces like structures that interlock into one another. These pieces are called tectonic plates. These plates are in continuous motion over the mantle, which is known as tectonic movements. These tectonic processes are also responsible for the mountain building processes.
The plates that are moving past over one another are slowed by friction along their boundaries. Due to this, the rocks are under strain. When the stress on the rocks exceeds certain limits, the rocks rupture and form a fault along which the rocks are displaced during tectonic movements. This sudden rupture of the rocks releases energy in the form of earthquake waves (Fig. 18.1).
Elements of Earthquake
Richter Scale
Thus earthquake is a form of energy, which is transmitted to the surface of the earth in the form of waves called seismic waves. The study of earthquakes and the waves they create is called seismology (from the Greek seismos, “to shake”). Scientists who study earthquakes are called seismologists. The instrument that records the seismic waves is called seismograph.
The exact spot under the earth surface at which an earthquake originates is called the focus or hypocenter. The point on the earth surface above the focus is called the epicenter. The Richter scale is used to measure the intensity of earthquakes. The intensity is measured on a scale of 0 to 8 and above (Table 18.1).
Tsunami Waves
Impact of Earthquake on the Environment:
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The destruction, an earthquake causes, depends on its magnitude and duration or the amount of shaking that occurs. In the last 500 years, earthquakes around the world have killed several million people. Earthquake is one of the most catastrophic natural disasters. Massive loss of life and property occurs due to collapse of buildings. Besides, roads, bridges, canals, electric poles, etc. are severely damaged. Certain regions of the earth are more prone to earthquakes.
These are places located in the unstable regions of the earth crust, which are subjected to tectonic activities. Countries like Japan, parts of Southeast Asia, Turkey, Iran, Mexico, etc. are affected by severe earthquakes. In India, the entire Himalayan region, parts of the Gangetic Plain, Kutch and Andaman and Nicobar islands are in the earthquake hazard zone (Table 18.2).
The major impacts of earthquakes are as follows:
A Brief List of Recent Major Indian Earthquakes
Shaking of the ground and surface rupture:
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This is the main cause of destruction in which buildings, bridges, roads, canals and other structures are damaged.
Liquefaction:
Earthquakes make sands and silts to transform from a solid to liquid state. This also results in building collapse.
Landslides:
Earthquakes of high intensity often trigger many landslides in the hilly regions.
Fires:
It is a major hazard associated with earthquakes. The shakings of the ground and building damage often break the gas pipes and electric lines that cause fires.
Changes in the land elevation:
The surface topography of a region and groundwater conditions are altered after an earthquake.
Tsunami:
It is a Japanese term meaning ‘harbour waves’. Tsunamis are massive sea waves that are mainly caused due to earthquakes in the ocean floor or possibly due to an undersea landslide or volcanic eruption. When the ocean floor is tilted or offset during an earthquake a set of waves is created similar to the concentric waves generated by an object dropped into the water.
These waves are massive in size and gain height as they approach the seashore. Tsunamis up to the height of 30 m are recorded (Fig. 18.2). Tsunamis are the most catastrophic among natural disasters as they affect a very wide geographical area. The tsunami of 26 December, 2004 killed around three lakh people and affected parts of Indonesia, Andaman and Nicobar Islands in India, Sri Lanka and even Somalia.