Problems of the Russian plain: earthquake, dust storms. Dust storm
Sandstorm - view from an airplane
Dust (sand) storm- an atmospheric phenomenon in the form of the transfer of large quantities of dust (soil particles, grains of sand) by the wind from the earth's surface in a layer several meters high with a noticeable deterioration in horizontal visibility (usually at a level of 2 m it ranges from 1 to 9 km, but in some cases it can decrease to several hundred and even up to several tens of meters). In this case, dust (sand) rises into the air and, at the same time, dust settles over a large area. Depending on the color of the soil in a given region, distant objects acquire a grayish, yellowish or reddish tint. It usually occurs when the soil surface is dry and the wind speed is 10 m/s or more.
Often occurs during the warm season in desert and semi-desert regions. In addition to the “actual” dust storm, in some cases dust from deserts and semi-deserts can remain in the atmosphere for a long time and reach almost anywhere in the world in the form of a dusty haze.
Dust storms occur less frequently in steppe regions, very rarely in forest-steppe and even forest regions (in the last two zones, a dust storm occurs more often in the summer during severe drought). In steppe and (less often) forest-steppe regions, dust storms usually occur in early spring, after a winter with little snow and a dry autumn, but sometimes they occur even in winter, in combination with blizzards.
When a certain threshold of wind speed is exceeded (depending on the mechanical composition of the soil and its moisture), particles of dust and sand come off the surface and are transported by saltation and suspension, causing soil erosion.
Dusty (sandy) drifting snow - the transfer of dust (soil particles, grains of sand) by the wind from the earth's surface in a layer 0.5-2 m high, which does not lead to a noticeable deterioration in visibility (if there are no other atmospheric phenomena, horizontal visibility at a level of 2 m is 10 km and more ). It usually occurs when the soil surface is dry and the wind speed is 6-9 m/s or more.
Causes
With an increase in the strength of the wind flow passing over loose particles, the latter begin to vibrate and then “jump”. When these particles repeatedly strike the ground, they create fine dust that rises in suspension.
Recent research suggests that the initial saltation of sand grains by friction induces electrostatic field . The jumping particles acquire a negative charge, which releases even more particles. This process captures twice as many particles as previous theories predict.
Particles are released mainly due to dry soil and increased wind. Gust fronts can occur due to cooling air in the area of a thunderstorm with rain or a dry cold front. After the passage of a dry cold front, convective instability in the troposphere can contribute to the development of a dust storm. In desert regions, dust and sand storms are most often caused by thunderstorm downdrafts and the associated increase in wind speed. The vertical dimensions of a storm are determined by the stability of the atmosphere and the weight of the particles. In some cases, dust and sand storms may be confined to a relatively thin layer due to the temperature inversion effect.
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Ways to fight
To prevent and reduce the effects of dust storms, forest shelterbelts, snow and water retention complexes are created, and also used agrotechnical methods such as grass seeding, crop rotation and contour plowing.
Environmental consequences
Sandstorms can move entire dunes and carry enormous volumes of dust, so that the storm front can appear as a dense wall of dust up to 1.6 km high. Dust and sand storms coming from the Sahara Desert are also known as shamum, khamsin (in Egypt and Israel) and habub (in Sudan).
A large number of dust storms originate in the Sahara, especially in the Bodélé Depression and in the area where the borders of Mauritania, Mali and Algeria converge. Over the past half century (since the 1950s), Saharan dust storms have increased approximately 10-fold, causing a decrease in the thickness of topsoil in Niger, Chad, northern Nigeria and Burkina Faso. In the 1960s, only two dust storms occurred in Mauritania; currently there are 80 storms per year.
Dust from the Sahara is carried westward across the Atlantic Ocean. The intense daytime heating of the desert creates an unstable layer in the lower troposphere, in which spread dust particles. As the air mass moves (advects) westward over the Sahara, it continues to heat up, and then, reaching the oceanic expanses, passes over a colder and more humid atmospheric layer. This temperature inversion prevents the layers from mixing and allows the dusty layer of air to cross the ocean. The amount of dust blown from the Sahara toward the Atlantic Ocean in June 2007 was five times greater than the year before, which could cool Atlantic waters and slightly reduce hurricane activity.
Economic consequences
The main damage caused by dust storms is the destruction of the fertile soil layer, which reduces its agricultural productivity. In addition, the abrasive effect damages young plants. Other possible negative consequences include: reduced visibility affecting air and road transport; reducing the amount of sunlight reaching the Earth's surface; thermal blanket effect; unfavorable impact on the respiratory system of living organisms.
Dust can also be beneficial in places where it is deposited - the jungles of Central and South America receive most of their mineral fertilizers from the Sahara, the lack of iron in the ocean is compensated, dust in Hawaii helps banana crops grow. In northern China and the western United States, ancient storm sediment soils called loess are very fertile, but are also the source of modern dust storms when the vegetation that binds the soil is disrupted.
Extraterrestrial dust storms
The extreme difference in temperature between the ice shell and the warm air at the edge of Mars's southern polar cap results in strong winds that raise huge clouds of red-brown dust. Experts believe that dust on Mars can play the same role as clouds on Earth - it absorbs sunlight and thereby heats the atmosphere.
Known dust and sand storms
Dust storm in Australia (September 2009)
- According to Herodotus, in 525 BC e. died during a sandstorm in the Sahara fifty thousandth army of the Persian king Cambyses.
- In April 1928, in the steppe and forest-steppe regions of Ukraine, the wind lifted more than 15 million tons of chernozem from an area of 1 million km². Black earth dust was transported to the west and settled over an area of 6 million km² in the Carpathian region, Romania and Poland. The height of the dust clouds reached 750 m, the thickness of the black soil layer in the affected regions of Ukraine decreased by 10-15 cm.
- A series of dust storms in the United States and Canada during the Dust Bowl period (1930-1936) forced the move hundreds thousand farmers.
- In second half day 8 February 1983 of the year strongest dusty storm, appeared on north Australian state Victoria, covered city Melbourne.
- IN periods multi-year droughts years 1954 —56 , 1976 —78 And 1987 —91 on territories Northern America arose intensive dusty storms.
- Strong dusty storm 24 February 2007 of the year, appeared on territories western Texas V area cities Amarillo, covered all northern Part state. Strong wind caused numerous damage fences, roofs And even some buildings. Also strongly Suffered international airport metropolis Dallas-Fort—Worth, V hospital contacted People With problems at breathing.
- IN June 2007 of the year big dusty storm happened V Karachi And on territories provinces Sindh And Balochistan, subsequent behind her strong rains brought To of death almost 200 Human .
- 26 May 2008 of the year sandy storm V Mongolia brought To of death 46 Human.
- 23 September 2009 of the year dusty storm V Sydney brought To interruptions V movement transport And forced hundreds Human stay Houses. Over 200 Human contacted behind medical with help from—behind problems With breathing.
- 5 July 2011 of the year huge sandy storm covered
A large number of dust and sand particles. Distributed in deserts, semi-deserts, and arable steppes, where strong winds blow.
1. General description
Dust storms are complex atmospheric phenomena characterized by the transport of dust and sand by strong and prolonged winds that destroy the soil surface. Dust storms, based on the color and composition of the dust that is transferred, are: black (chernozems), brown and yellow (loam, sandy loam), red (loams with an admixture of iron oxides) and white (salt marshes). Very often there are short-term black storms lasting up to one hour, a large number of them can also last from 10 to 12 hours, and relatively rarely such storms last more than a day. Red storms last longer - for several days. The height of dust rising can reach 2-3 km, but most often - 1-1.5 km. In the winter-spring period, snow and dust storms are observed in the central and southern regions of Ukraine
2. Where and when they arise
Dust storms occur in deserts, semi-deserts and steppe regions, where there is soil uncovered by grass. Dust storms can transport millions of tons of dust over hundreds and even thousands of kilometers. The destructive effect of a dust storm occurs additionally through the action of soil particles that move at high speed.
Dust storms usually occur in summer, sometimes in spring or winter when there is no snow. In the steppe zone they also occur due to irrational plowing of the land.
3. Actions in dust storm conditions
A person caught in a dust storm needs to lie down on the leeward side of any tall object that holds firmly to the ground - a stone, a thick bush, etc. The respiratory tract should be protected from sand and dust with a cloth bandage. Place a closed container with a supply of water next to you, under your arm.
4. In Ukraine
In February 1951, strong storms occurred in the Azov region with a speed of 16-18 m/s. They removed the weak snow cover and began to blow away the exposed soil. The snow, together with the blown soil, created many obstacles, forming black snowdrifts up to 1-1.5 meters high. The blowing away of soil and winter crops continued into the spring months.
Dust storms are currently occurring temporarily in southern Ukraine. First of all in
| Origin and types of storms. Their consequences
Basics of life safety
7th grade
Lessons 11 - 13
Hurricanes, storms, tornadoes
Lesson 12
Origin and types of storms. Their consequences
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Hurricane-force winds often lead to storms.
Storm - very strong (with a speed of over 20 m/s) and prolonged wind. Storms are characterized by lower wind speeds than hurricanes, and their duration of action ranges from several hours to several days.
Depending on the time of year, the place of their formation and the entrainment of particles of various compositions into the air, dusty, dustless, snow and squall storms are distinguished.
Storms often occur in areas not covered by forest. A successful way to combat them is to plant forests in steppe and semi-desert areas.
Dust (sand) storms are accompanied by the transfer of large amounts of soil and sand particles. They occur in desert, semi-desert and steppe areas, where there is soil not covered with grass. When there is a strong wind, a large amount of dust and small particles of earth rise into the air. Dust storms can transport millions of tons of dust over hundreds and even thousands of kilometers and cover an area of several hundred thousand square kilometers with it. The destructive impact of such a storm occurs additionally due to the impact of earth particles moving at high speed. Such storms usually occur in the summer, during dry winds, sometimes in the spring and during snowless winters. In the steppe zone they often arise due to irrational plowing of land. In Russia, the northern border of the distribution of dust storms passes through Saratov, Samara, Ufa, Orenburg and the foothills of Altai. For dust-free storms
characterized by the absence of dust entrainment into the air and a relatively smaller scale of destruction and damage. However, as they move, they can turn into dust or snow storms. For snow storms
Significant wind speeds are also characteristic, which contributes to the movement of huge masses of snow through the air in winter. The duration of such storms ranges from several hours to several days. They have a relatively narrow range (from several kilometers to several tens of kilometers). In Russia, snow storms of great force occur on the plains of its European part and in the steppe part of Siberia. For squalls
Characterized by an almost sudden onset, an equally rapid ending, short duration and enormous destructive power. In Russia, these storms are widespread throughout its European part (in marine areas, where they are called squalls, and on land).
Storms are classified depending on the color and composition of the particles involved in the movement, as well as on wind speed (Scheme 13).- these are storms that occur in deserts, semi-deserts and plowed steppes, accompanied by the transfer of large quantities of soil and sand particles. They are capable of transporting millions of tons of dust over hundreds and even thousands of kilometers, covering an area of several hundred thousand square kilometers. Such storms occur mainly in the summer, during dry winds, sometimes in the spring and during snowless winters. In the steppe zone they usually occur due to irrational plowing of land. In Russia, the northern border of the distribution of dust storms passes through Saratov, Samara, Ufa, Orenburg and the foothills of Altai.
Dustless storms- these are storms characterized by the absence of dust entrainment into the air and a relatively smaller scale of destruction and damage. However, with further movement they can turn into a dust or snow storm, depending on the composition and condition of the earth's surface and the presence of snow cover.
Ice storms may occur at the beginning and end of snow storms. They consist of a mixture of rain, snow (grass) and hail.
Grits are small melted grains of ice. These ice grains form in two ways: when raindrops pass through a layer of air with a temperature below freezing, or when snowflakes fall through a layer of air with a temperature above freezing. Unlike hail, which can fall at any time of the year, pellets appear only in winter.
Although graupel is a nuisance, it rarely causes the widespread destruction that hail does. Thus, human and material losses in this section relate entirely to the effects of hailstones.
Hail is precipitation in the form of ice balls and a mixture of ice and snow. Hail typically occurs during the passage of a cold front or during a thunderstorm.
The largest hailstones are simple structures formed when the surface of snowballs melts and freezes again, or becomes covered with water droplets that then freeze. Thus, hailstones have a hard outer shell and a soft core.
Large hailstones with a diameter of 1.2 to 12.5 centimeters are more complex structures.
There are various theories of their formation. They usually consist of alternating layers of hard and soft ice. One theory is that they form in clouds when ultra-cold droplets freeze on dust particles or snowflakes. These tiny hailstones are then repeatedly carried up and down by the wind. Each time they pass through an area with a temperature above freezing, they absorb moisture, and as they rise upward into an area with a temperature below freezing, they either freeze or build up a new layer of snow. Hailstones continually grow until they reach a weight that the wind cannot support, and then they fall to the ground.
Another theory suggests that hailstones pass through various air pockets, building up layers in zones of air containing varying amounts of moisture.
Whatever the method of formation, hail causes amazing destruction and loss of life.
Timeline of the worst ice storms
Snow in its softest form is what children and romantics expect from the first day of November and from the moment the thermometer drops below zero. Snow has the ability to soften the sharp edges of urban landscapes and provides opportunities for boys to play with their imagination.
But in a less mild form, bursting into our lives in the form of a snowstorm, it can become a killer.
Snow itself is precipitation formed by the transition of water vapor into solid crystals at a temperature below freezing. Condensation usually occurs around dust particles in the same way as when raindrops form. Only snowflakes come out in the form of hexagonal plates, among which not a single pair is identical. The differences in size and shape are the result of multiple crystals coming together as snowflakes pass through warmer layers of air.
On average, 250 millimeters of snow equals 25 millimeters of rain, and the factors that determine rainfall are about the same as snowfall.
Blizzards, then, are winter storms characterized by low temperatures, strong winds and snowfall. Whereas a hurricane has tropical temperatures, strong winds and rain. The US Weather Bureau published a collection of definitions in 1958, which indicates the parameters of natural phenomena. So, for northern latitudes, snowfall becomes a blizzard when the wind speed reaches 56 kilometers per hour and the temperature drops below minus seven degrees. Blizzards may extend as far south as Texas and as far east as Maine.
Timeline of the most severe snow storms
Squalls (Squalls)– horizontal vortices under the edge of an advancing band of powerful cumulonimbus clouds. The width of the squall corresponds to the width of the atmospheric front and reaches hundreds of kilometers. The speed of air movement in the vortex adds up to the speed of the front and in some places reaches hurricane speed (up to 60–80 m/s). This is how squalls or storms are formed. Their width is a few kilometers, rarely up to 50 km, the path length is 20–200 km, rarely up to 700 km, the duration at each point of the path is from several to 30 minutes. They are accompanied by heavy downpours and thunderstorms. Squalls and local squall storms are typical for all areas covered by cyclonic activity. Their frequency and seasonality depend on certain characteristics of the colliding air masses and vary from place to place. For the European part of Russia, statistics for the Nizhny Novgorod region are representative: the season of squalls is April - September, maximum frequency (more than 1 day out of 5) - from May 26 to June 10; number of days per season with squalls faster than 15 m/s – 18.1; 20 m/s – 9.3; 25 m/s – 2.4; faster than 30 m/s – 0.8 days.
The destructive impact of squalls is determined by wind speed, as well as thunderstorms and flash floods. In the European part of Russia, one squall can damage crops over an area of up to several tens of thousands of hectares, dozens of houses and outbuildings with one-time damage of up to several million rubles.
Squalls are similar to flow or jet storms. They are associated with atmospheric fronts, but do not have a vertical convective component, as with squalls, and are created by air flows in valleys and along the edges of hills. Storms of this type reach speeds of 40–50 m/s and last 12–24 hours, up to a maximum of a week. These include: Novaya Zemlya, Novorossiysk, Adriatic bora, Orosi in Japan, Sarma and Barguzin on Lake Baikal, Mistral in the Rhone Valley (France), Tramontana in Italy, Chinook from the Rocky Mountains in Canada, Khazri along the eastern edge of the Caucasus near the Caspian Sea and others local storms.
The hazards they cause vary depending on the time of year and local conditions. Let's name some examples: Novorossiysk forest in winter - storm in Tsemes Bay, splashing and icing (ice thickness - up to 4 m) of port buildings; Balkhash forest with ridge. Chingiz - snowstorm in winter, dust storm in summer; hairdryer in the Alps in winter and spring - extreme snowmelt, floods, mudflows, landslides, and if the air temperature is not high enough - severe snowstorms, etc.
Consequences of storms are damage and destruction of buildings, power and communication lines, the formation of drifts and blockages on roads, destruction of agricultural crops, damage and loss of ships. These natural disasters kill animals, injure people, and kill people. People in hurricane and tornado zones are most often struck by flying objects and collapsing structures. A secondary consequence of hurricanes are fires that occur due to accidents on gas communications, power lines, and sometimes as a result of lightning strikes.
Storms lead to much less destructive consequences than hurricanes. However, they, accompanied by the transfer of sand, dust or snow, cause significant damage to agriculture, transport and other sectors of the economy.
Dust storms cover fields, populated areas and roads with a layer of dust (sometimes reaching several tens of centimeters) over areas of hundreds of thousands of square kilometers. In such conditions, the harvest is significantly reduced or completely lost and large amounts of effort and money are required to clean up settlements, roads and restore agricultural land.
Blizzards in our country they often achieve great strength over vast areas. They lead to the cessation of traffic in cities and rural areas, the death of farm animals and even people.
Thus, storms, being dangerous in themselves, in combination with the phenomena accompanying them create a difficult situation, bringing destruction and casualties.
Measures to protect the population from storms:
Timely forecast and warning of the population;
- reducing the impact of secondary damage factors (fires, dam breaks, accidents);
- increasing the stability of communication lines and power supply networks;
- preparation of shelters, basements and other buried structures for sheltering people;
- shelter in durable structures and places that provide protection for farm animals; provision of water and feed for them.
100 great records of the elements [with illustrations] Nepomniachtchi Nikolai Nikolaevich
Worst dust storm ever
Worst dust storm ever
The warriors of the Persian king Cambyses moved forward with difficulty. All around, as far as the eye could see, lay ridges of sand. Having conquered in 525 BC. e. Egypt, the ruler of the Persians did not get along with his priests. The servants of the temple of the god Amun prophesied his imminent death, and Cambyses decided to punish them. An army of fifty thousand was sent on the campaign. Her path ran through the Libyan desert. Seven days later, the Persians reached the large oasis of Kharga, and then... disappeared without a trace.
Talking about this, the ancient Greek historian Herodotus adds: “Apparently, the warriors of Cambyses were destroyed by a strong sandstorm.”
There are many descriptions of sandstorms in deserts. Nowadays, when the desert is crossed by highways, and air routes run above them in all directions, travelers are no longer in danger of dying on the great caravan routes. But first...
An hour or half an hour before a merciless storm arises, the bright sun dims and becomes covered in a cloudy veil. A small dark cloud appears on the horizon. It quickly increases, covering the blue sky. Here came the first fierce gust of hot, prickly wind. And within a minute the day fades. Clouds of burning sand mercilessly cut all living things, covering the midday sun. All other sounds disappear in the howling and whistling of the wind. “Both people and animals were suffocating. What was missing was the air itself, which seemed to rise upward and fly away along with the reddish, brown haze that had already completely covered the horizon. My heart was pounding terribly, my head ached mercilessly, my mouth and throat were dry, and it seemed to me that another hour and death by suffocation by sand was inevitable.” So the Russian traveler of the 19th century A.V. Eliseev describes a storm in the deserts of North Africa.
Sandstorms - simooms - have long been covered with gloomy fame. It’s not for nothing that they have this name: samum means “poisonous”, “poisoned”. Samums actually destroyed entire caravans. So, in 1805, the simoom, according to the testimony of many authors, covered two thousand people and one thousand eight hundred camels with sand. And, quite possibly, the same storm once destroyed the army of Cambyses.
It happens that the testimonies of people who survived the test of the elements are guilty of exaggeration. However, there is no doubt: samum is very dangerous.
Fine sand dust, which is raised by a strong wind, penetrates the ears, eyes, nasopharynx, and lungs. Streams of dry air inflame the skin and cause excruciating thirst. To save their lives, people lie down on the ground and cover their heads tightly with clothes. It happens that from suffocation and high temperature, often reaching fifty degrees, they lose consciousness. Here is an excerpt from the travel notes of the Hungarian explorer of Central Asia A. Vambery: “In the morning we stopped at a station with the cute name Adamkirilgan (place of death), and we only had to look around to see that this name was not given for nothing. Imagine a sea of sand, going in all directions as far as the eye can see, torn by the winds and representing, on the one hand, a series of high hills lying in ridges, like waves, and on the other, like the surface of a lake, smooth and covered with wrinkles of ripples. Not a single bird in the air, not a single animal on the ground, not even a worm or grasshopper. There were no signs of life, except for bones, whitened in the sun, collected by each passer-by and placed in the path to make it easier to walk... Despite the oppressive heat, we were forced to walk day and night, for five to six hours at a time. We had to hurry: the sooner we get out of the sands, the less danger there is of falling under the tebbad (feverish wind), which could cover us with sand if it catches us on the dunes... When we approached the hills, the caravan bashis and guides pointed out to us the approaching cloud of dust , warning that you need to dismount. Our poor camels, more experienced than we ourselves, already felt the approach of the Tebbad, roared desperately and fell to their knees, stretching their heads along the ground, and tried to bury them in the sand. We hid behind them, as if behind cover. The wind came with a dull noise and soon covered us with a layer of sand. The first grains of sand that touched my skin gave the impression of fiery rain..."
This unpleasant meeting took place between Bukhara and Khiva. Many desert storms owe their birth to passing cyclones that also affect deserts. There is another reason: in deserts during the hot season, atmospheric pressure decreases. Hot sands greatly heat the air at the surface of the earth. As a result, it rises, and in its place flows of colder dense air rush at very high speeds. Small local cyclones form, giving rise to sandstorms.
Very peculiar air currents, reaching great strength, are observed in the Pamir Mountains. Their reason is the extremely sharp difference between the temperature of the earth's surface, strongly heated by the bright mountain sun, and the temperature of the upper, very cold layers of air. The winds here reach particular intensity in the middle of the day, and often turn into hurricanes, raising sandstorms. And in the evening they usually subside. In some areas of the Pamirs the winds are so strong that caravans still sometimes die there. One of the valleys here is called the Valley of Death; it is strewn with the bones of dead animals...
The same winds often occur in the Balkhan corridor in Turkmenistan. Situated between the Kopet Dag Range and the Great Balkhan Mountains, this corridor stretches towards the Caspian Sea. In the spring, when the atmospheric pressure over the desert decreases, masses of not yet warmed-up heavy air rush here from the Caspian Sea. Bursting into the Balkhan corridor, squeezed by mountains, the air flow acquires the speed of a storm. In autumn, the opposite picture is observed here: the waters of the Caspian Sea retain the heat accumulated in the summer for a long time, and air flows from the desert, where the sands have long cooled, rush towards it.
Our Far East is also familiar with such storms: “...A sandstorm is mercilessly and inexorably approaching from the vastness of Mongolia,” wrote Khabarovsk geographer G. Permyakov. – The brown haze is clouding the sky thicker and thicker. The sun turns crimson red. There is an oppressive warm silence in the air. It’s getting harder to breathe, my lips are getting dry. It gets dark quickly, it seems that the bloody sun is fading. Warm dust mixed with sand is rushing from the west... A sand hurricane in the city. It breaks trees and poles like matches, and tears off the roofs of houses and barns with a clanging sound. Everything is captivated by the pervasive sandy dust and the warm, drying wind. The trams stopped. The cars have disappeared. Soon, deep night seems to fall on the city... Sirens howl sadly, warning: “Danger! Stop the movement!..”
Samum is born in Xinjiang, on the huge Mongolian rocky plateau. The storm dust is so light that a strong wind lifts it to a height of five to seven kilometers and carries it through Dzungaria, the Mongolian Plateau, the northeast and north of China to the ocean.
Over the Korean Peninsula and the Soviet Far East, the samum is already noticeably weakening, lowering its brown, dusty wings. If the African-Arabian samum usually lasts 15–20 minutes and strikes with a monstrous squall forty times a year, then the Mongolian howls sometimes for several days and in the east of our country rarely happens more than two or three times a year. Its weakened waves reach Khabarovsk, Ussuriysk, Vladivostok, Komsomolsk and even the Sea of Japan. Then the bright Khabarovsk sky turns yellow, as if it had been covered with a canary veil. A smoky red sun shines through the haze. A light ocher coating settles on the ground... The dust storm leaves majestically and gradually. First, the sky turns from burnt chocolate to coffee, then ashy; then it turns gray, and the dark disk of the sun appears through the cloudy curtain of running clouds. The hours pass, the samum dies down. The sun turns burgundy, then red, dark orange and finally takes on all the splendor of its dazzling brilliance. It's getting chilly. Dirty rain begins... Sand whirlwinds are very dangerous in the deserts of Asia and Africa. They sometimes reach enormous sizes. Hot sand heats the air to 50 degrees or more. The air rushes upward with force. If, for some reason, neighboring areas are heated to a lesser extent, then vortices will form here. Rising upward in a spiral, the vortex carries masses of sand with it. A rotating pillar of sand forms above the ground. Sweeping away everything, it rushes forward, increasing in size. It happens that one such whirlwind is followed by several others. They circle around the desert for many hours, collide, crumble, and are born again.”
The North American arid steppes are also familiar with menacing dust devils. This is how Mine Reed described them in the novel “The Headless Horseman”: “Several completely black columns suddenly appeared over the prairie on the north side - there were about ten of them... These huge pillars either stood motionless, or glided along the charred ground, like giants on skates, bending and leaning towards each other, as if in the fantastic figures of some strange dance. Imagine the legendary titans who came to life on the Texas prairie and danced in a frantic orgy.”
Dust storms with tornadoes often occur in the deserts of Africa, Central and Central Asia. The most famous and detailed dust devil was the Red Dust Storm of 1901.
It began in the north of the Sahara on March 9 and by the morning of the next day had spread to the entire coast of Tunisia and Tripolitania. The air, filled with reddish dust, was impenetrable; the sun was not visible, darkness fell. Panic began among the population. By one o'clock in the afternoon the storm had reached its maximum, and everything was covered with a layer of dust of dark yellow and pink colors.
While the main cloud was moving over Tunisia, its borders had already crossed the Mediterranean Sea and reached Sicily.
By evening, the dust storm, still at the speed of a hurricane, reached northern Italy, and at night it spread to the entire Eastern Alps, covering the snow and glaciers with a dense layer of red dust. In some places there was “bloody rain” here too, but with less intensity. By the morning of March 11, the storm crossed the Alps and moved north. By mid-afternoon it had spread to northern Germany and, quickly fading, reached Denmark, the Baltic Sea and Russia. The total weight of dust falling during the storm in Europe is approximately 1.8 million tons.
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Essay
on the topic : Tsunami and dust (sand) storm.
Performed:student
group RMM-07
Nurgalieva N.R.
Checked: Kondyurin V.G.
Moscow 2010
Tsunami
Tsunami- these are long waves generated by a powerful impact on the entire thickness of water in the ocean or other body of water. Most tsunamis are caused by underwater earthquakes, during which a sharp displacement (raising or lowering) of a section of the seabed occurs. Tsunamis are formed during an earthquake of any strength, but those that arise due to strong earthquakes (more than 7 points) reach great strength. As a result of an earthquake, several waves are propagated. More than 80% of tsunamis occur on the periphery of the Pacific Ocean. The first scientific description of the phenomenon was given by José de Acosta in 1586 in Lima, Peru, after a powerful earthquake, then a tsunami 25 meters high burst onto land at a distance of 10 km.
In the open ocean, tsunami waves propagate at a speed where g is the gravitational acceleration and H is the depth of the ocean (the so-called shallow water approximation, when the wavelength is significantly greater than the depth). With an average depth of 4000 meters, the propagation speed is 200 m/s or 720 km/h. In the open ocean, the wave height rarely exceeds one meter, and the wave length (the distance between crests) reaches hundreds of kilometers, and therefore the wave is not dangerous for shipping. When waves enter shallow water, near the coastline, their speed and length decrease, and their height increases. Near the coast, the height of a tsunami can reach several tens of meters. The highest waves, up to 30-40 meters, form along steep shores, in wedge-shaped bays and in all places where focusing can occur. Coastal areas with closed bays are less dangerous. A tsunami usually appears as a series of waves; since the waves are long, more than an hour can pass between wave arrivals. That is why you should not return to the shore after the next wave leaves, but wait a few hours.
Causes of tsunami formation
Underwater earthquake(about 85% of all tsunamis). During an earthquake under water, a vertical movement of the bottom is formed: part of the bottom sinks, and part rises. The surface of the water begins to oscillate vertically, trying to return to its original level - the average sea level - and generates a series of waves. Not every underwater earthquake is accompanied by a tsunami. Tsunamigenic (that is, generating a tsunami wave) is usually an earthquake with a shallow source. The problem of recognizing the tsunamigenicity of an earthquake has not yet been solved, and warning services are guided by the magnitude of the earthquake. The most powerful tsunamis are generated in subduction zones.
Landslides. Tsunamis of this type occur more frequently than estimated in the 20th century (about 7% of all tsunamis). Often an earthquake causes a landslide and it also generates a wave. On July 9, 1958, an earthquake in Alaska caused a landslide in Lituya Bay. A mass of ice and earth rocks collapsed from a height of 1100 m. A wave was formed that reached a height of more than 500 m on the opposite shore of the bay. Cases of this kind are very rare and, of course, are not considered as a standard. But underwater landslides occur much more often in river deltas, which are no less dangerous. An earthquake can cause a landslide and, for example, in Indonesia, where shelf sedimentation is very large, landslide tsunamis are especially dangerous, as they occur regularly, causing local waves more than 20 meters high.
Volcanic eruptions(about 4.99% of all tsunamis). Large underwater eruptions have the same effect as earthquakes. With strong volcanic explosions, not only are waves generated from the explosion, but water also fills the cavities of the erupted material or even the caldera, resulting in a long wave. A classic example is the tsunami generated after the Krakatoa eruption in 1883. Huge tsunamis from the Krakatoa volcano were observed in harbors around the world and destroyed a total of 5,000 ships and killed 36,000 people.
Other Possible Causes
Human activity. In our age of atomic energy, man has in his hands a means of causing shocks that were previously only available to nature. In 1946, the United States carried out an underwater atomic explosion with a TNT equivalent of 20 thousand tons in a sea lagoon 60 m deep. The wave that arose at a distance of 300 m from the explosion rose to a height of 28.6 m, and 6.5 km from the epicenter still reached 1.8 m. But for long-distance propagation of the wave, it is necessary to displace or absorb a certain volume of water, and a tsunami from underwater landslides and explosions are always local in nature. If several hydrogen bombs are simultaneously detonated on the ocean floor, along any line, then there will be no theoretical obstacles to the occurrence of a tsunami; such experiments have been carried out, but have not led to any significant results compared to more accessible types of weapons. Currently, any underwater testing of atomic weapons is prohibited by a series of international treaties.
The fall of a large celestial body can cause a huge tsunami, since, having a huge falling speed, these bodies also have colossal kinetic energy, which will be transferred to the water, resulting in a wave. Thus, the fall of a meteorite 65 million years ago also caused a tsunami, the deposits of which were found in the state of Texas.
Wind can cause large waves (up to about 20 m), but such waves are not tsunamis, since they are short-period and cannot cause flooding on the coast. However, the formation of a meteo-tsunami is possible with a sharp change in pressure or with a rapid movement of an atmospheric pressure anomaly. This phenomenon is observed in the Balearic Islands and is called Rissaga.
Signs of a tsunami
A sudden rapid withdrawal of water from the shore over a considerable distance and drying out of the bottom. The further the sea recedes, the higher the tsunami waves can be. People on the shore who are unaware of the danger may remain out of curiosity or to collect fish and shells. This rule should be followed when, for example, in Japan, on the Indian Ocean coast of Indonesia, or Kamchatka. In the case of a teletsunami, the wave usually approaches without the water receding.
Earthquake. The epicenter of an earthquake is usually in the ocean. On the coast, the earthquake is usually much weaker, and often there is no earthquake at all. In tsunami-prone regions, there is a rule that if an earthquake is felt, it is better to move further from the coast and at the same time climb a hill, thus preparing in advance for the arrival of the wave.
Unusual drift of ice and other floating objects, formation of cracks in fast ice.
Huge reverse faults at the edges of stationary ice and reefs, the formation of crowds and currents
Why does a tsunami often cause large casualties?
It may not be clear why a tsunami several meters high turned out to be catastrophic, while waves of the same height that arose during a storm did not lead to casualties or destruction? There are several factors that lead to catastrophic consequences:
- The height of the wave near the coast in the event of a tsunami, generally speaking, is not a determining factor. Depending on the configuration of the bottom near the coast, the tsunami phenomenon can occur without a wave at all, in the usual sense, but as a series of rapid ebbs and flows, which can also lead to casualties and destruction.
- During a storm, only the surface layer of water begins to move; during a tsunami, the entire thickness moves. And during a tsunami, much larger masses of water splash onto the shore.
- The speed of tsunami waves, even near the shore, exceeds the speed of wind waves. Tsunami waves have more kinetic energy.
- A tsunami, as a rule, generates not one, but several waves. The first wave, not necessarily the largest, wets the surface, reducing resistance for subsequent waves.
- During a storm, excitement increases gradually; people usually manage to move to a safe distance before large waves arrive. The tsunami comes suddenly.
- The strength of a tsunami can increase in the harbor - where wind waves are weakened, and therefore residential buildings can be located close to the shore.
- Lack of basic knowledge among the population about possible dangers. Thus, during the 2004 tsunami, when the sea retreated from the coast, many local residents remained on the shore - out of curiosity or out of a desire to collect fish that had not managed to escape. In addition, after the first wave, many returned to their homes to assess the damage or try to find loved ones, unaware of subsequent waves.
- The tsunami warning system is not available everywhere and does not always work.
- The destruction of coastal infrastructure aggravates the disaster, adding catastrophic man-made and social factors. Flooding of lowlands and river valleys leads to soil salinization.
Tsunami warning systems
Tsunami warning systems are based mainly on the processing of seismic information. If an earthquake has a magnitude greater than 7.0 (in the press this is called the Richter scale) and the epicenter is located under water, then a tsunami warning is issued. Depending on the region and the population of the shores, the conditions for generating an alarm signal may be different.
The second possibility of warning about a tsunami is a warning “after the fact” - a more reliable method, since there are practically no false alarms, but often such a warning can be generated too late. The warning after the fact is useful for teletsunamis - global tsunamis that affect the entire ocean and arrive at other ocean boundaries a few hours later. Thus, the Indonesian tsunami in December 2004 is a teletsunami for Africa. A classic case is the Aleutian tsunami - after a strong splash in the Aleutians, you can expect a significant splash in the Hawaiian Islands. Bottom hydrostatic pressure sensors are used to detect tsunami waves in the open ocean. A warning system based on such sensors with satellite communication from a near-surface buoy, developed in the United States, is called DART (en:Deep-ocean Assessment and Reporting of Tsunamis). Having detected a real wave in one way or another, it is possible to quite accurately determine the time of its arrival in various populated areas.
An essential aspect of the warning system is the dissemination of up-to-date information among the population. It is very important that the population understands the threat a tsunami poses. The Japanese have many educational programs on natural disasters, and in Indonesia the population was largely unfamiliar with tsunamis, which was the main reason for the large number of casualties. The legislative framework for the development of the coastal zone is also important.
The largest tsunamis
November 5, 1952 Severo-Kurilsk (USSR).
Caused by a powerful earthquake (magnitude estimates from various sources range from 8.3 to 9), which occurred in the Pacific Ocean 130 kilometers from the coast of Kamchatka. Three waves up to 15-18 meters high (according to various sources) destroyed the city of Severo-Kurilsk and caused damage to a number of other settlements. According to official data, more than two thousand people died.
03/09/1957 Alaska, (USA).
Caused by a magnitude 9.1 earthquake that occurred in the Andrean Islands (Alaska), which caused two waves, with average wave heights of 15 and 8 meters, respectively. In addition, as a result of the earthquake, the Vsevidov volcano, located on the island of Umnak and which had not erupted for about 200 years, woke up. More than 300 people died in the disaster.
07/09/1958 . Lituya Bay, (southwest Alaska, USA).
An earthquake that occurred north of the bay (on the Fairweather Fault) initiated a strong landslide on the slope of the mountain located above Lituya Bay (about 300 million cubic meters of earth, rocks and ice). All this mass overwhelmed the northern part of the bay and caused a huge wave 524 meters high, moving at a speed of 160 km/h.
03/28/1964 Alaska, (USA).
The largest earthquake in Alaska (magnitude 9.2), which occurred in Prince William Sound, caused a tsunami of several waves, with the highest height being 67 meters. As a result of the disaster (mainly due to the tsunami), according to various estimates, from 120 to 150 people died.
07/17/1998 Papua New Guinea
A magnitude 7.1 earthquake off the northwestern coast of New Guinea triggered a massive underwater landslide that generated a tsunami that killed more than 2,000 people.
XXI Century
06.09.2004 coast of japan
110 km from the coast of the Kii Peninsula and 130 km from the coast of Kochi Prefecture, two strong earthquakes occurred (magnitudes up to 6.8 and 7.3, respectively), causing a tsunami with wave heights of up to one meter. Several dozen people were injured.
26.12.2004 Southeast Asia.
At 00:58, a powerful earthquake occurred - the second most powerful of all recorded (magnitude 9.3), which caused the most powerful tsunami of all known. The tsunami affected Asian countries (Indonesia - 180 thousand people, Sri Lanka - 31-39 thousand people, Thailand - more than 5 thousand people, etc.) and African Somalia. The total number of deaths exceeded 235 thousand people.
01/09/2005 . Izu and Miyake Islands (eastern Japan)
An earthquake of magnitude 6.8 caused a tsunami with a wave height of 30-50 cm. However, thanks to timely warning, the population was evacuated from dangerous areas.
2.04.2007 .Solomon Islands (archipelago)
Caused by a magnitude 8 earthquake that occurred in the South Pacific. Waves several meters high reached New Guinea. The tsunami killed 52 people.
Dust (sand) storm
Dust (sand) storm is an atmospheric phenomenon in the form of the transfer of large quantities of dust (soil particles, grains of sand) by wind from the earth's surface in a layer several meters high with a noticeable deterioration in horizontal visibility (usually at a level of 2 m it ranges from 1 to 9 km, but in in some cases it can drop to several hundred and even several tens of meters). In this case, dust (sand) rises into the air and, at the same time, dust settles over a large area. Depending on the color of the soil in a given region, distant objects take on a grayish, yellowish or reddish tint. It usually occurs when the soil surface is dry and the wind speed is 10 m/s or more.
Often occurs during the warm season in desert and semi-desert regions. In addition to the “actual” dust storm, in some cases dust from deserts and semi-deserts can remain in the atmosphere for a long time and reach almost anywhere in the world in the form of a dusty haze.
Dust storms occur less frequently in steppe regions, very rarely in forest-steppe and even forest regions (in the last two zones, a dust storm usually occurs in the summer during severe drought). In the temperate zone, dust storms usually occur in early spring, after a winter with little snow and a dry autumn, but sometimes they occur even in winter, in combination with blizzards.
When a certain threshold of wind speed is exceeded (depending on the mechanical composition of the soil and its moisture), particles of dust and sand come off the surface and are transported by saltation and suspension, causing soil erosion.
Dusty (sandy) drifting snow - the transfer of dust (soil particles, grains of sand) by wind from the earth's surface in a layer 0.5-2 m high, which does not lead to a noticeable deterioration in visibility (if there are no other atmospheric phenomena, horizontal visibility at a level of 2 m is 10 km or more ). It usually occurs when the soil surface is dry and the wind speed is 6-9 m/s or more.
Geography
The main distribution area of dust storms is deserts and semi-deserts of the temperate and tropical climatic zones of both hemispheres of the Earth.
The term dust storm is usually used when a storm occurs over clay and loam soil. When storms occur in sandy deserts (especially in the Sahara, but also in the Karakum, Kyzylkum, etc.), when in addition to small particles that reduce visibility, the wind also carries millions of tons of larger sand particles over the surface, the term sandstorm is used.
A high frequency of dust storms is observed in the Aral and Balkhash regions (southern Kazakhstan), on the coasts of the Caspian Sea, in the West Kazakhstan region, in Karakalpakstan and Turkmenistan. In Russia, dust storms are most often observed in the Astrakhan region, in the east of the Volgograd region and in Kalmykia.
During long periods of dry weather, dust storms can develop (not annually) in the steppe and forest-steppe zones: in Russia - in the Chita region, Buryatia, Tuva, Altai Territory, Omsk, Kurgan, Chelyabinsk, Orenburg regions, Bashkiria, Samara, Saratov, Voronezh, Rostov regions, Krasnodar and Stavropol territories; in Ukraine - in Lugansk, Donetsk, Nikolaev, Odessa, Kherson regions, in Crimea; in northern, central and eastern Kazakhstan.
During a squall (before a thunderstorm and torrential rain), short-term (from several minutes to an hour) local dust storms can be observed in the summer even at points located in the forest vegetation zone - including in Moscow and St. Petersburg (1-3 days per summer).
The Sahara Desert and deserts of the Arabian Peninsula are the main sources of dust haze in the Arabian Sea region, with smaller contributions from Iran, Pakistan and India. Dust storms in China carry dust into the Pacific Ocean. Environmentalists believe that irresponsible management of the Earth's arid regions, such as ignoring crop rotation, is leading to an increase in desert areas and climate change at the local and global levels.
Causes
Dust Bowl in the United States that began in 1935.
With an increase in the strength of the wind flow passing over loose particles, the latter begin to vibrate and then “jump”. When these particles repeatedly strike the ground, they create fine dust that rises in suspension.
A recent study suggests that the initial saltation of sand grains by friction induces an electrostatic field. The bouncing particles acquire a negative charge, which releases even more particles. This process captures twice as many particles as previous theories predict.
Particles are released mainly due to dry soil and increased wind. Gust fronts can occur due to cooling air in the area of a rain storm or dry cold front. After the passage of a dry cold front, convective instability in the troposphere can contribute to the development of a dust storm. In desert regions, dust and sand storms most often occur as a result of thunderstorm downdrafts and the associated increase in wind speed. The vertical dimensions of a storm are determined by the stability of the atmosphere and the weight of the particles. In some cases, dust and sand storms may be confined to a relatively thin layer due to the temperature inversion effect.
Ways to fight
To prevent and reduce the effects of dust storms, forest shelterbelts, snow and water retention complexes are created, and agricultural methods such as grass sowing, crop rotation and contour plowing are used.
Environmental consequences
Sandstorms can move entire dunes and carry enormous volumes of dust, so that the front of the storm can appear as a dense wall of dust up to 1.6 km high. Dust and sand storms coming from the Sahara Desert are also known as shamum, khamsin (in Egypt and Israel) and habub (in Sudan).
A large number of dust storms originate in the Sahara, especially in the Bodélé Depression and in the area where the borders of Mauritania, Mali and Algeria converge. Over the past half century (since the 1950s), Saharan dust storms have increased approximately 10-fold, causing a decrease in the thickness of topsoil in Niger, Chad, northern Nigeria and Burkina Faso. In the 1960s, Mauritania experienced only two dust storms, but currently experiences 80 storms per year.
Dust from the Sahara is carried westward across the Atlantic Ocean. The intense daytime heating of the desert creates an unstable layer in the lower troposphere in which dust particles spread. As the air mass moves (advects) westward over the Sahara, it continues to heat up, and then, reaching the oceanic expanses, passes over a colder and wetter atmospheric layer. This temperature inversion prevents the layers from mixing and allows the dusty layer of air to cross the ocean. The amount of dust blown from the Sahara towards the Atlantic Ocean in June 2007 was five times greater than the year before, which could cool the Atlantic waters and slightly reduce hurricane activity.
Economic consequences
The main damage caused by dust storms is the destruction of the fertile soil layer, which reduces its agricultural productivity. In addition, the abrasive effect damages young plants. Other possible negative impacts include: reduced visibility affecting air and road transport; reducing the amount of sunlight reaching the Earth's surface; thermal blanket effect; adverse effects on the respiratory system of living organisms.
Dust can also be beneficial in places where it is deposited - the jungles of Central and South America receive most of their mineral fertilizers from the Sahara, the lack of iron in the ocean is replenished, dust in Hawaii helps banana crops grow. In northern China and the western United States, ancient storm sediment soils called loess are very fertile, but are also the source of modern dust storms when the vegetation that binds the soil is disrupted.
Extraterrestrial dust storms.
The extreme difference in temperature between the ice shell and the warm air at the edge of Mars' southern polar cap results in strong winds that kick up huge clouds of red-brown dust. Experts believe that dust on Mars can play the same role as clouds on Earth - it absorbs sunlight and thereby heats the atmosphere.
Known dust and sand storms
Dust storm in Australia (September 2009)
According to Herodotus, in 525 BC. e. During a sandstorm in the Sahara, fifty thousand troops of the Persian king Cambyses died.
In April 1928, in the steppe and forest-steppe regions of Ukraine, the wind lifted more than 15 million tons of chernozem from an area of 1 million km². Black earth dust was transported to the west and settled over an area of 6 million km² in the Carpathian region, Romania and Poland. The height of the dust clouds reached 750 m, the thickness of the black soil layer in the affected regions of Ukraine decreased by 10-15 cm.
A series of dust storms across the United States and Canada during the Dust Bowl period (1930-1936) forced hundreds of thousands of farmers to relocate.
On the afternoon of February 8, 1983, a severe dust storm that appeared in the north of the Australian state of Victoria covered the city of Melbourne.
During periods of multi-year droughts in 1954-56, 1976-78 and 1987-91, intense dust storms occurred in North America.
A severe dust storm on February 24, 2007, which appeared in West Texas near the city of Amarillo, covered the entire northern part of the state. Strong winds caused widespread damage to fences, roofs and even some buildings. The Dallas-Fort Worth International Airport was also heavily damaged, and people were sent to the hospital with breathing problems.
In June 2007, a large dust storm occurred in Karachi and the provinces of Sindh and Balochistan, and the subsequent heavy rains resulted in the death of almost 200 people.
On 23 September 2009, a dust storm in Sydney caused traffic disruptions and forced hundreds of people to stay home. More than 200 people sought medical help due to breathing problems.