Natural Disasters and their influence on nature

Introduction

Since the beginning of time, natural disasters have played a critical role in the development and subsequent survival of humanity as well as reshaping nature so as to maintain balance. Natural disasters occur unexpectedly, with no detectable consistency and leave permanent traces in nature which in most cases remain evident in nature and in society decades after they occurred. Natural disasters include floods, hurricanes, landslides, avalanches, droughts, heat waves, windstorms, forest fires, tsunamis, earthquakes and volcanic activities. It is important to note that these naturally occurring phenomena are referred to as natural hazards as opposed to natural disasters (Boustan, Kahn and Rhode, 2012). Natural hazards are only redefined as natural disasters due to the effect on humanity and human activity. Natural disasters in most instances result in severe disruptions in the normal functioning of a society triggering loss of human life, material wealth and environmental loss which in most cases leave societies in such a position as to have the inability to recover solely on their own resources. This paper seeks to discuss types of natural disasters and the impact on nature as well as on human development.

Natural disasters

Natural hazards include all hostile natural phenomena and processes which tend to adversely alter the natural environment and man’s activities. Natural disasters are classified into two categories based on origin. Natural disasters originate either from hydro meteorological origins or from geological origins. Geophysical disasters involve eruptive volcanic activity, earthquakes and tsunamis (Castro et al., 2010). Hydro meteorological disasters include phenomena such as forest fires, heat waves, hurricanes, flood, avalanche, landslides, wave surges and windstorms (Boustan, Kahn and Rhode, 2012).

Earthquakes

A majority of earthquakes and volcanic activity are witnessed at close proximity to plate boundaries. When plate boundaries move towards one another convergent boundaries are formed and in the case where one plate is continental and the other oceanic, subduction zones are formed. Known subduction zones are in Asia, New Zealand, along the Pacific coast of North and South America and in Indonesia. Earthquakes are known to be felt when earth’s crust distorts under the effect of stresses caused during tectonic plate movements (Castro et al., 2010). Many of the earthquakes experienced occur along boundaries which lie between plates. For instance the Islands of Japan lie on top of such a boundary where one tectonic plate is forced under another tectonic plate thus the numerous reported cases of earthquakes in Japan.

Deep earthquakes occur in regions where tectonic plates collide and may go as deep as 700km (Hyndman and Hyndman, 2010). in regions where tectonic plates slide past each other, such as in New Zealand and California regions earthquakes experienced are shallower. Shallow earthquakes are experienced in regions where tectonic plates pull away from one another and these are mostly on sea ridges (Castro et al., 2010).

Earthquakes that do not occur on tectonic plate boundaries are referred to as intraplate earthquakes. In Tasmania and mainland Australia all earthquakes experienced are intraplate earthquakes. It is important to note that such earth quakes occur less frequently though major earthquakes do sometimes occur (Pfeifer and Pfeifer, 2013). These earthquakes appear to be triggered by thrust faults whereby rocks are squeezing and being compressed due to plate movements at the far away boundaries.

Volcanic earthquakes result from the movement of molten rock aptly referred to as magma stored in reservoirs existing under volcanoes. Pressure within such reservoir force the magma to move upwards fracturing the rock above as it forces its way up the volcano. Such earthquakes are in most instances mild though volcanic tremors do occur due to the movement of magma in the reservoir preceding major volcanic activity. These volcanic tremors are important warning signs for impeding volcanic eruptions (Reilly, 2009).

Foreshocks refer to earthquakes of small magnitudes which sometimes occur in the same region as a major earthquake that may follow. Minor rock fractures due to stresses prior to major earthquakes referred to as the main shock result in the occurrence of foreshocks (Boustan, Kahn and Rhode, 2012). Foreshocks may occur up to a year before the main shock. However it is important to note that not all main shock earthquakes have foreshocks thus they are not a sure means for early warning signs for disaster preparedness.

Aftershocks on the other hand are similar to the foreshocks in magnitude but these tend to occur after main shock earthquakes (Hyndman and Hyndman, 2010). They are as a result of readjustments occurring in the main shock region to counter the fault movements that were the cause of the main shock earthquake. Aftershocks may also arise due to on-going displacement along fault lines. It is important to note that not all earthquakes have aftershocks.

Earthquakes have a profound influence on nature as they are absolutely necessary for the release of stresses building up below the earth’s crust as the tectonic plates readjust themselves dependent on the activities occurring perpetually beneath the crust. According to geologists, the five continents were once a single land mass and tectonic plate movements caused the landmass to split along the boundaries (Boustan, Kahn and Rhode, 2012). Earthquakes have redefined the geography of different places on the earth’s crust by altering river courses, creating gorges, mountains and lakes.

Tsunamis

The word tsunami is essentially a Japanese word which translates to mean harbour wave. The tsunami as a natural hazard is in most cases as a result of the occurrence of some other natural hazard such as volcanic eruptions, earthquakes or major landslides. It was recently proven that tidal waves are quite different from tsunamis (Castro et al., 2010).

Tsunamis are not generated as a result of wind action out in the ocean but result from natural hazards occurring deep in the ocean floor. Earthquakes on the seabed, underwater volcanic activity or submarine landslides or landslides and in rare cases meteor crashing into oceans from outer space give rise to tsunamis. However, for an earthquake to result in a tsunami, it has to have a magnitude of close to 7.0 on the Richter scale. Almost 90% of all reported tsunami occurrences are in the Pacific Ocean (Castro et al., 2010).

Tsunamis occur as a series of very huge oceanic waves precipitated by a very rapid and large scale displacement of the water in the ocean. In the deep ocean, tsunami waves are barely visible but on the shores, one can notice water receding back to the ocean. However, in the deep ocean tsunami waves are known to travel at speeds greater than 800Km/h and can effortlessly cross entire ocean floors (Castro et al., 2010). As the waves get to shallower parts of the ocean they rise above the surface of the water and can rise up to 125 feet high. These wave trains tend to cause massive devastation along the shores where they can move several hundred meters inland resulting in flooding.

Tsunamis are basically generated when the ocean bed suddenly experiences some degree of deformation which may be up to 7.0 on the Richter scale causing a massive vertical displacement of the water above the natural hazard (Reilly, 2009). This is because such activity causes the ocean water to lose its equilibrium position.

Tsunamis are known to disrupt entire ecosystems beneath the ocean and more so are known to cause serious damage to properties along coastal lines as well as loss of life. Tsunamis are also known to cause a lot of pollution as they tend to move garbage washed out to sea back to the coastline thus degrade the environment significantly (Hyndman and Hyndman, 2010). They also cause floods along the coastline resulting in erosion, destruction of vegetation and in some instances affect factories set up close to the coastline carrying back hazardous wastes to the ocean. In this way, tsunamis indirectly affect ecosystem such as marine life in many ways both directly and indirectly.

Volcanoes

Presently, there are numerous volcanoes the world over. As the global population grows, the population density in potentially hazardous volcanic regions continues to increase. Volcanoes are known to be destructive while at the same time they create. The term volcano has its origins in the tiny Island of Vulcano located of Sicily in the Mediterranean Sea (Hyndman and Hyndman, 2010). Ancient residents of this island believed that a volcano was a chimney for the forge run by Vulcan, the blacksmith for the Roman gods. During volcanic eruptions they believe that Vulcan was creating thunder bolts for Jupiter, king of the roman gods or forging out weapons for Mars the God of war.

Volcanoes are basically mountains formed from a process that differs in the manner with which mountains tend to form. Volcanic mountains are formed from the accumulation of lava and ash which are spewed out during volcanic activity (Reilly, 2009). Volcanoes have a conical form built about a vent which essentially originates from the reservoirs of magma beneath the earth’s crust.

Magma is molten rock existing beneath the earth’s crust. Occasionally magma forces its way up to the earth’s crust through vents and is deposited on the earth’s crust. When magma reaches the earth’s surface it is referred to as lava. Magma ascends from many kilometres beneath the earth’s crust and is composed of dissolved gasses, crystals, fragments of surrounding rock emanating from the vent and molten rock (Castro et al., 2010). Magma is composed of oxygen, aluminium, silicon, calcium, magnesium, titanium, potassium and manganese. There are also other numerous trace elements in magma’s composition. As magma cools down, precipitation of various mineral crystals occurs until the process of solidification is complete upon which magmatic rock also referred to as igneous rocks is formed (Pfeifer and Pfeifer, 2013).

Lava is expelled while red hot out of the vent upon which it quickly cools down changing it colour from dark red to grey the finally to black as it solidifies into rock. Extremely hot molten lava which is rich in gasses and contains a lot of magnesium and iron elements usually flows in fluid form similar to the flow of hot tar. Molten lava with a lower gas content and is rich in elements like sodium, potassium and silicon exhibits a sluggish flow similar to that of honey and in some instances flows in blocky masses or pasty flow (Boustan, Kahn and Rhode, 2012). Non viscous magma contains numerous dissolved gasses which are released as magma forces it way up the vent as temperatures decrease marginally. These gasses are either released explosively or gently.  On the other hand, viscous magma does not allow for the movement of dissolved gasses bringing about intense pressure in the vent and are thus expelled through violent explosions upon reaching the surface.  Pumice is a rock formed during such explosive eruptions. It is a light rock as it contains a lot of bubbles and can therefore float on water. Pumice is also referred to as rock froth and in some cases fragment into small pieces which are hurled high up in the sky as volcanic cinders, ash or dust (Pfeifer and Pfeifer, 2013).

Type of volcanoes

There are four main types of volcanoes as classified by geologists. These are lava domes, composite volcanoes, cinder cones and shield volcanoes.

Lava domes are also referred to as volcanic domes. They result from comparatively small and bulbous lava masses which are quite viscous and thus cannot flow much and thus piles over and about the vent. Volcanic domes essentially grow as a result of expansion from within. As the outer surface cools and hardens yet volcanic activity continues to cause growth of the cone, the outer surface shatters into fragments and fall over (Reilly, 2009). Volcanic domes are common within craters or on the edges of large composite volcanoes.

Composite volcanoes are also referred to as stratovolcanoes form some of the most majestic landscapes on earth. Features that describe composite volcanoes include steep sides, very large and symmetric cones formed from alternate layers of volcanic ash, lava flow, blocks, cinders, and bombs. Composite cones can rise up to 8000 feet above the bases on which they stand. At the summit of a composite volcano, there exists a crater which houses the main vent or in other instances a cluster of vents (Hyndman and Hyndman, 2010). Lava flow occurs at breaks in the crater wall or fissures at the flanks. Lava that solidifies in fissures results in the formation of dykes which act to further strengthen the cone.

The cinder cone is considered as a simple type of volcano. They are formed from blobs and particles of solidified lava emanating from a single vent. As gas rich lava ix extruded explosively into the air, it disintegrates into minute fragments which after solidifying fall as cinders about the vent resulting in the formation of a circular cone. After gaseous explosions have receded, molten lava flows out onto the sides of the cone to complete the formation of a cinder cone volcano (Hyndman and Hyndman, 2010).

Shield volcanoes are as result of very fluid lava flows. Continuous flow of lava spewing out of the vent in every direction or in some instances from a group of vents results in the formation of a broad, domical shaped cone which slopes gently as it moves away from the summit vent. It has a shape that is similar to a warrior’s shield. They are as a result of thousands of very fluid lava flows referred to as basalt lava which have the tendency to flow large distances resulting in gently dipping sheets as they solidify (Castro et al., 2010). Shield volcanoes result in very large volcanoes with diameters reaching up to 4km and a height of over 2000feet.

Volcanoes affect nature in either a primary form or a secondary form. Primary effects happen immediately and are as a result of the volcano itself. Secondary effects on the other hand are as a result of the primary effects.  Primary effects include volcanic gasses composed of carbon dioxide, steam, sulphur and chlorine. Volcanic gasses are poisonous and corrosive and have an adverse effect on nature. Landslides also result directly from volcanic eruptions as heat from the cooling magma causes changes in surrounding rocks converting them into clay, landslides then occur quite easily (Castro et al., 2010). Flooding is also a primary effect emanating from volcanic activity as lava can change the geography of a region damming rivers resulting in continuous flooding.

Tornadoes

Tornadoes are regarded as some of the most destructive weather phenomenon on land. They are known to wipe out entire towns as well as scatter debris over very wide distances. The weather is dictated upon by temperature and pressure condition in the atmosphere. Tornadoes occur when air in high pressure zones interacts with air in low pressure areas. Low pressure areas draw in air that is in a high pressure state resulting in the formation of a vortex which results into a fully developed tornado. Tornadoes are synonymous with severe thunderstorms (Castro et al., 2010). Tornadoes moving on water bodies are referred to as waterspouts. The tornado funnel has wind within it which are very fast known to exceed 550km per hour (Reilly, 2009).

Tornadoes have a profound effect on nature mostly due to their destructive force. Tornadoes are associated with very fast winds which are primarily the cause of the damage. Air pressure fluctuations in tornadoes are also a factor in the destruction of property and the environment.  At the middle of tornadoes, air pressure is notably 200 millibars lower than air pressure at sea level (Castro et al., 2010). This is the main cause for manmade structure to collapse outwards when a tornado moves near such structures. Tornadoes are known to uproot trees, destroy wildlife, property damage and loss of life.

Avalanches

An avalanche can be defined as any volume of snow sliding downwards along a mountain side. It is similar to landslide although it involves the movement of snow as opposed to earth. Avalanches are also referred to as snow slides. They occur on mountains which experience extreme snow fall and accumulation. Avalanches only require a sufficient angle to occur and human activities have increased the risk of such natural hazards occurring on mountain slopes (Pfeifer and Pfeifer, 2013). As an avalanche moves towards the bottom of a mountain side it tends to gather speed and momentum such that what begins as a minor avalanche can result into a major disaster.

There are two main kinds of avalanches. Surface avalanches result from the movement of snow with different characteristics move over another snow layer with different properties. Full depth avalanches occur when the whole snow cover from the top to the earth beneath moves over the ground. An avalanche may have different types of snow determined by weather conditions, temperature and region (Reilly, 2009). It can be formed from loosely packed fluffy snow or it can be formed from tightly packed snow that separates itself from the neighbouring surrounding. Avalanches result snow compounded on a surface lacking the cohesiveness necessary to hold it on that surface on account of its weight, major temperature changes, high wind speeds or man-made causes.

Avalanches have both a positive and negative impact on nature. One positive effect on nature is that they aid in clearing affected regions of obstacles such as trees and boulders. During summer, regions which had experienced an avalanche over the winter will be clear of obstacles making moving up mountains easier for both animals and people (Reilly, 2009). Avalanches carry with them a lot of debris down mountain slopes into water ways at the mountain base. These create dams which enrich rivers and lakes with fish as breeding grounds are created through such means.

Landslides

Landslides are described as gravitational movement of a bulk of debris, earth and rock along a slope. Landslides are categorised depending on the material displaced and the mode of movement, whether a fall, avalanche, flow, spread, slide or topple. Mass movements such as mudslides, rock falls and debris flow are generic terms for describing the type of landslide. Lahars are debris flows and volcanic mudflows which occur on volcanic mountains (Reilly, 2009). There are shallow landslides which involve the displacement the top soil layer while deep set landslides involve the displacement of deeper soil materials such as the bedrock.

Landslides are caused by shear stress whereby shear stress on slope material actually exceeds that of the material’s shear strength. Landslides are influenced by factors relative to geo-environmental factors as well as terrain factors. Geo-environmental factors include weathering conditions, soil properties, slope morphology, ground water flow, and rainfall patterns and so on (Hyndman and Hyndman, 2010).

Landslides are considered as major hazards occurring in mountainous regions and hilly areas. Steep coastlines and river banks are also areas which are prone to landslides. Their effects on nature depend on size, elements on their path as well as the vulnerability of such elements.  They are known to block river courses, dam rivers which may later collapse resulting in flash floods which are in essence hazards themselves (Hyndman and Hyndman, 2010). Landslides along costal lines are also known trigger tsunamis. Landslides are a major form of soil erosion and thus affect nature in numerous ways.

Flooding

Floods are as a result of an overflow of a huge expanse of water which results in submerging of land or inflow of tidal waters from large water bodies onto land. Floods are considered as the most common and most expensive of all natural hazards. Floods are actually responsible for bringing about nearly 90% of all the destruction related to natural hazards (Hyndman and Hyndman, 2010). Flood damages occur as a result of the ground lacking the capacity to absorb more water. Floods occur during seasons with heavy rainfall such that the ground cannot take in more rain water and the water flows above ground towards rivers and lakes. Rivers then fill up and the water continues to flow unabated over landmasses.

The effects of flooding on nature are quite devastating, in cities floods have been known to destroy entire drainage systems resulting in raw sewage contaminating water bodies. The structural defects on buildings are also prevalent more so as a result of flooding. Floods cause massive erosion to occur destroying vegetation, animal populations, and marine life as ecosystems are affected abruptly. Chemicals also find their way into water bodies resulting in the destruction of marine life (Hyndman and Hyndman, 2010).

Conclusion

Natural disasters are inevitable and unavoidable and more so devastating. The severity of natural disasters is compounded by the continuous mismanagement of natural resources. It is a well-known fact that forests, wetlands and other natural resources greatly aid in mitigating the adverse effects of some natural disasters present on the environment. Natural disasters leave behind devastations and destruction which cannot be corrected and nature has to correct itself. However, it is important to realize the fact that natural disaster are in themselves acts of nature and are nature’s way of maintaining balance. It is therefore upon man to set up warning centres for different disaster to mitigate the impacts that these can have on populations living in prone areas.

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