Natural disasters


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How and the different types of disasters that are found in the universe we live in.

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Natural disasters

  1. 1. Natural Disasters By Andrei Farrugia 3.1
  2. 2. Summary• A natural disaster is the effect of a natural hazard like a flood, hurricane, volcanic eruption, earthquake and heat wave.• This leads to financial, environmental or human losses. The resulting loss depends on the tecknology of the population and if they know how to prevent the hazard, also called their resilience.• If these disasters were to continue they would be a great danger to the earth.• A natural hazard will not result into a natural disaster in areas without vulnerability like strong earthquakes in inhabited areas.• Natural disasters occur in very different ways and forms and there are many reasons why they occur.• Most of them are natural and some of them are cause due to the damage that the human race is doing to the earth.
  3. 3. Avalanche• An avalanche also known as a snowslide or snowslip is a sudden, drastic flow of snow down a slope. This occurs when either natural triggers such as weight from snow or rain and earthquakes or artificial triggers such as snowmobilers, explosives or backcountry skiers that overload the snowpack.• The influence of gravity on the accumulated weight of newly fallen uncompacted snow or on thawing older snow leads to avalanches which may be triggered by earthquakes, gunshots and the movements of animals.• Avalanches are most common during winter or spring but glacier movements may cause ice avalanches during summer.• In contrast to other natural events which can cause disasters, avalanches are not rare or random events and are endemic to any mountain range that accumulates a standing snowpack.
  4. 4. Earthquakes• An earthquake (also known as a quake, tremor or temblor) is the result of a sudden release of energy in the Earth’s crust that creates seismic waves.• The 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 scale.• At the Earths 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.
  5. 5. Volcanic Eruptions• During a volcanic eruption, lava and various gases are expelled from a volcanic vent or fissure. Several types of volcanic eruptions have been distinguished by volcanologists.• There are three different metatypes of eruptions. The most well-observed are magmatic eruptions, which involve the decompression of gas within magma that propels it forward.• Volcanic eruptions arise through three main mechanisms: Gas release under decompression causing magmatic eruptions, Thermal contraction from chilling on contact with water causing phreatomagmatic eruptions and Ejection of entrained particles during steam eruptions causing phreatic eruptions.• There are two types of eruptions in terms of activity, explosive eruptions and effusive eruptions. Explosive eruptions are characterized by gas-driven explosions that propels magma and tephra. Effusive eruptions, meanwhile, are characterized by the outpouring of lava without significant explosive eruption.
  6. 6. Floods• A flood is an overflow of an expanse of water that fills land with water. Flooding may result from the volume of water within a body of water, such as a river or lake, which overflows or breaks levees, with the result that some of the water escapes its usual boundaries.• While the size of a lake or other body of water will vary with seasonal changes in precipitation and snow melt, it is not a significant flood unless such escapes of water endanger land areas used by man like a village, city or other inhabited area.• Floods can also occur in rivers, when the water flow exceeds the capacity of the river channel, particularly at bends. Floods often cause damage to homes and businesses if they are placed in natural flood plains of rivers.• While flood damage can be virtually eliminated by moving away from rivers and other bodies of water, since time out of mind, people have lived and worked by the water to seek sustenance and capitalize on the gains of cheap and easy travel and commerce by being near water.
  7. 7. Drought• A drought is an extended period of months or years when a region notes a deficiency in its water supply whether surface or underground water. Generally, this occurs when a region receives consistently low average of water by precipitation.• This global phenomenon has a widespread impact on agriculture. The United Nations estimates that an area of fertile soil the size of Ukraine is lost every year because of drought, deforestation, and climate instability.• Periods of drought can have significant environmental, agricultural, health, economic and social consequences. The effect varies according to vulnerability. For example, farmers are more likely to migrate during drought because they do not have alternative food sources. Areas with populations that depend on as a major food source are more vulnerable to drought-triggered famine.• Drought is a normal, recurring feature of the climate in most parts of the world. It is among the earliest documented climatic events, present in the Epic of Gilgamesh and tied to the biblical story of Josephs arrival in and the later Exodus from Ancient Egypt.
  8. 8. Tornadoes• A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud . They are often referred to as a twister or a cyclone. Tornadoes come in many shapes and sizes, but are typically in the form of a visible condensation funnel, whose narrow end touches the earth and is often encircled by a cloud of debris and dust.• Most tornadoes have wind speeds less than 110 miles per hour (177 km/h), are approximately 250 feet (76 m) across, and travel a few miles (several kilometers) before dissipating. The most extreme tornadoes can attain wind speeds of more than 300 mph (480 km/h), stretch more than two miles (3.2 km) across, and stay on the ground for dozens of miles (more than 100 km).• Tornadoes have been observed on every continent except Antarctica. However, the vast majority of tornadoes in the world occur in the Tornado Alley region of the United States, although they can occur nearly anywhere in North America.
  9. 9. Heat Waves• A heat wave is a prolonged period of excessively hot weather, which may be accompanied by high humidity. There is no universal definition of a heat wave; the term is relative to the usual weather in the area. Temperatures that people from a hotter climate consider normal can be termed a heat wave in a cooler area if they are outside the normal climate pattern for that area. The term is applied both to routine weather variations and to extraordinary spells of heat which may occur only once a century. Severe heat waves have caused catastrophic crop failures, thousands of deaths from hypothermia, and widespread power outages due to increased use of air conditioning.• They occur in the summer in warm climates, in an area of high pressure with little or no rain or clouds and when the air and ground easily heats much more than it’s supposed to. A static high pressure area can impose a very persistent heat wave.• Hypothermia, also known as heat stroke, becomes active during periods of sustained high temperature and humidity. Sweating is absent from 84%–100% of those affected. Older adults, very young children and those who are sick or overweight are at a higher risk for heat-related illness.
  10. 10. Blizzards• A blizzard is a severe snowstorm made by strong winds. By definition, the difference between blizzard and a snowstorm is the strength of the wind. To be a blizzard, a snow storm must have sustained winds or frequent gusts that are greater than or equal to 56 km/h (35 mph) with blowing or drifting snow which reduces visibility to 400 meters or ¼ mile or less and must last for a prolonged period of time — typically three hours or more.• Blizzards can bring near-whiteout conditions, and can paralyze regions for days at a time, particularly where snowfall is unusual or rare. The 1972 Iran blizzard, which caused approximately 4,000 deaths, was the deadliest in recorded history.• Ground blizzards require high winds to stir up already fallen snow.
  11. 11. Impact Event• An impact event is the collision of a large meteorite, asteroid, comet, or other celestial object with the Earth or another planet. Throughout recorded history, hundreds of minor impact events have been reported, with some occurrences causing deaths, injuries, property damage or other significant localised consequences. Impact events have been a plot and background element in science fiction since knowledge of real impacts became established in the scientific mainstream.• Earth has gone through periods of abrupt and catastrophic change, some due to the impact of large asteroids and comets on the planet. A few of these impacts may have caused massive climate change and the extinction of large numbers of plant and animal species.• The Moon is widely attributed to a huge impact early in Earths history. Impact events earlier in the history of Earth have been credited with creative as well as destructive events; it has been proposed that impacting comets delivered the Earths water, and some have suggested that the origins of life may have been influenced by impacting objects by bringing organic chemicals or life forms to the Earths surface, a theory known as exogenesis.
  12. 12. Tropical Cyclone• A tropical cyclone is a storm system characterized by a low-pressure centre and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapour contained in the moist air. They are fueled by a different heat mechanism than other cyclonic windstorms such as noreasters ,European windstorms, and polar lows. The characteristic that separates tropical cyclones from other cyclonic systems is that at any height in the atmosphere, the centre of a tropical cyclone will be warmer than its surroundings; a phenomenon called "warm core" storm systems.• While tropical cyclones can produce extremely powerful winds and torrential rain, they are also able to produce high waves and damaging storm surge as well as spawning tornadoes. They develop over large bodies of warm water, and lose their strength if they move over land due to increased surface friction and loss of the warm ocean as an energy source.
  13. 13. Wildfire• A wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, peat fire, vegetation fire, and veldfire may be used to describe the same phenomenon depending on the type of vegetation being burned. A wildfire differs from other fires by its extensive size, the speed at which it can spread out from its original source, its potential to change direction unexpectedly, and its ability to jump gaps such as roads, rivers and fire breaks. Wildfires are characterized in terms of the cause of ignition, their physical properties such as speed of propagation, the combustible material present, and the effect of weather on the fire.
  14. 14. Famine• A famine is a widespread scarcity of food, caused by several factors including crop failure, overpopulation, or government policies. This phenomenon is usually accompanied or followed by regional malnutrition, starvation, epidemic, and increased mortality. Every continent in the world has experienced a period of famine throughout history. Many countries continue to have extreme cases of famine. Emergency measures in relieving famine primarily include providing deficient micronutrients, such as vitamins and mineral, through fortified sachet powders or directly through supplements. The famine relief model increasingly used by aid groups calls for giving cash or cash vouchers to the hungry to pay local farmers instead of buying food from donor countries, often required by law, as it wastes money on transport costs, but more importantly, it perpetuates the cycle of dependency on foreign imports rather than helping to create real local stability through agricultural abundance. Such independence however does rest upon local conditions of soil, water, temperature and so on.
  15. 15. Solar Flare• A solar flare is a sudden brightening observed over the Sun surface or the solar limb, which is interpreted as a large energy release of up to 6 × 1025 joules of energy or 160,000,000,000 Megatons of TNT equivalent, over 25,000 times more energy released from the impact of Comet Shoemaker Levy-9 with Jupiter. The flare ejects clouds of electrons, ions, and atoms through the corona into space. These clouds typically reach Earth a day or two after the event. The term is also used to refer to similar phenomena in other stars, where the term stellar flare applies.• Flares occur when accelerated charged particles, mainly electrons, interact with the plasma. Scientific research has shown that the phenomenon of magnetic reconnection is responsible for the acceleration of the charged particles. On the Sun, magnetic reconnection may happen on solar arcades – a series of closely occurring loops of magnetic lines of force. These lines of force quickly reconnect into a low arcade of loops leaving a helix of magnetic field unconnected to the rest of the arcade.