Ecología y Medio Ambiente

Natural disaster # Desastres naturales





Topic: Final Paper on Natural Disaster


Date: November 2003



  • Introduction ___________________________________page 3

  • Peril and catastrophe___________________________page 4

  • Alternative of prevention________________________page 5

  • Floods__________________________________________page 6

  • Glaciar floods___________________________________page 7

  • Floods control__________________________________page 7

  • Earthquake_____________________________________page 8

  • Prediction of earthquake________________________page 9

  • Type of earthquake______________________________page 10

  • Drougth________________________________________page 11

  • Dryland farming_________________________________page 12

  • Cyclones________________________________________page 13

  • Volcanos________________________________________page 14

  • Tornado_________________________________________page 16

  • Datum__________________________________________page 18

  • Conclusión______________________________________page 19

  • Bibliography_____________________________________page 21


I was doubtful, and did not know what to write about in my final paper.

One day I spoke with my teacher; she suggested that I could write about natural disasters.

Then I realised that it was an interesting topic, because the people have to be prepared in one catastrophe, as they are in danger, because the catastrophes are “ natural disasters ”.

In a catastrophe the people act in different ways, produce different answers, this depends on the type of information and the motivation of each sector.

The quantity of victims, numbers of death and material damage give us an idea of scale of the catastrophe.

It's a very interesting topic because there were and there are population that suffer from this, and the natural disasters are a phenomenon of nature.


The natural media that sustains the human beings presents an equilibrium that is not continuous, but when it suffers alteration, that manifests suddenly and unexpectedly, natural catastrophe, to the natural phenomenon, that takes place in the environment, whose consequences alter the physical, social and economic order.

The natural catastrophes are classified according to how the terrestrial area are affected.

Sphere of the earth

Natural peril








Earth movement


Tropical cyclone




Forestall fire

The peril is the possibility that a certain territory suffers the consequences of a natural devastating and anomalous process.

Before this catastrophe, the people act in different ways, produce different answers, this depends on the type of information and the motivation of each sector, for example: the population may be don't know about it or maybe they deny it.

The scientists study this phenomena with great dedication and involve themselves in the study of the location, measuring and classification, while the institutions plan the actions to reduce the peril and it's effects.

The quantity of victims, numbers of deaths and material damage give us a idea of the scale of the catastrophe, but we must also take into account, that the effects in economics are so ample that it's difficult to quantify them.

In the last year the power of destruction of natural disaster is caused by human actions, such as conditions of growing demography, occupation of zone of peril, urbanization, degradation of environment and poverty, etc.

According to some scientists it isn't possible to avoid catastrophe, but we must be prepared, it's necessary to have scientific and technologic knowledge and most important of all is the cooperation, solidary in all sectors of the society.

'Natural disaster # Desastres naturales'


The effect of catastrophe depends on the natural media where it occurs, the intensity of the catastrophe and the answer of the society that is involved.

The following hints describe general alternatives about how a catastrophe could be prevented

  • Identification of peril zone and palming of the use of the soil according to this.

  • Implementation of warming systems, energy measure and contraction laws.

  • Use of information programmes and interchange of knowledge.

  • Matainance of appropriate sanitary conditions, as if there

is a catastrophe, it is a danger for the population health and arisk because illnesses transmitted by water could appear.


Floods occur when the water of river takes or streams overflow their banks and pour out onto the surrounding land.

Mainly in spring of the year, the amount of water in river and streams rises to a higher level than usual, and the excess spills over the banks, cause little damage.

Floods are caused by many different things:

If the land is hard and rocky, the water can't be absorbed.

If the ground is frozen, the rain is unable to sink into the hard earth.

Floods do not occur every spring in all mountain areas. Much depends on the amount of the snow of the snow and the of the melting process.

The discharge volume of an individual stream is often highly variable of this variability is the flash floods, unexpected torrent of muddy and turbulent water rushing down a canyon or gulch. It is uncommon, of relatively brief duration, and generally the result of summer thunderstorms in mountain.


This can be spectacular of even catastrophe. These happen when drainage within a glacier is blocked by internal plastic flow and

water is stored in or behind the glacier. The water eventually finds a narrow path to tricked out. This movement will cause the path to be enlarged by melting, causing faster flow, more melting, a larger conduit and so on until all the water is released quite suddenly.

Outburst floods occur in many glacier covered mountain ranges, some breakout regularly each year, some are completely irregular and impossible to predict.


Man was never able to prevent floods completely. But he can do a great deal to control floods lesend the damage they cause.

The two great causes of floods are too much rain and the slope of the land toward the river. Little can be done to eliminate these causes. All man science can't enable him to change the weather and prevent rainfall. All is engineering skill can't completely change the slope of large land areas.

The people have found ways to lessen the damage caused by floods. One method is to plants trees on the slope lands, these tree help the soil to absorb and retain more rain cuales.

River channels can be deepened and even the paths of river can be changed. Then, cubed evident storms or melting spokes pour huge quantities of waters into the river, the excess can often be carned off be new and deeper channels.


Any sudden disturbance within the Earth manifested at the surface by a shaking of the ground. This shaking, which accounts for the destructiveness of an earthquake, is caused by the passage of elastic waves through the Earth's rocks.

Over the centuries they have been responsible for millions of deaths and an incalculable amount of damage to property. While earthquakes have inspired dread and superstitious awe since ancient

times, little was understood about them until the emergence of

seismology at the beginning of the 20th century.


Generally, periodicities in time and space for major earthquakes have not been widely detected or accepted. One problem is that earthquake catalogs are not homogeneous in their selection and reporting. The catalog contains some information about 1,000 destructive earthquakes. The sizes of these earthquakes have been assessed from the reports of damage, intensity, and shaking.

Usually correlations are made between the physical phenomena assumed to provide the trigger and the repetition of earthquakes.

No trigger mechanism, has been found that satisfies the various criteria necessary to establish a clear physical connection.

Statistical methods also have been tried with populations of regional earthquakes. It has been suggested that the slope of the regression line between the number of earthquakes and the magnitude, mentioned in the previous section, for a region may change characteristically with time.

For prediction of the time of earthquake occurrence, a proposal is that precursory changes in a region will cause the velocity of seismic waves through the region to change.

For many years prediction research has been influenced by the basic argument that strain accumulates in the rock masses in the vicinity of a fault and results in crustal deformation. Deformations have been measured in the horizontal direction along active faults and in the vertical direction by precise levelling and tiltmeters.

Some investigators believe that changes in groundwater level occur prior to earthquakes; variations of this sort have been reported mainly from China. It should be noted that water levels in wells respond to a complex array of factors such as rainfall; thus, if changes in water level are to be studied in relation to earthquakes, such factors need to be removed.

For earthquake prediction, the significance of dilatancy is its effects on various measurable quantities of the Earth's crust, such as seismic velocities, electric resistively, and ground and water levels. The consequences of dilatancy for earthquake prediction are summarized in the Table earthquake: physical clues for prediction.

The rise of pore pressure also has the effect of weakening the rock and enhancing fault slip. Strain buildup in the focal region may have significant effects on other observable properties, including electrical conductivity and gas concentration. Because the electrical

conductivity of rocks depends largely on interconnected water channels within the rocks, resistivity may increase before the cracks become saturated. As pore fluid is expelled from the closing cracks, the local water table would rise and concentrations of gases such as radioactive radon would increase.

Less well-grounded precursory phenomena, particularly earthquake lights and animal behaviour, sometimes draw more public attention than those discussed above. Many reports of unusual lights in the sky and abnormal animal behaviour preceding earthquakes are known to seismologists, mostly in anecdotal form.


Earthquakes are caused by the sudden release of energy within some limited region of the rocks of the Earth, the release of elastic strain energy is the most important, since this form of energy is the only kind that is stored in sufficient quantity in the Earth to produce major earthquakes.

Tectonic earthquakes occurs when stresses in rock masses have accumulated to a point where they exceed the strength of the rocks. These rock fractures usually tend in the same direction and may extend over many kilometres along the zone of weakness.

Volcanic earthquake , it is likely that even here the energy released may be the result of a relatively sudden slip of rock masses

and the consequent release of elastic strain energy. The energy, may in part be of hydrodynamic origin due to the motion of magma in reservoirs beneath the volcano or to the release of gas under pressure. In the rupture, the rock masses spring back to a position where the elastic strain is less. This movement at any point may not take place at once but rather in irregular steps.

The irregular properties of fault rupture are now included in the modelling of earthquake sources, both physically and mathematically. Fault rupture starts at the earthquake focus and propagates unilaterally or bilaterally over the fault plane until stopped or slowed at a barrier.

Earthquakes have different properties depending, that causes them. The geological interpretation of a fault is given in terms of standard geometries. The usual fault model has a strike (direction from north of the horizontal line in the fault plane) and a dip (angle between direction of steepest slope and horizontal).

For a homogeneous Earth, one curve is in the plane containing For a homogeneous Earth, one curve is in the plane containing, that passes through the focus and is perpendicular to the forces of the plane. For the actual Earth, the nodal curves are displaced from these locations because of the curvature of the wave paths between focus and surface.


Lack or insufficiency of rain for an extended period that causes a considerable hydrologic (water) imbalance and, consequently, water shortages, crop damage, stream flow reduction, and depletion of groundwater and soil moisture. It occurs when evaporation and transpiration exceed precipitation for a considerable period. Drought is the most serious physical hazard to agriculture in nearly every part of the world.

There are four basic kinds of drought:

  • Permanent drought characterizes the driest climates; the sparse vegetation is adapted to aridity, and agriculture is impossible continuous irrigation.

  • Seasonal drought occurs in climates that have well-defined annual rainy and dry seasons.

  • Unpredictable drought involves an abnormal rainfall failure; it may occur almost anywhere but is most characteristic of humid and sub humid climates is irregular it affects small area.

  • Invisible drought can also be recognized: in summer, when high temperatures induce high rates of evaporation and transpiration.


The cultivation of crops without irrigation in regions of limited moisture, typically less than50 centimetres of precipitation annually.

Dry farming depends upon efficient storage of the limited moisture in the soil and the selection of crops and growing methods that make the best use of this moisture. Moisture control during crop growing consists largely of destruction of weeds and prevention of runoff. The ideal soil surface is free of weeds but has enough clods or dead vegetable matter to hinder runoff and prevent erosion.

There have been many severe droughts, and there is a natural tendency for lay observers to view these as manifestations of the greenhouse effect, several formulations of which predict drought in mid-latitude areas. Although this is a possibility, most authorities agree that the droughts and other fluctuations are expressions of climate's natural internal variability and not of externally forced change.


Cyclonic winds move across nearly all regions of the Earth except the equatorial belt and are generally associated with rain or snow. Also occurring in much the same areas are anticyclones, wind systems that rotate about a high-pressure centre. Anticyclones are so called because they have a flow opposite to that of cyclones spiralling motion, with the winds rotating clockwise in the Northern Hemisphere and counter clockwise in the Southern.

Cyclones occur chiefly in the midlatitude belts of both hemispheres

In the Southern Hemisphere cyclones are distributed in a relatively uniform manner through various longitudes.

In the Northern Hemisphere continental landmasses extend from the Equator to the Arctic, and large mountain belts interfere with the midlatitude air currents, giving rise to significant variations in the occurrence of cyclones ,and anticyclones, certain tracks are

favoured by the wind systems.

'Natural disaster # Desastres naturales'

Cyclones that form closer to the Equator differ somewhat in character from the extratropical variety. Such wind systems, known as tropical cyclones, are much smaller in diameter.

In the Atlantic and Caribbean regions, tropical cyclones are commonly called hurricanes, while in the western Pacific and China Sea the term typhoon is applied.

Extratropical cyclones: are the most abundant and exert influence on the broadest scale, affecting the largest percentage of the Earth's surface, this class of cyclones is the principle cause of day-to-day weather changes experienced in middle and high latitudes and thus is the focal point of much of modern weather forecasting.


Is the name given to the processes and phenomena associated with the surficial discharge of such material from volcanoes, geysers, and fumaroles. Volcanoes figure prominently in the mythology of many peoples who have learned to live with eruptions, but science was late in recognizing the important role of volcanism in the evolution of the Earth.

Geologists today agree that volcanism is a profound process resulting from the thermal evolution of planetary bodies.

Volcanoes are the surface manifestation of this thermal process, which has its roots deep inside the Earth and which hurls its ashes high into the atmosphere. The term volcano can either mean the vent from which magma erupts to the surface, or it can refer to the landform created by the solidified lava and fragmental volcanic debris that accumulate near the vent.

Volcanoes, are not the realm of any single scientific discipline. Rather, they require study by many scientists from several specialties: geophysicists and geochemists to probe the deep roots of volcanoes; geologists to decipher prehistoric volcanic activity; biologists to learn how life becomes established and evolves on barren volcanic islands; and meteorologists to determine the effects of volcanic dust and gases on the atmosphere, weather, and climate.

This affect humankind in many ways. Their destructiveness is awesome, but the risk involved can be reduced by assessing volcanic hazards and forecasting volcanic eruptions. Volcanism provides fertile soils, valuable mineral deposits, and geothermal energy. Over geologic time volcanoes recycle the Earth's hydrosphere and atmosphere, and explosive eruptions can affect climate.


When a tornado forms or passes over a water surface, it is called a waterspout.The name tornado comes from the Spanish tronada, which supposedly was derived from the Latin tornare. The most violent of atmospheric storms, a tornado is a powerful vortex,

or "twister," whose rotational speeds are estimated to be close to 480 kilometres per hour but may occasionally exceed 800 kilometres per hour.

The first visible indication of tornado development is usually a funnel cloud, which extends downward from the cumulonimbus cloud of a severe thunderstorm.

Tornadoes often occur in groups, and several twisters sometimes descend from the same cloud base. The forward speed of an individual tornado is normally 48 to 64 kilometres per hour but may range from nearly zero to 112 kilometres per hour.

Although much remains to be learned about tornado formation and movement, remarkable advances have been made in the effectiveness of tornado detection and warning systems. These systems involve analyses of surface and upper-air weather, detection and tracking of atmosphere changes by radar, and spotting severe local storms.

Intensity of the tornado


Velocity km/hours



From 65 to 115

Fracture the branch of the tree.

Prejudicial posters and antenna.


From 116 to 180

Unfast cover of roofs.

Displace vehicle.


From 181 to 250

Unfast top.

Root out tree.

Upset vehicle.


From 251 to 330

Roof out removes trees from root.

Destroy houses.

Elevate vehicle.


From 331 to 420

Generates rocky objects of big size.

Takes off tree trunks that keep standing.


From 421 or more

Damages structures of reinforced cement.


  • The biggest natural disasters happened in the earth during 1963_1992, were the floods that caused the greatest number of material damage and dearth of people; folowed by tropical ciclones, droughts and earthquakes.

  • In the year 1993 about 70 disasters we recorded in different cantries an

_ In Central América there were floods, tropical cyclones, epidemies, volcanic eruption and earth movements.

_ Andes América had epidemies, earthquakes and earth movement.

_ Africa had floods, earthquakes and epidemies.

_ SE asia had tropical cyclones,floods,volcanic eruption, earth movement, tornado and hailstorm.

_ SO Asia had floods, earthquake and earth movements.

Natural disasters happen in the last year


Huracane Andrés in florida_ EEUU


Floods in the Mississippi_EEUU


Earthquakes in Los Andes _EEUU


Earthquakes in Jaalisco_ México


Tornado in Itaqui _ Brazil


Huracane Paulina in Acapulco_ México


Eerth movement in Mendoza_ Argentina


Eathquakes in Asis_ Italia


Earthquake in totora_ Bolivia


Drought in Parnamburgo_ Brazil


Floods in La Cuenca del Plata


Huracane Mitch in centroamérica


Maremoto in Papúa _Nueva Ginea


Huracane in California_ EEUU


Floods in Santa Fe _ Argentina


Forest Faires in Córdoba_ Argentina


I thought about this topic for my final paper, because it's very interesting, I know the damage that natural cause.

Moreover, in the last year the power of destructed of natural disasters are caused by human action, this causes problems, as humans aren't worried about supporting the environment in good conditions.

There are a lot of natural disasters, but I chose:

  • Floods: are caused by many different things for example: if the land is hard and rocky, the water can't be absorbed; if the ground is frozen, the rain is unable to sink into the earth.

The two causes the floods are to much rain and the slope of the land .

  • Earthquakes: are cause by the sadder released of energy with in some limited region of the rocks of the earth. For prediction of the time of earthquakes occurrence, a proporsal is that precursory changes in a region will caused the velocity of seismic wave through the region to change.

  • Drought: there are for basic king of drought: Permanent drought, Seasonal drought, Unpredictable drought and invisible drought. There have been many severe droughts, and there is natural tendency for lay observes to view these as manifestation of the greenhouse effect

  • Cyclones: the principal cyclone tracks over the ocean, this surface being smoother than that of the lands and thus offering less resistance to the strong winds around low-pressure centres.

  • Volcanoes: this affects human kind in many ways because provides fertile sals, valuable mineral yhe posits and geothermal energy. Geologists today agree that volcanism is a profound presses resulting from the thermal evolution of planetary bodies.

  • Tornado: often occurs in groups, and several twisters sometimes descend from the same cloud base, the direction of motion is usually from the southwest to the northeast.

This catastrophe aren't the only phenomenon that act agamst the nature.

These final paper is very interesting because it taught me the causes that produce natural disasters.

Moreover. I learnt the cause that brings about the catastrophe, the type there are in some phenomenon, and as the population act agamest the natural phenomenon.

Finally, I can say that natural phenomena are a terrible catastrophe, that keeps the population in danger.


  • Enciclopedia Británca

  • Enciclopedia Encarta 2003

  • Internet

  • La sociedades y los espacios geográficos_ Argentina

  • Dictionary

  • Atlas geográfico universal y de la Argentina

Enviado por:Nat
Idioma: inglés
País: Argentina

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