Natural DisastersNatural Disasters

By Andrei Farrugia 3.1By Andrei Farrugia 3.1

SummarySummary

• A natural disaster is the effect of a natural hazard like a flood, hurricane, A natural disaster is the effect of a natural hazard like a flood, hurricane, volcanic eruption, earthquake and heat wave.volcanic eruption, earthquake and heat wave.

• This leads to financial, environmental or human losses. The resulting loss This leads to financial, environmental or human losses. The resulting loss depends on the tecknology of the population and if they know how to depends on the tecknology of the population and if they know how to prevent the hazard, also called their resilience.prevent the hazard, also called their resilience.

• If these disasters were to continue they would be a great danger to the If these disasters were to continue they would be a great danger to the earth.earth.

• A natural hazard will not result into a natural disaster in areas without A natural hazard will not result into a natural disaster in areas without vulnerability like strong earthquakes in inhabited areas.vulnerability like strong earthquakes in inhabited areas.

• Natural disasters occur in very different ways and forms and there are Natural disasters occur in very different ways and forms and there are many reasons why they occur.many reasons why they occur.

• Most of them are natural and some of them are cause due to the damage Most of them are natural and some of them are cause due to the damage that the human race is doing to the earth.that the human race is doing to the earth.

AvalancheAvalanche

• An avalanche also known as a snowslide or snowslip is a sudden, An avalanche also known as a snowslide or snowslip is a sudden, drastic flow of snow down a slope. This occurs when either natural drastic flow of snow down a slope. This occurs when either natural triggers such as weight from snow or rain and earthquakes or triggers such as weight from snow or rain and earthquakes or artificial triggers such as snowmobilers, explosives or backcountry artificial triggers such as snowmobilers, explosives or backcountry skiers that overload the snowpack.skiers that overload the snowpack.

• The influence of gravity on the accumulated weight of newly fallen The influence of gravity on the accumulated weight of newly fallen uncompacted snow or on thawing older snow leads to avalanches which uncompacted snow or on thawing older snow leads to avalanches which may be triggered by earthquakes, gunshots and the movements of may be triggered by earthquakes, gunshots and the movements of animals.animals.

•   Avalanches are most common during winter or spring but glacier Avalanches are most common during winter or spring but glacier movements may cause ice avalanches during summer. movements may cause ice avalanches during summer.

• In contrast to other natural events which can cause disasters, avalanches In contrast to other natural events which can cause disasters, avalanches are not rare or random events and are endemic to any mountain range are not rare or random events and are endemic to any mountain range that accumulates a standing snowpack. that accumulates a standing snowpack.

Earthquakes 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  Earthquakes are measured using observations from seismometers. The  moment magnitude is the most common scale on which earthquakes larger moment magnitude is the most common scale on which earthquakes larger than approximately 5 are reported for the entire globe. than approximately 5 are reported for the entire globe.

• The more numerous earthquakes smaller than magnitude 5 reported by The more numerous earthquakes smaller than magnitude 5 reported by national seismological observatories are measured mostly on the local national seismological observatories are measured mostly on the local magnitude scale, also referred to as the Richter scale. magnitude scale, also referred to as the Richter scale.

• At the Earth's surface, earthquakes manifest themselves by shaking and At the Earth's surface, earthquakes manifest themselves by shaking and sometimes displacement of the ground. When the epicenter of a large sometimes displacement of the ground. When the epicenter of a large earthquake is located offshore, the seabed may be displaced sufficiently to earthquake is located offshore, the seabed may be displaced sufficiently to cause a tsunami. Earthquakes can also trigger landslides, and occasionally cause a tsunami. Earthquakes can also trigger landslides, and occasionally volcanic activity. volcanic activity.

Volcanic Eruptions Volcanic Eruptions

• During a During a volcanic eruptionvolcanic eruption, lava and various gases are expelled from , lava and various gases are expelled from a volcanic vent or fissure.  Several types of volcanic eruptions have been a volcanic vent or fissure.  Several types of volcanic eruptions have been distinguished by volcanologists.  distinguished by volcanologists. 

• There are three different metatypes of eruptions. The most well-observed There are three different metatypes of eruptions. The most well-observed are magmatic eruptions, which involve the decompression of gas within are magmatic eruptions, which involve the decompression of gas within magma that propels it forward. magma that propels it forward.

• Volcanic eruptions arise through three main mechanisms: Gas release Volcanic eruptions arise through three main mechanisms: Gas release under decompression causing magmatic eruptions, Thermal contraction under decompression causing magmatic eruptions, Thermal contraction from chilling on contact with water causing phreatomagmatic eruptions from chilling on contact with water causing phreatomagmatic eruptions and Ejection of entrained particles during steam eruptions and Ejection of entrained particles during steam eruptions causing phreatic eruptions.causing phreatic eruptions.

• There are two types of eruptions in terms of activity, explosive There are two types of eruptions in terms of activity, explosive eruptions and effusive eruptions. Explosive eruptions are characterized by eruptions and effusive eruptions. Explosive eruptions are characterized by gas-driven explosions that propels magma and tephra.  Effusive eruptions, gas-driven explosions that propels magma and tephra.  Effusive eruptions, meanwhile, are characterized by the outpouring of lava without significant meanwhile, are characterized by the outpouring of lava without significant explosive eruption. explosive eruption.

FloodsFloods

• A A floodflood is an overflow of an expanse of water that fills land with water.  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 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 as a river or lake, which overflows or breaks levees, with the result that some of the water escapes its usual boundaries.some of the water escapes its usual boundaries.

• While the size of a lake or other body of water will vary with seasonal 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 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 such escapes of water endanger land areas used by man like a village, city or other inhabited area. or other inhabited area.

• Floods can also occur in rivers, when the water flow exceeds the capacity 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 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.  homes and businesses if they are placed in natural flood plains of rivers. 

• While flood damage can be virtually eliminated by moving away While flood damage can be virtually eliminated by moving away from rivers and other bodies of water, since time out of mind, from rivers and other bodies of water, since time out of mind, people have lived and worked by the water to seek sustenance people have lived and worked by the water to seek sustenance and capitalize on the gains of cheap and easy travel and and capitalize on the gains of cheap and easy travel and commerce by being near water. commerce by being near water.

DroughtDrought

• A drought is an extended period of months or years when a region notes a 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. deficiency in its water supply whether surface or underground water. Generally, this occurs when a region receives consistently low average of Generally, this occurs when a region receives consistently low average of water by precipitation. water by precipitation.

• This global phenomenon has a widespread impact on agriculture. The United 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 Nations estimates that an area of fertile soil the size of Ukraine is lost every year because of drought, deforestation, and climate instability. year because of drought, deforestation, and climate instability.

• Periods of drought can have significant environmental, agricultural, health, Periods of drought can have significant environmental, agricultural, health, economic and social consequences. The effect varies according to economic and social consequences. The effect varies according to vulnerability. For example, farmers are more likely to migrate during drought vulnerability. For example, farmers are more likely to migrate during drought because they do not have alternative food sources. Areas with populations because they do not have alternative food sources. Areas with populations that depend on as a major food source are more vulnerable to drought-that depend on as a major food source are more vulnerable to drought-triggered famine. triggered famine.

• Drought is a normal, recurring feature of the climate in most parts of the 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 world. It is among the earliest documented climatic events, present in the Epic of Gilgamesh and tied to the biblical story of Joseph's arrival in and the Epic of Gilgamesh and tied to the biblical story of Joseph's arrival in and the later Exodus from Ancient Egypt. the later Exodus from Ancient Egypt.

Tornadoes Tornadoes

• A A tornadotornado is a violent, dangerous, rotating column of air that is in contact  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 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 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 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 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. 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), 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 are approximately 250 feet (76 m) across, and travel a few miles (several kilometers) before dissipating. The most extreme tornadoes can attain kilometers) before dissipating. The most extreme tornadoes can attain wind speeds of more than 300 mph (480 km/h), stretch more than 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 two miles (3.2 km) across, and stay on the ground for dozens of miles (more than 100 km). (more than 100 km).

• Tornadoes have been observed on every continent except Tornadoes have been observed on every continent except Antarctica. However, the vast majority of tornadoes in the world Antarctica. However, the vast majority of tornadoes in the world occur in the Tornado Alley region of the United States, although occur in the Tornado Alley region of the United States, although they can occur nearly anywhere in North America. they can occur nearly anywhere in North America.

Heat WavesHeat Waves

• A A heat waveheat wave is a prolonged period of excessively hot weather, which may  is a prolonged period of excessively hot weather, which may be accompanied by high humidity. There is no universal definition of a heat 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 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 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 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 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 extraordinary spells of heat which may occur only once a century. Severe heat waves have caused catastrophic crop failures, thousands of deaths heat waves have caused catastrophic crop failures, thousands of deaths from hypothermia, and widespread power outages due to increased use of from hypothermia, and widespread power outages due to increased use of air conditioning. air conditioning.

• They occur in the summer in warm climates, in an area of high pressure 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 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 much more than it’s supposed to. A static high pressure area can impose a very persistent heat wave.very persistent heat wave.

• Hypothermia, also known as heat stroke, becomes active during periods of Hypothermia, also known as heat stroke, becomes active during periods of sustained high temperature and humidity. Sweating is absent from 84%–sustained high temperature and humidity. Sweating is absent from 84%–100% of those affected. Older adults, very young children and those who 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.  are sick or overweight are at a higher risk for heat-related illness. 

BlizzardsBlizzards

• A blizzard is a severe snowstorm made by strong winds. By A blizzard is a severe snowstorm made by strong winds. By definition, the difference between blizzard and a snowstorm is the definition, the difference between blizzard and a snowstorm is the strength of the wind. To be a blizzard, a snow storm must have 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 sustained winds or frequent gusts that are greater than or equal to 56 km/h (35 mph) with blowing or drifting snow which reduces 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 visibility to 400 meters or ¼ mile or less and must last for a prolonged period of time — typically three hours or more. prolonged period of time — typically three hours or more.

• Blizzards can bring near-whiteout conditions, and can paralyze regions for Blizzards can bring near-whiteout conditions, and can paralyze regions for days at a time, particularly where snowfall is unusual or rare. The 1972 days at a time, particularly where snowfall is unusual or rare. The 1972 Iran blizzard, which caused approximately 4,000 deaths, was the deadliest Iran blizzard, which caused approximately 4,000 deaths, was the deadliest in recorded history.in recorded history.

• Ground blizzards require high winds to stir up already fallen snow.

Impact EventImpact Event

• An An impact eventimpact event is the collision of a large meteorite, asteroid, comet, or  is the collision of a large meteorite, asteroid, comet, or other celestial object with the Earth or another planet. Throughout other celestial object with the Earth or another planet. Throughout recorded history, hundreds of minor impact events have been reported, recorded history, hundreds of minor impact events have been reported, with some occurrences causing deaths, injuries, property damage or other with some occurrences causing deaths, injuries, property damage or other significant localised consequences. Impact events have been a plot and significant localised consequences. Impact events have been a plot and background element in science fiction since knowledge of real impacts background element in science fiction since knowledge of real impacts became established in the scientific mainstream.became established in the scientific mainstream.

• Earth has gone through periods of abrupt and catastrophic change, some 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 due to the impact of large asteroids and comets on the planet. A few of these impacts may have caused massive climate change and these impacts may have caused massive climate change and the extinction of large numbers of plant and animal species.the extinction of large numbers of plant and animal species.

• The Moon is widely attributed to a huge impact early in Earth's The Moon is widely attributed to a huge impact early in Earth's history. Impact events earlier in the history of Earth have been credited history. Impact events earlier in the history of Earth have been credited with creative as well as destructive events; it has been proposed that with creative as well as destructive events; it has been proposed that impacting comets delivered the Earth's water, and some have suggested impacting comets delivered the Earth's water, and some have suggested that the origins of life may have been influenced by impacting objects by that the origins of life may have been influenced by impacting objects by bringing organic chemicals or life forms to the Earth's surface, a theory bringing organic chemicals or life forms to the Earth's surface, a theory known as exogenesis.known as exogenesis.

Tropical CycloneTropical Cyclone

• A A tropical cyclonetropical cyclone is a storm system characterized by a low- is a storm system characterized by a low-pressure centre and numerous thunderstorms that produce strong winds pressure centre and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting the ocean is released as the saturated air rises, resulting in in condensationcondensation of water vapour contained in the moist air. They are fueled  of water vapour contained in the moist air. They are fueled by a different heat mechanism than other cyclonic windstorms such by a different heat mechanism than other cyclonic windstorms such as nor'easters ,European windstorms, and polar lows. The characteristic as nor'easters ,European windstorms, and polar lows. The characteristic that separates tropical cyclones from other cyclonic systems is that at any 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 height in the atmosphere, the centre of a tropical cyclone will be warmer than its surroundings; a phenomenon called "warm core" storm systems. than its surroundings; a phenomenon called "warm core" storm systems.

• While tropical cyclones can produce extremely powerful winds and While tropical cyclones can produce extremely powerful winds and torrential rain, they are also able to produce high waves and torrential rain, they are also able to produce high waves and damaging storm surge as well as spawning tornadoes. They develop over 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 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 due to increased surface friction and loss of the warm ocean as an energy source.  source. 

WildfireWildfire

•   A A wildfirewildfire is any uncontrolled fire in combustible vegetation that occurs  is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as in the countryside or a wilderness area. Other names such as brush brush firefire, , bushfirebushfire, , forest forest fire, desert fire, grass fire, hill fire, peat fire, desert fire, grass fire, hill fire, peat fire, vegetation fire, and veldfire may be used to describe the same fire, vegetation fire, and veldfire may be used to describe the same phenomenon depending on the type of vegetation being burned. A wildfire 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 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 spread out from its original source, its potential to change direction unexpectedly, and its ability to jump gaps such as roads, rivers and fire 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 breaks. Wildfires are characterized in terms of the cause of ignition, their physical properties such as speed of propagation, the combustible material physical properties such as speed of propagation, the combustible material present, and the effect of weather on the fire.present, and the effect of weather on the fire.

FamineFamine

• A famineA famine is a widespread scarcity of food, caused by several  is a widespread scarcity of food, caused by several factors including crop failure, overpopulation, or government factors including crop failure, overpopulation, or government policies. This phenomenon is usually accompanied or followed by policies. This phenomenon is usually accompanied or followed by regional malnutrition, starvation, epidemic, and regional malnutrition, starvation, epidemic, and increased mortality. Every continent in the world has experienced increased mortality. Every continent in the world has experienced a period of famine throughout history. Many countries continue to a period of famine throughout history. Many countries continue to have extreme cases of famine. Emergency measures in relieving have extreme cases of famine. Emergency measures in relieving famine primarily include providing deficient micronutrients, such famine primarily include providing deficient micronutrients, such as vitamins and mineral, through fortified sachet powders or as vitamins and mineral, through fortified sachet powders or directly through supplements. The famine relief model directly through supplements. The famine relief model increasingly used by aid groups calls for giving cash or cash increasingly used by aid groups calls for giving cash or cash vouchers to the hungry to pay local farmers instead of buying food vouchers to the hungry to pay local farmers instead of buying food from donor countries, often required by law, as it wastes money from donor countries, often required by law, as it wastes money on transport costs, but more importantly, it perpetuates the cycle on transport costs, but more importantly, it perpetuates the cycle of dependency on foreign imports rather than helping to create of dependency on foreign imports rather than helping to create real local stability through agricultural abundance. Such real local stability through agricultural abundance. Such independence however does rest upon local conditions of soil, independence however does rest upon local conditions of soil, water, temperature and so on.water, temperature and so on.

Solar FlareSolar Flare

• A A solar flaresolar flare is a sudden brightening observed over the Sun surface or the  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 × 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 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 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 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 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 two after the event. The term is also used to refer to similar phenomena in

other stars, where the term stellar flare applies.other stars, where the term stellar flare applies. • Flares occur when accelerated charged particles, mainly electrons, Flares occur when accelerated charged particles, mainly electrons,

interact with the plasma. Scientific research has shown that the interact with the plasma. Scientific research has shown that the phenomenon of magnetic reconnection is responsible for the phenomenon of magnetic reconnection is responsible for the acceleration of the charged particles. On the Sun, magnetic acceleration of the charged particles. On the Sun, magnetic reconnection may happen on solar arcades – a series of closely reconnection may happen on solar arcades – a series of closely occurring loops of magnetic lines of force. These lines of force occurring loops of magnetic lines of force. These lines of force quickly reconnect into a low arcade of loops leaving a helix of quickly reconnect into a low arcade of loops leaving a helix of magnetic field unconnected to the rest of the arcade. magnetic field unconnected to the rest of the arcade.