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A natural hazard can be defined as elements that are found in the physical environment which are harmful to human beings, and originates from forces that are beyond human control. A natural hazard can either be hydrologic, atmospheric, geologic especially volcanic and seismic, and such phenomena as wildfire. Due to their location, frequency and their severity, they easily affect human life, activities and even their structures.
There are two processes, which describe the process of formation of natural hazards. These two substitute phenomena are catastrophism and uniformitarianism. Uniformitarianism is defined as the philosophy, which relies of naturalism, and it assumes that the natural processes and laws, which have shaped the universe over several years ago, have had a significant development of the world in which we live in. t his philosophy follows the principle that for the past to exist there must be the present. It also relies on the fact that all things are the same as what they were since the beginning. This philosophy therefore addresses the fact that the creation of the universe has been a uniform process. Catastrophism on the other hand refers to the process in which the earth has affected the processes that has taken place in the past and influenced by the violent wide events in the galaxy.
Uniformitarianism is the dominant paradigm, which is thought to be the accurate measure of the scientific community because it takes into consideration issues such as erosion and other incremental changes, which have shaped the appearance of the earth. This standing holds that what is happening today in the universe is so much dependent on what took place in the past and as is seen by what is going on today, this phenomenon is taking place. An example is the development of a more integrated and inclusive geological events which have developed in the universe today. Today, the formation of all the geological rock strata also explains the theory of uniformitarianism.
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Although some parts of the world are a bit vulnerable to these natural hazards, they generally occur in almost all the parts in the world. Lithospheric processes leads to hazards like earthquakes, volcanoes, and landslides.
Earthquakes occur when a mass of strain energy is suddenly released along the earth crust's fault. The reason for the occurrence of an earthquake is the resultant reactions and relationship of the foci (focus), the epicenter, and the fault. Focus is the point in the mantle of the earth where the earthquake emerges. It is that part of the earths' core where pressure builds and reactions happen causing the earth to be unstable therefore causing tremors. The epicenter is the point on the surface of the earth directly above the focus where earthquake is said to start. This is the point of reference as far as the earthquake is concerned and it is the point where a major effects and great destructions are reported due to the greatness intensity of the tremors. A fault is a line of weakness between two tectonic plates. It develops because of contraction of the tectonic plates leaving an area of weakness, which is prone to release of pressure, which builds in the mantle of the earth. The relationship of the three mentioned above is that they are all involved in an earthquake occurrence. When pressure builds in the core of the earth, which is at the focus, it tries to search for a way to get out. The place where the pressure can possibly get out is at the line of weakness called the fault and mostly it is found under the sea. The pressure follows the weakness and at the point where it meets the surface of the earth, it makes the epicenter.
Effects of earthquakes
Earthquakes are a severe threat to human due to its irregular occurrence and inadequate forecasting. When it occurs, structures near its centre are destroyed and in areas where there are high populations, many lives are lost. Earthquakes also result into faulting, landslides due to shaking of the ground especially in areas with steep topography and those with poor stability of the slope. On the other hand, settling of unconsolidated sediments result into depressions or subsidence of the earth surface. Earthquakes in the oceans cause tsunamis hence, flooding which may lead to destructions over many kilometers away from its centre.
Volcanic hazard occurs as a result of two types of eruptions, explosive eruptions comes from a rapid dissolution of a gas which comes from molten rock and its subsequent expansion as it gets near to the surface of the earth. This explosion scatters lava, fragments, and rock blocks at different distances from the point of origin hence, posing many dangers to human life.
Some effects of volcanoes
Volcanic hazards can further be divided into direct and indirect hazards. Direct hazards refer to hazards, which are directly caused by volcanic eruptions. Some of the direct hazards include; Pyroclastic flows which refer to the rapid flows of fragments of rocks, gas and hot ash, which flow down a volcano when eruptions occur. They have very high temperatures of up to 14000 F and moving at a speed of 90-140miles in an hour. They are very destructive and completely destroy everything along their way. Lava flows is another example of a direct hazard and it refers to magma that flows to the earth surface. Lava causes burning, burying, crushing and covering things along their way. In some cases, it melts snow and ice, which causes dangerous floods and lahars. This lava will dam rivers and form lakes, which overflow and cause floods.
Lava is not too destructive as compared to lahars. Lahars are mixtures of rock, mud, water, and sand, which run into valleys away from the volcano. They move very long distances downstream at a speed of 25-35 miles in an hour. They are very strong near the volcano and hence very destructive. Lahars have been historically found as the most deadly hazard of volcanic eruption. Tephra refers to an eruption and an ejection from the immediate atmosphere. Because the tephra are too large, they are thrown just near the volcano. Some small ejecta are lifted by the heat and they fall far from the source. The smallest ones will remain suspended in the atmosphere for about three years after the eruption occurred, these particles are believed to cause global warming. Volcanic gases refer to gases, which volcanoes often emit. They include carbon dioxide, hydrogen sulfide, water vapor, and hydrogen. Sulfur dioxide is very hazardous since will react with water droplets to form acid rain which destroys vegetation and causes corrosion. Since carbon dioxide is much denser that air. It will occupy the lower part of the atmosphere where organisms live. This may cause suffocation.
Indirect hazards occurring as a result of volcanic eruption include landslides and tsunami. A landslide is a massive movement of snow, rock or ice. They differ in size and ranges from small moving debris on a volcano's surface to large downfalls of the whole volcano. Although not all landslides occur due to eruptions, volcanoes are more susceptible since they have weak rocks which are fragmented. Tsunamis on the other hand refers to a long-period wave usually occurring as a result of sudden water displacement. They travel as waves through deep water at very high speeds. As they near shallow shores, they move to great heights. Though most tsunamis are known to be caused by displacement of water, volcanic eruption has initiated many of them.
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Effusive eruption is another type of eruption leading to volcanic hazard where the major hazard is the flow of the material rather than its explosion. These flowing materials vary in quantity, nature, and origin. The flow is actually governed by the topography of the surrounding, viscosity of the material and the force of gravity.
Volcanic eruptions can trigger other hazardous events and are accompanied by such hazards as; projectiles, toxic gases, lava flows, and mudflows.
Another hazard caused by lithospheric processes is the degradation. Degradation processes are those associated with change in the land cover characteristics or components. These hazards are significant in arid and semi arid areas, the natural hazards associated with such processes include; desertification, erosion and sedimentation, and salinization.
Desertification in the arid is caused by droughts; which are prolonged periods of dry spells in the cycles of the natural climates. Erosion and sedimentation result to losses which can be both economical and social. Although erosion occurs in all climatic conditions, the presence of salinity in the arid lands makes it considered as the major cause of desertification in these zones. Erosion affects plant growth hence lack of food for humans, the sediments eroded, also damages the down stream and water storage capacity is depleted resulting into reduction of regulation of natural stream flow.
Although natural hazards are caused by forces beyond human control, humans have tried to modify some of the hazardous regions and put in place measures to reduce effects of such hazards. WMO in conjunction with other national, regional, and international organizations for example, has developed activities which aim at reducing disaster risks. WMO helps the National Meteorological and Hydrological Services (NMHSs) in coordinating its efforts to help reduce human and loss of property by providing standard forecast services and giving warning in advance, assessing risks, and raising the awareness of the public. WMO has aimed at reducing the risks caused by the natural hazards by 50 % before 1920.
In the Caribbean for example, most of its countries have had warning systems installed and have had a significant reduction in loss of lives by hurricanes. This has allowed enough time for evacuation or reinforcing safety structures before the hazard is experienced. Permanent settling has also been prohibited in floodplains and has reduced the number of damages due to floods.
The need to manage flood has also brought about an approach called Integrated Flood Management, which gives a consideration to both positive and negative effects of floodwaters and the flood plains occupied by such waters. In the areas that face a lot of dry spells, irrigation has been adopted and human beings have been able to adapt to these areas
In an attempt to reduce losses by landslides, ordinances of soil analysis and proper grading have seen through a successful reduction of damages by more that 96 percent. Earthquakes effects have also been reduced by ensuring that the structures being constructed meet the standards of the seismic resistance. By doing this, such structures experience little or no effect in times of earthquakes. This has been found successful in California.
In conclusion, natural hazards have severe effects on human lives and many people in different parts of the world where such are experienced, have tried to modify their environment in order to reduce the number of damages. Since all the natural hazards are caused by forces beyond human nature, most of them cannot be done away with but little can be done to safe human lives.