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143-772: A disaster is an event that causes serious harm to people, buildings, economies, or the environment, and the affected community cannot handle it alone. Natural disasters like avalanches , floods , earthquakes , and wildfires are caused by natural hazards . Human-made disasters like oil spills , terrorist attacks and power outages are caused by people. Nowadays, it is hard to separate natural and human-made disasters because human actions can make natural disasters worse. Climate change also affects how often disasters due to extreme weather hazards happen. Disasters usually hit people in developing countries harder than people in wealthy countries. Over 95% of deaths from disasters happen in low-income countries, and those countries lose
286-472: A slope , such as a hill or mountain. Avalanches can be triggered spontaneously, by factors such as increased precipitation or snowpack weakening, or by external means such as humans, other animals, and earthquakes . Primarily composed of flowing snow and air, large avalanches have the capability to capture and move ice, rocks, and trees. Avalanches occur in two general forms, or combinations thereof: slab avalanches made of tightly packed snow, triggered by
429-536: A vulnerable community . It results from the combination of the hazard and the exposure of a vulnerable society. Nowadays it is hard to distinguish between natural and human-made disasters. The term natural disaster was already challenged in 1976. Human choices in architecture, fire risk, and resource management can cause or worsen natural disasters. Climate change also affects how often disasters due to extreme weather hazards happen. These " climate hazards " are floods, heat waves, wildfires, tropical cyclones, and
572-666: A collapse of an underlying weak snow layer, and loose snow avalanches made of looser snow. After being set off, avalanches usually accelerate rapidly and grow in mass and volume as they capture more snow. If an avalanche moves fast enough, some of the snow may mix with the air, forming a powder snow avalanche . Though they appear to share similarities, avalanches are distinct from slush flows , mudslides , rock slides , and serac collapses. They are also different from large scale movements of ice . Avalanches can happen in any mountain range that has an enduring snowpack. They are most frequent in winter or spring, but may occur at any time of
715-487: A combination of both natural and human factors. All disasters can be regarded as human-made, because of failure to introduce the right emergency management measures. Famines may be caused locally by drought, flood, fire or pestilence. In modern times there is plenty of food globally. Long-lasting local shortages are generally due to government mismanagement, violent conflict, or an economic system that does not distribute food where needed. Complex disasters , where there
858-476: A community is considered a disaster. The international disaster database EM-DAT defines a disaster as “a situation or event that overwhelms local capacity, necessitating a request for external assistance at the national or international level; it is an unforeseen and often sudden event that causes great damage, destruction and human suffering.” The effects of a disaster include all human, material, economic and environmental losses and impacts. UNDRO (1984) defined
1001-418: A component of Los Angeles smog. Haagen-Smit went on to discover that nitrogen oxides from automotive exhausts and gaseous hydrocarbons from cars and oil refineries, exposed to sunlight, were key ingredients in the formation of ozone and photochemical smog. Haagen-Smit worked with Arnold Beckman , who developed various equipment for detecting smog, ranging from an "Apparatus for recording gas concentrations in
1144-424: A critical temperature gradient. Large, angular snow crystals are indicators of weak snow, because such crystals have fewer bonds per unit volume than small, rounded crystals that pack tightly together. Consolidated snow is less likely to slough than loose powdery layers or wet isothermal snow; however, consolidated snow is a necessary condition for the occurrence of slab avalanches , and persistent instabilities within
1287-463: A daily rating of fire danger since September 2003. Indonesia has been ineffective at enforcing legal policies on errant farmers. Since the start of the winter season , heavy smog loaded with pollutants covered major parts of Punjab , especially the city of Lahore , causing breathing problems and disrupting normal traffic. A recent study from 2022 shows that the primary cause of pollution in Lahore
1430-451: A disaster in a more qualitative fashion as: "an event, concentrated in time and space, in which a community undergoes severe danger and incurs such losses to its members and physical appurtenances that the social structure is disrupted and the fulfilment of all or some of the essential functions of the society is prevented." Like other definitions this looks beyond the social aspects of the disaster impacts. It also focuses on losses. This raises
1573-582: A disaster occurs, rather than on response and recovery after the event. DRR and climate change adaptation measures are similar in that they aim to reduce vulnerability of people and places to natural hazards. When a disaster happens, the response includes actions like warning and evacuating people, rescuing those in danger, and quickly providing food, shelter, and medical care. The goal is to save lives and help people recover as quickly as possible. In some cases, national or international help may be needed to support recovery. This can happen, for example, through
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#17327650405901716-559: A drag force that was proportional to the square of the speed of its flow: He and others subsequently derived other formulae that take other factors into account, with the Voellmy-Salm-Gubler and the Perla-Cheng-McClung models becoming most widely used as simple tools to model flowing (as opposed to powder snow) avalanches. Since the 1990s many more sophisticated models have been developed. In Europe much of
1859-463: A fracture at the bottom called the stauchwall. The crown and flank fractures are vertical walls in the snow delineating the snow that was entrained in the avalanche from the snow that remained on the slope. Slabs can vary in thickness from a few centimetres to three metres. Slab avalanches account for around 90% of avalanche-related fatalities. The largest avalanches form turbulent suspension currents known as powder snow avalanches or mixed avalanches,
2002-450: A kind of gravity current . These consist of a powder cloud, which overlies a dense avalanche. They can form from any type of snow or initiation mechanism, but usually occur with fresh dry powder. They can exceed speeds of 300 km/h (190 mph), and masses of 1,000,000 tons; their flows can travel long distances along flat valley bottoms and even uphill for short distances. In contrast to powder snow avalanches, wet snow avalanches are
2145-460: A large quantity of particulate matter; two key components to the creation of smog. However, the smog created as a result of a volcanic eruption is often known as vog to distinguish it as a natural occurrence. The chemical reactions that form smog following a volcanic eruption are different than the reactions that form photochemical smog. The term smog encompasses the effect when a large number of gas-phase molecules and particulate matter are emitted to
2288-607: A long term, lasting from days to years. Experts interpret the recorded data and are able to recognize upcoming ruptures in order to initiate appropriate measures. Such systems (e.g. the monitoring of the Weissmies glacier in Switzerland ) can recognize events several days in advance. Modern radar technology enables the monitoring of large areas and the localization of avalanches at any weather condition, by day and by night. Complex alarm systems are able to detect avalanches within
2431-548: A lot more money compared to richer countries. For example, the damage from natural disasters is 20 times greater in developing countries than in industrialized countries . This is because low-income countries often do not have well-built buildings or good plans to handle emergencies. To reduce the damage from disasters, it is important to be prepared and have fit for purpose infrastructure. Disaster risk reduction (DRR) aims to make communities stronger and better prepared to handle disasters. It focuses on actions to reduce risk before
2574-411: A low velocity suspension of snow and water, with the flow confined to the track surface (McClung, 1999, p. 108). The low speed of travel is due to the friction between the sliding surface of the track and the water saturated flow. Despite the low speed of travel (≈10–40 km/h), wet snow avalanches are capable of generating powerful destructive forces, due to the large mass and density. The body of
2717-452: A major ingredient in the creation of smog in some large cities. The major culprits from transportation sources are carbon monoxide (CO), nitrogen oxides ( NO and NO 2 ), volatile organic compounds, and hydrocarbons (hydrocarbons are the main component of petroleum fuels such as gasoline and diesel fuel ). Transportation emissions also include sulfur dioxides and particulate matter but in much smaller quantities than
2860-400: A number of methods including hand-tossed charges, helicopter-dropped bombs, Gazex concussion lines, and ballistic projectiles launched by air cannons and artillery. Passive preventive systems such as snow fences and light walls can be used to direct the placement of snow. Snow builds up around the fence, especially the side that faces the prevailing winds . Downwind of the fence, snow build-up
3003-413: A persistent weakness in the snowpack. When a slab lying on top of a persistent weakness is loaded by a force greater than the strength of the slab and persistent weak layer, the persistent weak layer can fail and generate an avalanche. Any wind stronger than a light breeze can contribute to a rapid accumulation of snow on sheltered slopes downwind. Wind slabs form quickly and, if present, weaker snow below
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#17327650405903146-400: A point significantly above the freezing point of water, may cause avalanche formation at any time of year. Persistent cold temperatures can either prevent new snow from stabilizing or destabilize the existing snowpack. Cold air temperatures on the snow surface produce a temperature gradient in the snow, because the ground temperature at the base of the snowpack is usually around 0 °C, and
3289-412: A point with only a small amount of snow moving initially; this is typical of wet snow avalanches or avalanches in dry unconsolidated snow. However, if the snow has sintered into a stiff slab overlying a weak layer, then fractures can propagate very rapidly, so that a large volume of snow, possibly thousands of cubic metres, can start moving almost simultaneously. A snowpack will fail when the load exceeds
3432-661: A possible cause of Alzheimer's disease. Researchers at Lancaster University found abundant magnetite nanoparticles in the brain tissue from 37 individuals aged three to 92-years-old who lived in Mexico City and Manchester. This strongly magnetic mineral is toxic and has been implicated in the production of reactive oxygen species (free radicals) in the human brain, which is associated with neurodegenerative diseases including Alzheimer's disease. A study examining 806 women who had babies with birth defects between 1997 and 2006, and 849 women who had healthy babies, found that smog in
3575-585: A reduction in irradiance that hurts both solar photovoltaic production as well as agricultural yield . Smog can form in almost any climate where industries or cities release large amounts of air pollution , such as smoke or gases. However, it is worse during periods of warmer, sunnier weather when the upper air is warm enough to inhibit vertical circulation. It is especially prevalent in geologic basins encircled by hills or mountains. It often stays for an extended period of time over densely populated cities or urban areas and can build up to dangerous levels. For
3718-755: A series of chemical reactions: (4) NO 2 + hv ⟶ O ( 3 P ) + NO {\displaystyle {\ce {NO2 + hv -> O(^3P) + NO}}} , λ < 400 n m {\displaystyle \lambda <400nm} (5) O ( 3 P ) + O 2 + M ⟶ O 3 + M ( heat ) {\displaystyle {\ce {O(^3P) + O2 + M-> O3 + M(heat)}}} (6) O 3 + NO ⟶ NO 2 + O 2 {\displaystyle {\ce {O3 + NO -> NO2 + O2}}} This series of equations
3861-592: A short time in order to close (e.g. roads and rails) or evacuate (e.g. construction sites) endangered areas. An example of such a system is installed on the only access road of Zermatt in Switzerland. Two radars monitor the slope of a mountain above the road. The system automatically closes the road by activating several barriers and traffic lights within seconds such that no people are harmed. Avalanche accidents are broadly differentiated into 2 categories: accidents in recreational settings, and accidents in residential, industrial, and transportation settings. This distinction
4004-417: A start zone where the avalanche originates, a track along which the avalanche flows, and a runout zone where the avalanche comes to rest. The debris deposit is the accumulated mass of the avalanched snow once it has come to rest in the run-out zone. For the image at left, many small avalanches form in this avalanche path every year, but most of these avalanches do not run the full vertical or horizontal length of
4147-415: A storm. Daytime exposure to sunlight will rapidly destabilize the upper layers of the snowpack if the sunlight is strong enough to melt the snow, thereby reducing its hardness. During clear nights, the snowpack can re-freeze when ambient air temperatures fall below freezing, through the process of long-wave radiative cooling, or both. Radiative heat loss occurs when the night air is significantly cooler than
4290-534: A study published in The Lancet , even a very small (5 μg) change in PM2.5 exposure was associated with an increase (18%) in risk of a low birth weight at delivery, and this relationship held even below the current accepted safe levels. Although severe health effects caused by smog are the chief issue, intense air pollution caused by haze from air pollution , dust storm particles, and bush fire smoke, cause
4433-412: A sufficient quantity of airborne snow, this portion of the avalanche can become separated from the bulk of the avalanche and travel a greater distance as a powder snow avalanche. Scientific studies using radar , following the 1999 Galtür avalanche disaster , confirmed the hypothesis that a saltation layer forms between the surface and the airborne components of an avalanche, which can also separate from
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4576-727: A three-month period throughout the Alps in Austria, France, Switzerland, Italy and Germany. This series of avalanches killed around 265 people and was termed the Winter of Terror . A mountain climbing camp on Lenin Peak, in what is now Kyrgyzstan, was wiped out in 1990 when an earthquake triggered a large avalanche that overran the camp. Forty-three climbers were killed. In 1993, the Bayburt Üzengili avalanche killed 60 individuals in Üzengili in
4719-413: A variety of factors such as the snow's shear strength (which is itself dependent upon crystal form) and the configuration of layers and inter-layer interfaces. The snowpack on slopes with sunny exposures is strongly influenced by sunshine . Diurnal cycles of thawing and refreezing can stabilize the snowpack by promoting settlement. Strong freeze-thaw cycles result in the formation of surface crusts during
4862-518: Is a lack of knowledge on the long-term effects of air pollution exposure and the origin of asthma. An experiment was carried out using intense air pollution similar to that of the 1952 Great Smog of London. The results from this experiment concluded that there is a link between early-life pollution exposure that leads to the development of asthma, proposing the ongoing effect of the Great Smog. Modern studies continue to find links between mortality and
5005-403: Is a rigid fence-like structure ( snow fence ) and may be constructed of steel , wood or pre-stressed concrete . They usually have gaps between the beams and are built perpendicular to the slope, with reinforcing beams on the downhill side. Rigid barriers are often considered unsightly, especially when many rows must be built. They are also expensive and vulnerable to damage from falling rocks in
5148-502: Is an increase in coal and other fossil fuel usage to heat homes and buildings. These combustion emissions, together with the lack of pollutant dispersion under inversions, characterize winter smog formation. Smog formation in general relies on both primary and secondary pollutants. Primary pollutants are emitted directly from a source, such as emissions of sulfur dioxide from coal combustion. Secondary pollutants, such as ozone, are formed when primary pollutants undergo chemical reactions in
5291-579: Is called the Starting Point and typically occurs on a 30–45 degree slope. The body of the pathway is called the Track of the avalanche and usually occurs on a 20–30 degree slope. When the avalanche loses its momentum and eventually stops it reaches the Runout Zone. This usually occurs when the slope has reached a steepness that is less than 20 degrees. These degrees are not consistently true due to
5434-461: Is considering imposing a ban on crop burning to reduce pollution in Delhi NCR and an environmental panel has appealed to India's Supreme Court to impose a 30% cess on diesel cars. Joint research between American and Chinese researchers in 2006 concluded that much of Beijing 's pollution comes from surrounding cities and provinces. On average 35–60% of the ozone can be traced to sources outside
5577-424: Is critically sensitive to small variations within the narrow range of meteorological conditions that allow for the accumulation of snow into a snowpack. Among the critical factors controlling snowpack evolution are: heating by the sun, radiational cooling , vertical temperature gradients in standing snow, snowfall amounts, and snow types. Generally, mild winter weather will promote the settlement and stabilization of
5720-536: Is derived from Middle French désastre which comes from Old Italian disastro . This in turn comes from the Ancient Greek pejorative prefix δυσ - ( dus - ) "bad" and ἀστήρ ( aster ), "star". So the word disaster ("bad star" in Greek) comes from an astrological sense of a calamity blamed on the position of planets. Avalanche An avalanche is a rapid flow of snow down
5863-408: Is flat enough to hold snow but steep enough to ski has the potential to generate an avalanche, regardless of the angle. The snowpack is composed of ground-parallel layers that accumulate over the winter. Each layer contains ice grains that are representative of the distinct meteorological conditions during which the snow formed and was deposited. Once deposited, a snow layer continues to evolve under
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6006-510: Is from traffic-related PM (both exhausts and non exhaust sources). Air quality in the Punjab, Pakistan deteriorates markedly during the post- monsoon to winter transition, driven by shifts in weather patterns like alterations in wind, temperature, and boundary layer mixing. In post-moonsoon, anthropogenic emissions from sources like vehicle exhaust , industrial activities, and crop burning impact air quality across Punjab, Pakistan, affecting
6149-470: Is lessened. This is caused by the loss of snow at the fence that would have been deposited and the pickup of the snow that is already there by the wind, which was depleted of snow at the fence. When there is a sufficient density of trees , they can greatly reduce the strength of avalanches. They hold snow in place and when there is an avalanche, the impact of the snow against the trees slows it down. Trees can either be planted or they can be conserved, such as in
6292-504: Is motivated by the observed difference in the causes of avalanche accidents in the two settings. In the recreational setting most accidents are caused by the people involved in the avalanche. In a 1996 study, Jamieson et al. (pages 7–20) found that 83% of all avalanches in the recreational setting were caused by those who were involved in the accident . In contrast, all the accidents in the residential, industrial, and transportation settings were due to spontaneous natural avalanches. Because of
6435-443: Is no single root cause, are more common in developing countries . A specific hazard may also spawn a secondary disaster that increases the impact. A classic example is an earthquake that causes a tsunami . This results in coastal flooding , damaging a nuclear power plant on the coast. The Fukushima nuclear disaster is a case in point. Experts examine these cascading events to see how risks and impacts can amplify and spread. This
6578-427: Is often aggravated by stubble burning in neighboring agricultural areas since the 1980s. The atmospheric pollution levels of Los Angeles , Beijing , Delhi , Lahore , Mexico City , Tehran and other cities are often increased by an inversion that traps pollution close to the ground. The developing smog is usually toxic to humans and can cause severe sickness, a shortened life span, or premature death. Coinage of
6721-404: Is often categorized as being either summer smog or winter smog. Summer smog is primarily associated with the photochemical formation of ozone. During the summer season when the temperatures are warmer and there is more sunlight present, photochemical smog is the dominant type of smog formation. During the winter months when the temperatures are colder, and atmospheric inversions are common, there
6864-520: Is ozone, which is formed when hydrocarbons (HC) and nitrogen oxides (NO x ) combine in the presence of sunlight; nitrogen dioxide (NO 2 ), which is formed as nitric oxide (NO) combines with oxygen (O 2 ) in the air. In addition, when SO 2 and NO x are emitted they eventually are oxidized in the troposphere to nitric acid and sulfuric acid , which, when mixed with water, form the main components of acid rain. All of these harsh chemicals are usually highly reactive and oxidizing. Photochemical smog
7007-541: Is particularly important given the increase in climate risks . Some researchers distinguish between recurring events like seasonal flooding and unpredictable one-off events . Recurring events often carry an estimate of how often they occur. Experts call this the return period . The effects of a disaster include all human, material, economic and environmental losses and impacts. The Emergency Events Database (EM-DAT) records statistics about disasters related to natural hazards. For 2023, EM-DAT recorded 399 disasters, which
7150-420: Is referred to as the photostationary state (PSS). However, because of the presence of Reaction 2 and 3, NO x and ozone are not in a perfectly steady state. By replacing Reaction 6 with Reaction 2 and Reaction 3, the O 3 molecule is no longer destroyed. Therefore, the concentration of ozone keeps increasing throughout the day. This mechanism can escalate the formation of ozone in smog. Other reactions such as
7293-434: Is responsible for an estimated 9,500 premature deaths in the province each year. A 20-year American Cancer Society study found that cumulative exposure also increases the likelihood of premature death from respiratory disease, implying the 8-hour standard may be insufficient. Tiny magnetic particles from air pollution have for the first time been discovered to be lodged in human brains– and researchers think they could be
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#17327650405907436-422: Is successful, it makes communities less the vulnerable because it mitigates the effects of disasters. This means DRR can make risky events fewer and less severe. Climate change can increase climate hazards . So development efforts often consider DRR and climate change adaptation together. Disaster response refers to the actions taken directly before, during, or immediately after a disaster. The objective
7579-402: Is sufficiently unsettled and cold enough for precipitated snow to accumulate into a seasonal snowpack. Continentality , through its potentiating influence on the meteorological extremes experienced by snowpacks, is an important factor in the evolution of instabilities, and consequential occurrence of avalanches faster stabilization of the snowpack after storm cycles. The evolution of the snowpack
7722-541: Is the very harmful impact on a society or community after a natural hazard event. Some examples of natural hazard events include avalanches , droughts , earthquakes , floods , heat waves , landslides , tropical cyclones , volcanic activity and wildfires . Additional natural hazards include blizzards , dust storms , firestorms , hails , ice storms , sinkholes , thunderstorms , tornadoes and tsunamis . A natural disaster can cause loss of life or damage property . It typically causes economic damage. How bad
7865-534: Is therefore considered to be a problem of modern industrialization. It is present in all modern cities, but it is more common in cities with sunny, warm, dry climates and a large number of motor vehicles. Because it travels with the wind, it can affect sparsely populated areas as well. The composition and chemical reactions involved in photochemical smog were not understood until the 1950s. In 1948, flavor chemist Arie Haagen-Smit adapted some of his equipment to collect chemicals from polluted air, and identified ozone as
8008-803: Is to save lives, ensure health and safety, and meet the subsistence needs of the people affected. It includes warning and evacuation, search and rescue , providing immediate assistance, assessing damage, continuing assistance, and the immediate restoration or construction of infrastructure . An example of this would be building provisional storm drains or diversion dams . Emergency response aims to provide immediate help to keep people alive, improve their health and support their morale. It can involve specific but limited aid, such as helping refugees with transport, temporary shelter, and food. Or it can involve establishing semi-permanent settlements in camps and other locations. It may also involve initial repairs to damage to infrastructure, or diverting it. The word disaster
8151-424: Is usual to divide disasters into natural or human-made. Recently the divide between natural, man-made and man-accelerated disasters has become harder to draw. Some manufactured disasters such as smog and acid rain have been wrongly attributed to nature. Disasters with links to natural hazards are commonly called natural disasters . However experts have questioned this term for a long time. A natural disaster
8294-461: The Agreement on Transboundary Haze Pollution was signed between all ASEAN nations. ASEAN formed a Regional Haze Action Plan (RHAP) and established a co-ordination and support unit (CSU). RHAP, with the help of Canada , established a monitoring and warning system for forest/vegetation fires and implemented a Fire Danger Rating System (FDRS). The Malaysian Meteorological Department (MMD) has issued
8437-490: The Indo-Gangetic Plain (IGP) worsens significantly due to shifts in weather patterns, such as changes in wind, temperature, and boundary layer mixing. The impact of emissions from both biomass burning and urban activities has intensified, leading to a rise in aerosols mainly particulate matters. The nearby Himalayan region is also affected, where mountainous topography trap air pollutants and increase
8580-787: The Malacca Straits is in October 2006, and was caused by smoke from fires in Indonesia being blown across the Straits of Malacca by south-westerly winds. A similar haze has occurred in June 2013, with the PSI setting a new record in Singapore on 21 June at 12pm with a reading of 401, which is in the "Hazardous" range. The Association of Southeast Asian Nations (ASEAN) reacted. In 2002,
8723-533: The Middle Ages . London, in particular, was notorious up through the mid-20th century for its coal-caused smogs, which were nicknamed " pea-soupers ". Air pollution of this type is still a problem in areas that generate significant smoke from burning coal. The emissions from coal combustion are one of the main causes of air pollution in China . Especially during autumn and winter when coal-fired heating ramps up,
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#17327650405908866-694: The Rogers Pass avalanche in British Columbia , Canada. During World War I , an estimated 40,000 to 80,000 soldiers died as a result of avalanches during the mountain campaign in the Alps at the Austrian-Italian front, many of which were caused by artillery fire. Some 10,000 men, from both sides, died in avalanches in December 1916. In the northern hemisphere winter of 1950–1951 approximately 649 avalanches were recorded in
9009-585: The San Joaquin Valley area of California was linked to two types of neural tube defects : spina bifida (a condition involving, among other manifestations, certain malformations of the spinal column ), and anencephaly (the underdevelopment or absence of part or all of the brain, which if not fatal usually results in profound impairment). An emerging cohort study in China linked early-life smog exposure to an increased risk for adverse pregnancy outcomes, in particular oxidative stress. According to
9152-502: The angle of repose , depends on a variety of factors, such as crystal form and moisture content. Some forms of drier and colder snow will only stick to shallower slopes, while wet and warm snow can bond to very steep surfaces. In coastal mountains, such as the Cordillera del Paine region of Patagonia , deep snowpacks collect on vertical and even overhanging rock faces. The slope angle that can allow moving snow to accelerate depends on
9295-496: The avalanche dam on Mount Stephen in Kicking Horse Pass , have been constructed to protect people and property by redirecting the flow of avalanches. Deep debris deposits from avalanches will collect in catchments at the terminus of a run out, such as gullies and river beds. Slopes flatter than 25 degrees or steeper than 60 degrees typically have a lower incidence of avalanches. Human-triggered avalanches have
9438-422: The 19th century to the mid-20th century, where it was commonly known as a London particular or London fog . This kind of visible air pollution is composed of nitrogen oxides , sulfur oxide , ozone , smoke and other particulates . Man-made smog is derived from coal combustion emissions, vehicular emissions, industrial emissions, forest and agricultural fires and photochemical reactions of these emissions. Smog
9581-509: The Khumbu Icefall), triggering a movement of broken ice chunks. The resulting movement is more analogous to a rockfall or a landslide than a snow avalanche. They are typically very difficult to predict and almost impossible to mitigate. As an avalanche moves down a slope it follows a certain pathway that is dependent on the slope's degree of steepness and the volume of snow/ice involved in the mass movement . The origin of an avalanche
9724-517: The SAMOS-AT avalanche simulation software and the RAMMS software. Preventative measures are employed in areas where avalanches pose a significant threat to people, such as ski resorts , mountain towns, roads, and railways. There are several ways to prevent avalanches and lessen their power and develop preventative measures to reduce the likelihood and size of avalanches by disrupting the structure of
9867-474: The United States. In 2001 it was reported that globally an average of 150 people die each year from avalanches. Three of the deadliest recorded avalanches have killed over a thousand people each. Doug Fesler and Jill Fredston developed a conceptual model of the three primary elements of avalanches: terrain, weather, and snowpack. Terrain describes the places where avalanches occur, weather describes
10010-487: The air quality issues specifically in northern India. Delhi is the most polluted city in the world and according to one estimate, air pollution causes the death of about 10,500 people in Delhi every year. During 2013–14, peak levels of fine particulate matter (PM) in Delhi increased by about 44%, primarily due to high vehicular and industrial emissions, construction work and crop burning in adjoining states. Delhi has
10153-408: The ambient air temperature can be much colder. When a temperature gradient greater than 10 °C change per vertical meter of snow is sustained for more than a day, angular crystals called depth hoar or facets begin forming in the snowpack because of rapid moisture transport along the temperature gradient. These angular crystals, which bond poorly to one another and the surrounding snow, often become
10296-406: The amount of O 3 that can be produced from its photolysis (reaction 4). HNO 3 , nitric acid, is a sticky compound that can easily be removed onto surfaces (dry deposition) or dissolved in water and be rained out (wet deposition). Both ways are common in the atmosphere and can efficiently remove radicals and nitrogen dioxide. An erupting volcano can emit high levels of sulfur dioxide along with
10439-412: The amount of produced smoke at times forces some Chinese cities to close down roads, schools or airports. One prominent example for this was China's Northeastern city of Harbin in 2013 . Traffic emissions – such as from trucks , buses , and automobiles – also contribute to the formation of smog. Airborne by-products from vehicle exhaust systems and air conditioning cause air pollution and are
10582-1137: The atmosphere" patented on 7 October 1952, to "air quality monitoring vans" for use by government and industry. During the morning rush hour, a high concentration of nitric oxide and hydrocarbons are emitted to the atmosphere, mostly via on-road traffic but also from industrial sources. Some hydrocarbons are rapidly oxidized by OH· and form peroxy radicals, which convert nitric oxide (NO) to nitrogen dioxide (NO 2 ). (1) R ⋅ + O 2 + M ⟶ RO 2 ⋅ + M {\displaystyle {\ce {R{.}+ O2 + M -> RO2{.}+ M}}} (2) RO 2 ⋅ + NO ⟶ NO 2 + RO ⋅ {\displaystyle {\ce {RO2{.}+ NO -> NO2 + RO{.}}}} (3) HO 2 ⋅ + NO ⟶ NO 2 + OH ⋅ {\displaystyle {\ce {HO2{.}+ NO -> NO2 + OH{.}}}} Nitrogen dioxide (NO 2 ) and nitric oxide (NO) further react with ozone (O 3 ) in
10725-531: The atmosphere, creating a visible haze . The event causing a large number of emissions can vary but still result in the formation of smog. Plants are another natural source of hydrocarbons that could undergo reactions in the atmosphere and produce smog. Globally both plants and soil contribute a substantial amount to the production of hydrocarbons, mainly by producing isoprene and terpenes . Hydrocarbons released by plants can often be more reactive than man-made hydrocarbons. For example when plants release isoprene,
10868-495: The atmosphere, which leaves airborne particles and ground-level ozone . Photochemical smog depends on primary pollutants as well as the formation of secondary pollutants. These primary pollutants include nitrogen oxides , particularly nitric oxide (NO) and nitrogen dioxide (NO 2 ), and volatile organic compounds . The relevant secondary pollutants include peroxylacyl nitrates (PAN), tropospheric ozone , and aldehydes . An important secondary pollutant for photochemical smog
11011-465: The atmosphere. Photochemical smog, as found for example in Los Angeles, is a type of air pollution derived from vehicular emission from internal combustion engines and industrial fumes. These pollutants react in the atmosphere with sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog . In certain other cities, such as Delhi, smog severity
11154-537: The author claims to have invented the word: "The 'Smog' – a word I have invented, combined of smoke and fog, to designate the London atmosphere..." Coal fire can emit significant clouds of smoke that contribute to the formation of winter smog. Coal fires can be used to heat individual buildings or to provide energy in a power-producing plant. Air pollution from this source has been reported in England since
11297-426: The avalanche's path to slow it down. Finally, along transportation corridors, large shelters, called snow sheds , can be built directly in the slide path of an avalanche to protect traffic from avalanches. Warning systems can detect avalanches which develop slowly, such as ice avalanches caused by icefalls from glaciers. Interferometric radars, high-resolution cameras, or motion sensors can monitor instable areas over
11440-399: The average maximum temperature in Delhi during winters has declined notably since 1998 due to rising air pollution. Environmentalists have criticized the Delhi government for not doing enough to curb air pollution and to inform people about air quality issues. Most of Delhi's residents are unaware of alarming levels of air pollution in the city and the health risks associated with it. Since
11583-401: The building of a ski resort, to reduce the strength of avalanches. In turn, socio-environmental changes can influence the occurrence of damaging avalanches: some studies linking changes in land-use/land-cover patterns and the evolution of snow avalanche damage in mid latitude mountains show the importance of the role played by vegetation cover, that is at the root of the increase of damage when
11726-432: The bulk of the avalanche. Driving an avalanche is the component of the avalanche's weight parallel to the slope; as the avalanche progresses any unstable snow in its path will tend to become incorporated, so increasing the overall weight. This force will increase as the steepness of the slope increases, and diminish as the slope flattens. Resisting this are a number of components that are thought to interact with each other:
11869-480: The city. However, according to several authors, most of these gains have been lost, especially due to stubble burning , rise in market share of diesel cars and a considerable decline in bus ridership. According to CUE and System of Air Quality Weather Forecasting and Research (SAFER), burning of agricultural waste in nearby Punjab, Haryana and Uttar Pradesh regions results in severe intensification of smog over Delhi. The state government of adjoining Uttar Pradesh
12012-530: The city. Shandong Province and Tianjin Municipality have a "significant influence on Beijing's air quality", partly due to the prevailing south/southeasterly flow during the summer and the mountains to the north and northwest. In December 2005, schools and public offices were forced to close in Tehran and 1,600 people were taken to hospital, in a severe smog blamed largely on unfiltered car exhaust. In
12155-531: The conversion of Delhi's fleet of buses and taxis to run on CNG and banned the use of leaded petrol in 1998. In 2003, Delhi won the United States Department of Energy 's first 'Clean Cities International Partner of the Year' award for its "bold efforts to curb air pollution and support alternative fuel initiatives". The Delhi Metro has also been credited for significantly reducing air pollutants in
12298-405: The damage is depends on how well people are prepared for disasters and how strong the buildings, roads, and other structures are. Scholars have been saying that the term natural disaster is unsuitable and should be abandoned. Instead, the simpler term disaster could be used. At the same time the type of hazard would be specified. A disaster happens when a natural or human-made hazard impacts
12441-409: The depths, crystal forms, and layering of the seasonal snowpack. Slab avalanches are formed frequently in snow that has been deposited, or redeposited by wind. They have the characteristic appearance of a block (slab) of snow cut out from its surroundings by fractures. Elements of slab avalanches include a crown fracture at the top of the start zone, flank fractures on the sides of the start zones, and
12584-693: The difference in the causes of avalanche accidents, and the activities pursued in the two settings, avalanche and disaster management professionals have developed two related preparedness, rescue, and recovery strategies for each of the settings. Two avalanches occurred in March 1910 in the Cascade and Selkirk Mountain ranges; on 1 March the Wellington avalanche killed 96 in Washington state , United States. Three days later 62 railroad workers were killed in
12727-532: The early 20th century, notably the work of Professor Lagotala in preparation for the 1924 Winter Olympics in Chamonix . His method was developed by A. Voellmy and popularised following the publication in 1955 of his Ueber die Zerstoerungskraft von Lawinen (On the Destructive Force of Avalanches). Voellmy used a simple empirical formula, treating an avalanche as a sliding block of snow moving with
12870-534: The fact that each avalanche is unique depending on the stability of the snowpack that it was derived from as well as the environmental or human influences that triggered the mass movement. People caught in avalanches can die from suffocation , trauma, or hypothermia . From "1950–1951 to 2020–2021" there were 1,169 people who died in avalanches in the United States. For the 11-year period ending April 2006, 445 people died in avalanches throughout North America. On average, 28 people die in avalanches every winter in
13013-672: The fires, which they use to clear tracts of land for further plantings. Those fires mainly affect Brunei , Indonesia , Philippines , Malaysia , Singapore and Thailand , and occasionally Guam and Saipan . The economic losses of the fires in 1997 have been estimated at more than US$ 9 billion. This includes damages in agriculture production, destruction of forest lands, health, transportation, tourism, and other economic endeavours. Not included are social, environmental, and psychological problems and long-term health effects. The second-latest bout of haze to occur in Malaysia , Singapore and
13156-452: The flow of a wet snow avalanche can plough through soft snow, and can scour boulders, earth, trees, and other vegetation; leaving exposed and often scored ground in the avalanche track. Wet snow avalanches can be initiated from either loose snow releases, or slab releases, and only occur in snowpacks that are water saturated and isothermally equilibrated to the melting point of water. The isothermal characteristic of wet snow avalanches has led to
13299-460: The friction between the avalanche and the surface beneath; friction between the air and snow within the fluid; fluid-dynamic drag at the leading edge of the avalanche; shear resistance between the avalanche and the air through which it is passing, and shear resistance between the fragments within the avalanche itself. An avalanche will continue to accelerate until the resistance exceeds the forward force. Attempts to model avalanche behaviour date from
13442-508: The general public. 8 hour average ozone concentrations of 85 to 104 ppbv are described as "Unhealthy for Sensitive Groups", 105 ppbv to 124 ppbv as "unhealthy" and 125 ppb to 404 ppb as "very unhealthy". The "very unhealthy" range for some other pollutants are: 355 μg m – 424 μg m for PM10 ; 15.5 ppm – 30.4ppm for CO and 0.65 ppm – 1.24 ppm for NO 2 . In 2016, the Ontario Medical Association announced that smog
13585-470: The greatest incidence when the snow's angle of repose is between 35 and 45 degrees; the critical angle, the angle at which human-triggered avalanches are most frequent, is 38 degrees. When the incidence of human triggered avalanches is normalized by the rates of recreational use, however, hazard increases uniformly with slope angle, and no significant difference in hazard for a given exposure direction can be found. The rule of thumb is: A slope that
13728-866: The ground surface beneath the snowpack influences the stability of the snowpack, either being a source of strength or weakness. Avalanches are unlikely to form in very thick forests, but boulders and sparsely distributed vegetation can create weak areas deep within the snowpack through the formation of strong temperature gradients. Full-depth avalanches (avalanches that sweep a slope virtually clean of snow cover) are more common on slopes with smooth ground, such as grass or rock slabs. Generally speaking, avalanches follow drainages down-slope, frequently sharing drainage features with summertime watersheds. At and below tree line , avalanche paths through drainages are well defined by vegetation boundaries called trim lines , which occur where avalanches have removed trees and prevented regrowth of large vegetation. Engineered drainages, such as
13871-411: The highest level of the airborne particulate matter, PM2.5 considered most harmful to health, with 153 micrograms. Rising air pollution level has significantly increased lung-related ailments (especially asthma and lung cancer) among Delhi's children and women. The dense smog in Delhi during winter season results in major air and rail traffic disruptions every year. According to Indian meteorologists,
14014-508: The influence of the meteorological conditions that prevail after deposition. For an avalanche to occur, it is necessary that a snowpack have a weak layer (or instability) below a slab of cohesive snow. In practice the formal mechanical and structural factors related to snowpack instability are not directly observable outside of laboratories, thus the more easily observed properties of the snow layers (e.g. penetration resistance, grain size, grain type, temperature) are used as index measurements of
14157-478: The initial onset of the disaster. These could be the effects of diseases such as cholera or dysentery arising from the disaster. This definition is still commonly used. However it is limited to the number of deaths, injuries, and damage in money terms. The scale of a disaster matters. Small-scale disasters only affect local communities but need help beyond the affected community. Large-scale disasters affect wider society and need national or international help. It
14300-498: The isoprene reacts very quickly in the atmosphere with hydroxyl radicals. These reactions produce hydroperoxides which increase ozone formation. Smog is a serious problem in many cities and continues to harm human health. Ground-level ozone , sulfur dioxide , nitrogen dioxide and carbon monoxide are especially harmful for senior citizens, children, and people with heart and lung conditions such as emphysema , bronchitis , and asthma . It can inflame breathing passages, decrease
14443-457: The late 1990s, massive immigration to Ulaanbaatar from the countryside began. An estimated 150,000 households, mainly living in traditional Mongolian gers on the outskirts of Ulaanbaatar, burn wood and coal (some poor families burn even car tires and trash) to heat themselves during the harsh winter, which lasts from October to April, since these outskirts are not connected to the city's central heating system. A temporary solution to decrease smog
14586-712: The like. Human-made disasters are serious harmful events caused by human actions and social processes. Technological hazards also fall into this category. That is because they result in human-instigated disasters. Human-made hazards are sometimes called anthropogenic hazards. Examples include criminality , social unrest , crowd crushes , fires , transport accidents , industrial accidents , power outages, oil spills , terrorist attacks , and nuclear explosions / nuclear radiation . Catastrophic climate change , nuclear war , and bioterrorism also fall into this category. Climate change and environmental degradation are sometimes called socio-natural hazards. These are hazards involving
14729-413: The likelihood of an avalanche. Observation and experience has shown that newly fallen snow requires time to bond with the snow layers beneath it, especially if the new snow falls during very cold and dry conditions. If ambient air temperatures are cold enough, shallow snow above or around boulders, plants, and other discontinuities in the slope, weakens from rapid crystal growth that occurs in the presence of
14872-450: The local humidity, water vapour flux, temperature and heat flux. The top of the snowpack is also extensively influenced by incoming radiation and the local air flow. One of the aims of avalanche research is to develop and validate computer models that can describe the evolution of the seasonal snowpack over time. A complicating factor is the complex interaction of terrain and weather, which causes significant spatial and temporal variability of
15015-599: The lowest risk of feeling the consequences. As of 2019, countries with the highest vulnerability per capita release the lowest amount of emissions per capita, and yet still experience the most heightened droughts and extreme precipitation. Disaster risk reduction aims to make disasters less likely to happen. The approach, also called DRR or disaster risk management, also aims to make disasters less damaging when they do occur. DRR aims to make communities stronger and better prepared to handle disasters. In technical terms, it aims to make them more resilient or less vulnerable. When DRR
15158-417: The lungs' working capacity, cause shortness of breath, pain when inhaling deeply, wheezing, and coughing. It can cause eye and nose irritation and it dries out the protective membranes of the nose and throat and interferes with the body's ability to fight infection, increasing susceptibility to illness. Hospital admissions and respiratory deaths often increase during periods when ozone levels are high. There
15301-526: The mechanical properties of the snow (e.g. tensile strength , friction coefficients, shear strength , and ductile strength ). This results in two principal sources of uncertainty in determining snowpack stability based on snow structure: First, both the factors influencing snow stability and the specific characteristics of the snowpack vary widely within small areas and time scales, resulting in significant difficulty extrapolating point observations of snow layers across different scales of space and time. Second,
15444-421: The meteorological conditions that create the snowpack, and snowpack describes the structural characteristics of snow that make avalanche formation possible. Avalanche formation requires a slope shallow enough for snow to accumulate but steep enough for the snow to accelerate once set in motion by the combination of mechanical failure (of the snowpack) and gravity. The angle of the slope that can hold snow, called
15587-612: The mid-1990s, Delhi has undertaken some measures to curb air pollution – Delhi has the third highest quantity of trees among Indian cities and the Delhi Transport Corporation operates the world's largest fleet of environmentally friendly compressed natural gas (CNG) buses. In 1996, the Centre for Science and Environment (CSE) started a public interest litigation in the Supreme Court of India that ordered
15730-419: The need for emergency response as an aspect of the disaster. It does not set out quantitative thresholds or scales for damage, death, or injury. A study in 1969 defined major disasters as conforming to the following criteria, based on the amount of deaths or damage: At least 100 people dead, at least 100 people injured, or at least $ 1 million damage. This definition includes indirect losses of life caused after
15873-414: The new snow has insufficient time to bond to underlying snow layers. Rain has a similar effect. In the short term, rain causes instability because, like a heavy snowfall, it imposes an additional load on the snowpack and once rainwater seeps down through the snow, acts as a lubricant, reducing the natural friction between snow layers that holds the snowpack together. Most avalanches happen during or soon after
16016-478: The newspaper stated that "Dr. Des Voeux did a public service in coining a new word for the London fog." However, the term appeared twenty-five years earlier than Voeux's paper, in the Santa Cruz & Monterey Illustrated Handbook published in 1880 and also appears in print in a column quoting from the book in the 3 July 1880, Santa Cruz Weekly Sentinel. On 17 December 1881, in the publication Sporting Times,
16159-427: The night and of unstable surface snow during the day. Slopes in the lee of a ridge or of another wind obstacle accumulate more snow and are more likely to include pockets of deep snow, wind slabs , and cornices , all of which, when disturbed, may result in avalanche formation. Conversely, the snowpack on a windward slope is often much shallower than on a lee slope. Avalanches and avalanche paths share common elements:
16302-681: The number of deaths was much higher than the 20-year average of 64,148, the number affected was much lower than the 20-year average of 175.5 million. According to a UN report, 91% of deaths from hazards from 1970 to 2019 occurred in developing countries. These countries already have higher vulnerability and lower resilience to these events, which exacerbates the effects of the hazards. Hazards such as droughts , floods , and cyclones are naturally occurring phenomena. However, climate change has caused these hazards to become more unreliable, frequent and severe. They thus contribute to disaster risks. Countries contributing most to climate change are often at
16445-408: The past few years, cities in northern India have been covered in a thick layer of winter smog. The situation has turned quite drastic in the national capital, Delhi . This smog is caused by the collection of particulate matter (a very fine type of dust and toxic gases) in the air due to stagnant movement of air during winters. Moreover, during the post-monsoon to winter transition, air quality in
16588-407: The path. The frequency with which avalanches form in a given area is known as the return period . The start zone of an avalanche must be steep enough to allow snow to accelerate once set in motion, additionally convex slopes are less stable than concave slopes because of the disparity between the tensile strength of snow layers and their compressive strength . The composition and structure of
16731-409: The photooxidation of formaldehyde (HCHO), a common secondary pollutant, can also contribute to the increased concentration of ozone and NO 2 . Photochemical smog is more prevalent during summer days since incident solar radiation fluxes are high, which favors the formation of ozone (reactions 4 and 5). The presence of a temperature inversion layer is another important factor. That is because it prevents
16874-428: The pollutants mentioned previously. The nitrogen oxides and volatile organic compounds can undergo a series of chemical reactions with sunlight, heat, ammonia , moisture, and other compounds to form the noxious vapors, ground level ozone , and particles that comprise smog. Photochemical smog, often referred to as "summer smog", is the chemical reaction of sunlight, nitrogen oxides and volatile organic compounds in
17017-682: The presence of smog. One study, published in Nature magazine , found that smog episodes in the city of Jinan, a large city in eastern China, during 2011–15, were associated with a 5.87% (95% CI 0.16–11.58%) increase in the rate of overall mortality. This study highlights the effect of exposure to air pollution on the rate of mortality in China. A similar study in Xi'an found an association between ambient air pollution and increased mortality associated with respiratory diseases. The U.S. EPA has developed an air quality index to help explain air pollution levels to
17160-414: The prevention of development in these areas. To mitigate the effect of avalanches the construction of artificial barriers can be very effective in reducing avalanche damage. There are several types: One kind of barrier ( snow net ) uses a net strung between poles that are anchored by guy wires in addition to their foundations. These barriers are similar to those used for rockslides . Another type of barrier
17303-550: The protective forest is deforested (because of demographic growth, intensive grazing and industrial or legal causes), and at the root of the decrease of damage because of the transformation of a traditional land-management system based on overexploitation into a system based on land marginalization and reforestation, something that has happened mainly since the mid-20th century in mountain environments of developed countries. In many areas, regular avalanche tracks can be identified and precautions can be taken to minimize damage, such as
17446-468: The province of Bayburt , Turkey . Smog Smog , or smoke fog , is a type of intense air pollution . The word "smog" was coined in the early 20th century, and is a portmanteau of the words smoke and fog to refer to smoky fog due to its opacity, and odor. The word was then intended to refer to what was sometimes known as pea soup fog , a familiar and serious problem in London from
17589-804: The recent work was carried out as part of the SATSIE (Avalanche Studies and Model Validation in Europe) research project supported by the European Commission which produced the leading-edge MN2L model, now in use with the Service Restauration des Terrains en Montagne (Mountain Rescue Service) in France, and D2FRAM (Dynamical Two-Flow-Regime Avalanche Model), which was still undergoing validation as of 2007. Other known models are
17732-407: The region by 90–100%. Doctors advised residents to stay indoors and wear facemasks outside. In 1306, concerns over air pollution were sufficient for Edward I to (briefly) ban coal fires in London. In 1661, John Evelyn 's Fumifugium suggested burning fragrant wood instead of mineral coal, which he believed would reduce coughing. The " Ballad of Gresham College " the same year describes how
17875-409: The relationship between readily observable snowpack characteristics and the snowpack's critical mechanical properties has not been completely developed. While the deterministic relationship between snowpack characteristics and snowpack stability is still a matter of ongoing scientific study, there is a growing empirical understanding of the snow composition and deposition characteristics that influence
18018-458: The secondary term of isothermal slides found in the literature (for example in Daffern, 1999, p. 93). At temperate latitudes wet snow avalanches are frequently associated with climatic avalanche cycles at the end of the winter season, when there is significant daytime warming. An ice avalanche occurs when a large piece of ice, such as from a serac or calving glacier, falls onto ice (such as
18161-416: The slab may not have time to adjust to the new load. Even on a clear day, wind can quickly load a slope with snow by blowing snow from one place to another. Top-loading occurs when wind deposits snow from the top of a slope; cross-loading occurs when wind deposits snow parallel to the slope. When a wind blows over the top of a mountain, the leeward, or downwind, side of the mountain experiences top-loading, from
18304-415: The smoke "does our lungs and spirits choke, Our hanging spoil, and rust our iron." Severe episodes of smog continued in the 19th and 20th centuries, mainly in the winter, and were nicknamed "pea-soupers," from the phrase "as thick as pea soup". The Great Smog of 1952 darkened the streets of London and killed approximately 4,000 people in the short time of four days (a further 8,000 died from its effects in
18447-429: The snowpack can hide below well-consolidated surface layers. Uncertainty associated with the empirical understanding of the factors influencing snow stability leads most professional avalanche workers to recommend conservative use of avalanche terrain relative to current snowpack instability. Avalanches only occur in a standing snowpack. Typically winter seasons at high latitudes, high altitudes, or both have weather that
18590-423: The snowpack, and the heat stored in the snow is re-radiated into the atmosphere. When a slab avalanche forms, the slab disintegrates into increasingly smaller fragments as the snow travels downhill. If the fragments become small enough the outer layer of the avalanche, called a saltation layer, takes on the characteristics of a fluid . When sufficiently fine particles are present they can become airborne and, given
18733-460: The snowpack, such as melting due to solar radiation, is the second-largest cause of natural avalanches. Other natural causes include rain, earthquakes, rockfall, and icefall. Artificial triggers of avalanches include skiers, snowmobiles, and controlled explosive work. Contrary to popular belief, avalanches are not triggered by loud sound; the pressure from sound is orders of magnitude too small to trigger an avalanche. Avalanche initiation can start at
18876-479: The snowpack, while passive measures reinforce and stabilize the snowpack in situ . The simplest active measure is repeatedly traveling on a snowpack as snow accumulates; this can be by means of boot-packing, ski-cutting, or machine grooming . Explosives are used extensively to prevent avalanches, by triggering smaller avalanches that break down instabilities in the snowpack, and removing overburden that can result in larger avalanches. Explosive charges are delivered by
19019-402: The snowpack; conversely, very cold, windy, or hot weather will weaken the snowpack. At temperatures close to the freezing point of water, or during times of moderate solar radiation, a gentle freeze-thaw cycle will take place. The melting and refreezing of water in the snow strengthens the snowpack during the freezing phase and weakens it during the thawing phase. A rapid rise in temperature, to
19162-401: The strength. The load is straightforward; it is the weight of the snow. However, the strength of the snowpack is much more difficult to determine and is extremely heterogeneous. It varies in detail with properties of the snow grains, size, density, morphology, temperature, water content; and the properties of the bonds between the grains. These properties may all metamorphose in time according to
19305-503: The term "smog" has been attributed to Henry Antoine Des Voeux in his 1905 paper, "Fog and Smoke" for a meeting of the Public Health Congress . The 26 July 1905 edition of the London newspaper Daily Graphic quoted Des Voeux, "He said it required no science to see that there was something produced in great cities which was not found in the country, and that was smoky fog, or what was known as 'smog'." The following day
19448-421: The top to the bottom of that lee slope. When the wind blows across a ridge that leads up the mountain, the leeward side of the ridge is subject to cross-loading. Cross-loaded wind-slabs are usually difficult to identify visually. Snowstorms and rainstorms are important contributors to avalanche danger. Heavy snowfall will cause instability in the existing snowpack, both because of the additional weight and because
19591-554: The vertical convective mixing of the air and thus allows the pollutants, including ozone, to accumulate near the ground level, which again favors the formation of photochemical smog. There are certain reactions that can limit the formation of O 3 in smog. The main limiting reaction in polluted areas is: (7) NO 2 + OH ⋅ + M ⟶ HNO 3 + M {\displaystyle {\ce {NO2 + OH{.}+ M -> HNO3 + M}}} This reaction removes NO 2 which limits
19734-449: The warmer months. In addition to industrially manufactured barriers, landscaped barriers, called avalanche dams stop or deflect avalanches with their weight and strength. These barriers are made out of concrete, rocks, or earth. They are usually placed right above the structure, road, or railway that they are trying to protect, although they can also be used to channel avalanches into other barriers. Occasionally, earth mounds are placed in
19877-473: The work of humanitarian organizations . The UN defines a disaster as "a serious disruption of the functioning of a community or a society at any scale". It results from hazards in places where people live in exposed or vulnerable conditions. Some human failures make communities vulnerable to climate hazards . These are poor planning or development, or a lack of preparation. Disasters are events that have an effect on people. A hazard that overwhelms or injures
20020-525: The world, according to a December 2009 World Bank report. The Asian Development Bank (ADB) estimates that health costs related to this air pollution account for as much as 4 percent of Mongolia's GDP. Smog is a regular problem in Southeast Asia caused by land and forest fires in Indonesia , especially Sumatra and Kalimantan , although the term haze is preferred in describing the problem. Farmers and plantation owners are usually responsible for
20163-485: The year. In mountainous areas, avalanches are among the most serious natural hazards to life and property, so great efforts are made in avalanche control . There are many classification systems for the different forms of avalanches. Avalanches can be described by their size, destructive potential, initiation mechanism, composition, and dynamics . Most avalanches occur spontaneously during storms under increased load due to snowfall and/or erosion . Metamorphic changes in
20306-513: Was higher than the 20-year average of 369. Between 2016 and 2020 the total reported economic losses amounted to $ 293 billion. This figure is likely to be an underestimation. It is very challenging to measure the costs of disasters accurately, and many countries lack the resources and technical capacity to do so. Over the 40-year period from 1980 to 2020 losses were estimated at $ 5.2 trillion. In 2023, natural hazard-related disasters resulted in 86,473 fatalities and affected 93.1 million people. Whilst
20449-405: Was proposed in the form of stoves with improved efficiency, although with no visible results. Coal-fired ger stoves release high levels of ash and other particulate matter (PM). When inhaled, these particles can settle in the lungs and respiratory tract and cause health problems. At two to 10 times above Mongolian and international air quality standards, Ulaanbaatar's PM rates are among the worst in
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