In geography, a plain is a flat, sweeping landmass that does not change much in elevation. Plains occur as lowlands along the bottoms of valleys or on the doorsteps of mountains, as coastal plains, as plateaus or uplands. In a valley, a plain is enclosed on two sides, but in other cases a plain may be delineated by a complete or partial ring of hills, by mountains, or by cliffs. Where a geological region contains more than one plain, they may be connected by a pass. Coastal plains would rise from sea level until they run into elevated features such as mountains or plateaus. Plains are one of the major landforms on earth, where they are present on all continents, would cover more than one-third of the world’s land area. Plains may have been formed from flowing lava, deposited by water, wind, or formed by erosion by these agents from hills and mountains. Plains would be under the grassland, savannah or tundra biomes. In a few instances and rainforests can be plains. Plains in many areas are important for agriculture because where the soils were deposited as sediments they may be deep and fertile, the flatness facilitates mechanization of crop production.
Depositional plains formed by the deposition of materials brought by various agents of transportation such as glaciers, rivers and wind. Their fertility and economic relevance depend on the types of sediments that are laid down; the types of depositional plains include: Abyssal plains, flat or gently sloping areas of the deep ocean basin. Planitia, the Latin word for plain, is used in the naming of plains on extraterrestrial objects, such as Hellas Planitia on Mars or Sedna Planitia on Venus. Alluvial plains, which are formed by rivers and which may be one of these overlapping types: Alluvial plains, formed over a long period of time by a river depositing sediment on their flood plains or beds, which become alluvial soil; the difference between a flood plain and an alluvial plain is: a flood plain represents areas experiencing flooding regularly in the present or whereas an alluvial plain includes areas where a flood plain is now and used to be, or areas which only experience flooding a few times a century.
Flood plain, adjacent to a lake, stream, or wetland that experiences occasional or periodic flooding. Scroll plain, a plain through which a river meanders with a low gradient. Glacial plains, formed by the movement of glaciers under the force of gravity: Outwash plain, a glacial out-wash plain formed of sediments deposited by melt-water at the terminus of a glacier. Sandar consist of stratified gravel and sand. Till plains, plain of glacial till that form when a sheet of ice becomes detached from the main body of a glacier and melts in place depositing the sediments it carries. Till plains are composed of unsorted material of all sizes. Lacustrine plains, plains that formed in a lacustrine environment, that is, as the bed of a lake. Lava plains, formed by sheets of flowing lava. Erosional plains have been leveled by various agents of denudation such as running water, rivers and glacier which wear out the rugged surface and smoothens them. Plain resulting from the action of these agents of denudation are called peneplains while plains formed from wind action are called pediplains.
Structural plains are undisturbed horizontal surfaces of the Earth. They are structurally depressed areas of the world that make up some of the most extensive natural lowlands on the Earth's surface. Altiplano Altiplano Cundiboyacense Caroni Plain Chilean Central Valley Gran Chaco Los Llanos Venezuelan Llanos Argentine Pampas Atlantic coastal plain Carrizo Plain Great Plains Gulf Coastal Plain Interior Plains Lake Superior Lowland Laramie Plains Mississippi Alluvial Plain Oxnard Plain Snake River Plain Chianan Plain Depsang Plains Kantō Plain Kedu Plain Kewu Plain Mallig Plains Nōbi Plain North China Plain Osaka Plain Pingtung Plain Sarobetsu plain West Siberian Plain Yilan Plain Bhuikhel Depsang Plains Dooars Eastern coastal plains Indo-Gangetic Plains More plains North Bengal plains Punjab Plains Terai Utkal Plains Western coastal plains Al-Ghab Plain Aleppo plateau Ararat plain Israeli coastal plain Khuzestan Plain Mugan plain Nineveh Plains Shiraki Plain Limagne North German Plain Ochsenfeld Pannonian Basin Parndorf Plain Westphalian Lowland Bărăgan Plain Danubian Plain Dnieper Lowland East European Plain European Plain Great Hungarian Plain Kosovo field Little Hungarian Plain Pannonian Steppe Polesian Lowland Upper Thracian Plain Wallachian Plain Cheshire Plain Hardangervidda Kaffiøyra Muddus plains North
A bean is a seed of one of several genera of the flowering plant family Fabaceae, which are used for human or animal food. The word "bean" and its Germanic cognates have existed in common use in West Germanic languages since before the 12th century, referring to broad beans and other pod-borne seeds; this was long. After Columbian-era contact between Europe and the Americas, use of the word was extended to pod-borne seeds of Phaseolus, such as the common bean and the runner bean, the related genus Vigna; the term has long been applied to many other seeds of similar form, such as Old World soybeans, chickpeas, other vetches, lupins, to those with slighter resemblances, such as coffee beans, vanilla beans, castor beans, cocoa beans. Thus the term "bean" in general usage can mean a host of different species. Seeds called "beans" are included among the crops called "pulses", although a narrower prescribed sense of "pulses" reserves the word for leguminous crops harvested for their dry grain; the term bean excludes legumes with tiny seeds and which are used for forage and silage purposes.
According to the United Nations Food and Agriculture Organization the term "BEANS, DRY" should include only species of Phaseolus. One is that in the past, several species, including Vigna angularis, mungo and aconitifolia, were classified as Phaseolus and reclassified. Another is that it is not surprising that the prescription on limiting the use of the word, because it tries to replace the word's older senses with a newer one, has never been followed in general usage. Unlike the related pea, beans are a summer crop that need warm temperatures to grow. Maturity is 55–60 days from planting to harvest; as the bean pods mature, they turn yellow and dry up, the beans inside change from green to their mature colour. As a vine, bean plants need external support, which may be provided in the form of special "bean cages" or poles. Native Americans customarily grew them along with corn and squash, with the tall cornstalks acting as support for the beans. In more recent times, the so-called "bush bean" has been developed which does not require support and has all its pods develop simultaneously.
This makes the bush bean more practical for commercial production. Beans are one of the longest-cultivated plants. Broad beans called fava beans, in their wild state the size of a small fingernail, were gathered in Afghanistan and the Himalayan foothills. In a form improved from occurring types, they were grown in Thailand since the early seventh millennium BCE, predating ceramics, they were deposited with the dead in ancient Egypt. Not until the second millennium BCE did cultivated, large-seeded broad beans appear in the Aegean and transalpine Europe. In the Iliad is a passing mention of beans and chickpeas cast on the threshing floor. Beans were an important source of protein throughout Old and New World history, still are today; the oldest-known domesticated beans in the Americas were found in Guitarrero Cave, an archaeological site in Peru, dated to around the second millennium BCE. However, genetic analyses of the common bean Phaseolus shows that it originated in Mesoamerica, subsequently spread southward, along with maize and squash, traditional companion crops.
Most of the kinds eaten fresh or dried, those of the genus Phaseolus, come from the Americas, being first seen by a European when Christopher Columbus, during his exploration of what may have been the Bahamas, found them growing in fields. Five kinds of Phaseolus beans were domesticated by pre-Columbian peoples: common beans grown from Chile to the northern part of what is now the United States, lima and sieva beans, as well as the less distributed teparies, scarlet runner beans and polyanthus beans One famous use of beans by pre-Columbian people as far north as the Atlantic seaboard is the "Three Sisters" method of companion plant cultivation: In the New World, many tribes would grow beans together with maize, squash; the corn would not be planted in rows as is done by European agriculture, but in a checkerboard/hex fashion across a field, in separate patches of one to six stalks each. Beans would be planted around the base of the developing stalks, would vine their way up as the stalks grew.
All American beans at that time were vine plants, "bush beans" having been bred only more recently. The cornstalks would work as a trellis for the beans, the beans would provide much-needed nitrogen for the corn. Squash would be planted in the spaces between the patches of corn in the field, they would be provided slight shelter from the sun by the corn, would shade the soil and reduce evaporation, would deter many animals from attacking the corn and beans because their coarse, hairy vines and broad, stiff leaves are difficult or uncomfortable for animals such as deer and raccoons to walk through, crows to land on, etc. Dry beans come from both Old World varieties of New World varieties. Beans are a heliotropic plant. At night, they go into a folded "sleep" position; the world genebanks hold about 40,000 bean varieties, although on
Irrigation is the application of controlled amounts of water to plants at needed intervals. Irrigation helps to grow agricultural crops, maintain landscapes, revegetate disturbed soils in dry areas and during periods of less than average rainfall. Irrigation has other uses in crop production, including frost protection, suppressing weed growth in grain fields and preventing soil consolidation. In contrast, agriculture that relies only on direct rainfall is referred to as rain-fed or dry land farming. Irrigation systems are used for cooling livestock, dust suppression, disposal of sewage, in mining. Irrigation is studied together with drainage, the removal of surface and sub-surface water from a given area. Irrigation has been a central feature of agriculture for over 5,000 years and is the product of many cultures, it was the basis for economies and societies across the globe, from Asia to the Southwestern United States. Archaeological investigation has found evidence of irrigation in areas lacking sufficient natural rainfall to support crops for rainfed agriculture.
The earliest known use of the technology dates to the 6th millennium BCE in Khuzistan in the south-west of present-day Iran. Irrigation was used as a means of manipulation of water in the alluvial plains of the Indus valley civilization, the application of it is estimated to have begun around 4500 BC and drastically increased the size and prosperity of their agricultural settlements; the Indus Valley Civilization developed sophisticated irrigation and water-storage systems, including artificial reservoirs at Girnar dated to 3000 BCE, an early canal irrigation system from c. 2600 BCE. Large-scale agriculture was practiced, with an extensive network of canals used for the purpose of irrigation. Farmers in the Mesopotamian plain used irrigation from at least the third millennium BCE, they developed perennial irrigation watering crops throughout the growing season by coaxing water through a matrix of small channels formed in the field. Ancient Egyptians practiced basin irrigation using the flooding of the Nile to inundate land plots, surrounded by dykes.
The flood water remained until the fertile sediment had settled before the engineers returned the surplus to the watercourse. There is evidence of the ancient Egyptian pharaoh Amenemhet III in the twelfth dynasty using the natural lake of the Faiyum Oasis as a reservoir to store surpluses of water for use during dry seasons; the lake swelled annually from the flooding of the Nile. The Ancient Nubians developed a form of irrigation by using a waterwheel-like device called a sakia. Irrigation began in Nubia some time between the third and second millennia BCE, it depended upon the flood waters that would flow through the Nile River and other rivers in what is now the Sudan. In sub-Saharan Africa irrigation reached the Niger River region cultures and civilizations by the first or second millennium BCE and was based on wet-season flooding and water harvesting. Evidence of terrace irrigation occurs in pre-Columbian America, early Syria and China. In the Zana Valley of the Andes Mountains in Peru, archaeologists have found remains of three irrigation canals radiocarbon-dated from the 4th millennium BCE, the 3rd millennium BCE and the 9th century CE.
These canals provide the earliest record of irrigation in the New World. Traces of a canal dating from the 5th millennium BCE were found under the 4th-millennium canal. Ancient Persia used irrigation as far back as the 6th millennium BCE to grow barley in areas with insufficient natural rainfall; the Qanats, developed in ancient Persia about 800 BCE, are among the oldest known irrigation methods still in use today. They are now found in the Middle East and North Africa; the system comprises a network of vertical wells and sloping tunnels driven into the sides of cliffs and of steep hills to tap groundwater. The noria, a water wheel with clay pots around the rim powered by the flow of the stream, first came into use at about this time among Roman settlers in North Africa. By 150 BCE the pots were fitted with valves to allow smoother filling as they were forced into the water; the irrigation works of ancient Sri Lanka, the earliest dating from about 300 BCE in the reign of King Pandukabhaya, under continuous development for the next thousand years, were one of the most complex irrigation systems of the ancient world.
In addition to underground canals, the Sinhalese were the first to build artificial reservoirs to store water. These reservoirs and canal systems were used to irrigate paddy fields, which require a lot of water to cultivate. Most of these irrigation systems still exist undamaged up to now, in Anuradhapura and Polonnaruwa, because of the advanced and precise engineering; the system was further extended during the reign of King Parakrama Bahu. The oldest known hydraulic engineers of China were Sunshu Ao of the Spring and Autumn period and Ximen Bao of the Warring States period, both of whom worked on large irrigation projects. In the Sichuan region belonging to the state of Qin of ancient China, the Dujiangyan Irrigation System devised by the Qin Chinese hydrologist and irrigation engineer Li Bing was built in 256 BCE to irrigate a vast area of farmland that today still supplies water. By the 2nd century AD, during the Han Dynasty, the Chinese used chain pumps which lifted water from a lower elevation to a higher one.
These were powered by manual foot-pedal, hydraulic waterwheels, or rotating mechanical wheels pulled by oxen. The water was used for public works, providing water for urban residential quarters and palace gardens, bu
A stream is a body of water with surface water flowing within the bed and banks of a channel. The stream encompasses surface and groundwater fluxes that respond to geological, geomorphological and biotic controls. Depending on its location or certain characteristics, a stream may be referred to by a variety of local or regional names. Long large streams are called rivers. Streams are important as conduits in the water cycle, instruments in groundwater recharge, corridors for fish and wildlife migration; the biological habitat in the immediate vicinity of a stream is called a riparian zone. Given the status of the ongoing Holocene extinction, streams play an important corridor role in connecting fragmented habitats and thus in conserving biodiversity; the study of streams and waterways in general is known as surface hydrology and is a core element of environmental geography. Brook A stream smaller than a creek one, fed by a spring or seep, it is small and forded. A brook is characterised by its shallowness.
Creek In North America and New Zealand, a small to medium-sized natural stream. Sometimes navigable by motor craft and may be intermittent. In parts of Maryland, New England, the UK and India, a tidal inlet in a salt marsh or mangrove swamp, or between enclosed and drained former salt marshes or swamps. In these cases, the stream is the tidal stream, the course of the seawater through the creek channel at low and high tide. River A large natural stream, which may be a waterway. Runnel the linear channel between the parallel ridges or bars on a shoreline beach or river floodplain, or between a bar and the shore. Called a swale. Tributary A contributory stream, or a stream which does not reach a static body of water such as a lake or ocean, but joins another river. Sometimes called a branch or fork. There are a number of regional names for a stream. Allt is used in Highland Scotland. Beck is used in Lincolnshire to Cumbria in areas which were once occupied by the Danes and Norwegians. Bourne or winterbourne is used in the chalk downland of southern England.
Brook. Burn is used in North East England. Gill or ghyll is seen in Surrey influenced by Old Norse; the variant "ghyll" is used in the Lake District and appears to have been an invention of William Wordsworth. Nant is used in Wales. Rivulet is a term encountered in Victorian era publications. Stream Syke is used in lowland Cumbria for a seasonal stream. Branch is used to name streams in Virginia. Creek is common throughout the United States, as well as Australia. Falls is used to name streams in Maryland, for streams/rivers which have waterfalls on them if such falls have a small vertical drop. Little Gunpowder Falls and The Jones Falls are rivers named in this manner, unique to Maryland. Kill in New York, Pennsylvania and New Jersey comes from a Dutch language word meaning "riverbed" or "water channel", can be used for the UK meaning of'creek'. Run in Ohio, Michigan, New Jersey, Virginia, or West Virginia can be the name of a stream. Run in Florida is the name given to streams coming out of small natural springs.
River is used for larger springs like the Silver Rainbow River. Stream and brook are used in Midwestern states, Mid-Atlantic states, New England. Bar A shoal that develops in a stream as sediment is deposited as the current slows or is impeded by wave action at the confluence. Bifurcation A fork into two or more streams. Channel A depression created by constant erosion. Confluence The point at which the two streams merge. If the two tributaries are of equal size, the confluence may be called a fork. Drainage basin The area of land. A large drainage basin such as the Amazon River contains many smaller drainage basins. Floodplain Lands adjacent to the stream that are subject to flooding when a stream overflows its banks. Gaging station A site along the route of a stream or river, used for reference marking or water monitoring. Headwaters The part of a stream or river proximate to its source; the word is most used in the plural where there is no single point source. Knickpoint The point on a stream's profile where a sudden change in stream gradient occurs.
Mouth The point at which the stream discharges via an estuary or delta, into a static body of water such as a lake or ocean. Pool A segment where the water is deeper and slower moving. Rapids A turbulent, fast-flowing stretch of a stream or river. Riffle A segment where the flow is shallower and more turbulent. River A large natural stream, which may be a waterway. Run A somewhat smoothly flowing segment of the stream. Source The spring, or other point of origin of a stream. Spring The point at which a stream emerges from an underground course through unconsolidated sediments or through caves. A stream can with caves, flow aboveground for part of its course, underground for part of its course. Stream bed The bottom of a stream. Stream corridor Stream, its floodplains, the transitional upland fringe Streamflow The water moving through a stream channel. Thalweg The river's longitudinal section, or the line joining the deepest point in the channel at each stage from source to mouth. Waterfall or cascade The fall of water where the stream goes over a sudden drop called a knickpoint.
The stream expends kinetic energy in "trying" to eliminate the
Gautama Buddha known as Siddhārtha Gautama in Sanskrit or Siddhattha Gotama in Pali, Shakyamuni Buddha, or the Buddha, after the title of Buddha, was a monk, sage, philosopher and religious leader on whose teachings Buddhism was founded. He is believed to have lived and taught in the northeastern part of ancient India sometime between the 6th and 4th centuries BCE. Gautama taught a Middle Way between sensual indulgence and the severe asceticism found in the śramaṇa movement common in his region, he taught throughout other regions of eastern India such as Magadha and Kosala. Gautama is the primary figure in Buddhism, he is believed by Buddhists to be an enlightened teacher who attained full Buddhahood and shared his insights to help sentient beings end rebirth and suffering. Accounts of his life and monastic rules are believed by Buddhists to have been summarised after his death and memorized by his followers. Various collections of teachings attributed to him were passed down by oral tradition and first committed to writing about 400 years later.
Scholars are hesitant to make unqualified claims about the historical facts of the Buddha's life. Most people accept that the Buddha lived and founded a monastic order during the Mahajanapada era during the reign of Bimbisara, the ruler of the Magadha empire, died during the early years of the reign of Ajatasatru, the successor of Bimbisara, thus making him a younger contemporary of Mahavira, the Jain tirthankara. While the general sequence of "birth, renunciation, search and liberation, death" is accepted, there is less consensus on the veracity of many details contained in traditional biographies; the times of Gautama's birth and death are uncertain. Most historians in the early 20th century dated his lifetime as c. 563 BCE to 483 BCE. More his death is dated between 411 and 400 BCE, while at a symposium on this question held in 1988, the majority of those who presented definite opinions gave dates within 20 years either side of 400 BCE for the Buddha's death; these alternative chronologies, have not been accepted by all historians.
The evidence of the early texts suggests that Siddhārtha Gautama was born into the Shakya clan, a community, on the periphery, both geographically and culturally, of the eastern Indian subcontinent in the 5th century BCE. One of his usual names was "Sakamuni" or "Sakyamunī", it was either a small republic, or an oligarchy, his father was an elected chieftain, or oligarch. According to the Buddhist tradition, Gautama was born in Lumbini, now in modern-day Nepal, raised in the Shakya capital of Kapilvastu, which may have been either in what is present day Tilaurakot, Nepal or Piprahwa, India. According to Buddhist tradition, he obtained his enlightenment in Bodh Gaya, gave his first sermon in Sarnath, died in Kushinagar. Apart from the Vedic Brahmins, the Buddha's lifetime coincided with the flourishing of influential Śramaṇa schools of thought like Ājīvika, Cārvāka, Ajñana. Brahmajala Sutta records sixty-two such schools of thought. In this context, a śramaṇa refers to one who toils, or exerts themselves.
It was the age of influential thinkers like Mahavira, Pūraṇa Kassapa, Makkhali Gosāla, Ajita Kesakambalī, Pakudha Kaccāyana, Sañjaya Belaṭṭhaputta, as recorded in Samaññaphala Sutta, whose viewpoints the Buddha most must have been acquainted with. Indeed and Moggallāna, two of the foremost disciples of the Buddha, were the foremost disciples of Sañjaya Belaṭṭhaputta, the sceptic. There is philological evidence to suggest that the two masters, Alara Kalama and Uddaka Ramaputta, were indeed historical figures and they most taught Buddha two different forms of meditative techniques. Thus, Buddha was just one of the many śramaṇa philosophers of that time. In an era where holiness of person was judged by their level of asceticism, Buddha was a reformist within the śramaṇa movement, rather than a reactionary against Vedic Brahminism; the life of the Buddha coincided with the Achaemenid conquest of the Indus Valley during the rule of Darius I from about 517/516 BCE. This Achaemenid occupation of the areas of Gandhara and Sindh, to last for about two centuries, was accompanied by the introduction of Achaemenid religions, reformed Mazdaism or early Zoroastrianism, to which Buddhism might have in part reacted.
In particular, the ideas of the Buddha may have consisted of a rejection of the "absolutist" or "perfectionist" ideas contained in these Achaemenid religions. No written records about Gautama were found from his lifetime or from the one or two centuries thereafter. In the middle of the 3rd century BCE, several Edicts of Ashoka mention the Buddha, Ashoka's Rummindei Minor Pillar Edict commemorates the Emperor's pilgrimage to Lumbini as the Buddha's birthplace. Another one of his edicts mentions the titles of several Dhamma texts, establishing the existence of a written Buddhist tradition at least by the time of the Maurya era; these texts may be the precursor of the Pāli Canon. "Sakamuni" in mentioned in the reliefs of Bharhut, dated to circa 100 BCE, in relation with his illumination and the Bodhi tree, with the inscription Bhagavato Sakamunino Bodho. The oldest surviving Buddhist manuscripts are the Gandhāran Buddhist texts, repor
Rain is liquid water in the form of droplets that have condensed from atmospheric water vapor and become heavy enough to fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth, it provides suitable conditions for many types of ecosystems, as well as water for hydroelectric power plants and crop irrigation. The major cause of rain production is moisture moving along three-dimensional zones of temperature and moisture contrasts known as weather fronts. If enough moisture and upward motion is present, precipitation falls from convective clouds such as cumulonimbus which can organize into narrow rainbands. In mountainous areas, heavy precipitation is possible where upslope flow is maximized within windward sides of the terrain at elevation which forces moist air to condense and fall out as rainfall along the sides of mountains. On the leeward side of mountains, desert climates can exist due to the dry air caused by downslope flow which causes heating and drying of the air mass.
The movement of the monsoon trough, or intertropical convergence zone, brings rainy seasons to savannah climes. The urban heat island effect leads to increased rainfall, both in amounts and intensity, downwind of cities. Global warming is causing changes in the precipitation pattern globally, including wetter conditions across eastern North America and drier conditions in the tropics. Antarctica is the driest continent; the globally averaged annual precipitation over land is 715 mm, but over the whole Earth it is much higher at 990 mm. Climate classification systems such as the Köppen classification system use average annual rainfall to help differentiate between differing climate regimes. Rainfall is measured using rain gauges. Rainfall amounts can be estimated by weather radar. Rain is known or suspected on other planets, where it may be composed of methane, sulfuric acid, or iron rather than water. Air contains water vapor, the amount of water in a given mass of dry air, known as the mixing ratio, is measured in grams of water per kilogram of dry air.
The amount of moisture in air is commonly reported as relative humidity. How much water vapor a parcel of air can contain before it becomes saturated and forms into a cloud depends on its temperature. Warmer air can contain more water vapor than cooler air before becoming saturated. Therefore, one way to saturate a parcel of air is to cool it; the dew point is the temperature. There are four main mechanisms for cooling the air to its dew point: adiabatic cooling, conductive cooling, radiational cooling, evaporative cooling. Adiabatic cooling occurs when air expands; the air can rise due to convection, large-scale atmospheric motions, or a physical barrier such as a mountain. Conductive cooling occurs when the air comes into contact with a colder surface by being blown from one surface to another, for example from a liquid water surface to colder land. Radiational cooling occurs due to the emission of infrared radiation, either by the air or by the surface underneath. Evaporative cooling occurs when moisture is added to the air through evaporation, which forces the air temperature to cool to its wet-bulb temperature, or until it reaches saturation.
The main ways water vapor is added to the air are: wind convergence into areas of upward motion, precipitation or virga falling from above, daytime heating evaporating water from the surface of oceans, water bodies or wet land, transpiration from plants, cool or dry air moving over warmer water, lifting air over mountains. Water vapor begins to condense on condensation nuclei such as dust and salt in order to form clouds. Elevated portions of weather fronts force broad areas of upward motion within the Earth's atmosphere which form clouds decks such as altostratus or cirrostratus. Stratus is a stable cloud deck which tends to form when a cool, stable air mass is trapped underneath a warm air mass, it can form due to the lifting of advection fog during breezy conditions. Coalescence occurs. Air resistance causes the water droplets in a cloud to remain stationary; when air turbulence occurs, water droplets collide. As these larger water droplets descend, coalescence continues, so that drops become heavy enough to overcome air resistance and fall as rain.
Coalescence happens most in clouds above freezing, is known as the warm rain process. In clouds below freezing, when ice crystals gain enough mass they begin to fall; this requires more mass than coalescence when occurring between the crystal and neighboring water droplets. This process is temperature dependent, as supercooled water droplets only exist in a cloud, below freezing. In addition, because of the great temperature difference between cloud and ground level, these ice crystals may melt as they fall and become rain. Raindrops have sizes ranging from 0.1 to 9 mm mean diameter. Smaller drops are called cloud droplets, their shape is spherical; as a raindrop increases in size, its shape becomes more oblate, with its largest cross-section facing the oncoming airflow. Large rain drops become flattened on the bottom, like hamburger buns. Contrary to popular beli
The betel is a vine belonging to the Piperaceae family, which includes pepper and kava. Betel leaf is consumed in Asia, elsewhere in the world by some Asian emigrants, as betel quid or in paan, with Areca nut and/or tobacco. In India and Sri Lanka a sheaf of betel leaves is traditionally offered as a mark of respect and auspicious beginnings. Occasions include greeting elders at wedding ceremonies, celebrating the New Year, offering payment to Ayurvedic physicians and astrologers; the betel plant is an evergreen perennial, with white catkin. The betel plant originated in South East Asia. Betel, derived from the word vettila, via Portuguese; the betel leaf is cultivated in South and Southeast Asia, from Pakistan to Papua New Guinea. It needs a long pole for support. Betel requires well-drained fertile soil. Waterlogged and alkali soils are unsuitable for its cultivation. In Bangladesh, farmers called; the barouj is fenced with bamboo coconut leaves. The soil is plowed into furrows of 10 to 15 metres' length, 75 centimetres in width and 75 centimetres' depth.
Oil cakes and leaves are incorporated with the topsoil of the furrows and wood ash. The cuttings are planted at the beginning of the monsoon season. Proper shade and irrigation are essential for the successful cultivation of this crop. Betel needs moist soil, but there should not be excessive moisture. Irrigation is frequent and light, standing water should not remain for more than half an hour. Dried leaves and wood ash are applied to the furrows at fortnightly intervals and cow dung slurry is sprinkled. Application of different kinds of leaves at monthly intervals is believed advantageous for the growth of the betel. In 3 to 6 months the vines reach 150 to 180 centimeters in height and they will branch. Harvest begins, with the farmer plucking its petiole with his right thumb; the harvest lasts 15 days to one month. Betel plant has made its way to research labs of many Bangladesh chemical and food nutrition companies; the harvested leaves are consumed locally and exported to other parts of Asia, the Middle East and the Americas.
Betel is cultivated as an important crop in rural Bangladesh. The primary use of betel leaf is as a wrapper for the chewing of areca nut or tobacco where it is used to add flavour, it may be used in cooking raw, for its peppery taste. Some reports may suggest that betel leaf by itself has adverse health effects, in part because of tannins delivered by the leaf and for reasons not understood. For example, one research paper studied chromosome damaging effect of betel leaf in human leukocyte cultures; these researchers report an increase in the frequency of chromatid aberrations when the leaf extract was added to cultures. Another scientific study from Japan indicates that the lab rats that ate a mixture of betel leaf and areca nuts all had severe thickening of the upper digestive tract whereas after undergoing a diet of betel leaves alone, only one laboratory rat ended up having a forestomach papilloma. Betel leaf extract alone has not been shown to cause significant side effects, but there are side effects associated with the use of betel quid.
Betel vines are cultivated throughout southeast Asia in plots whose area is 20 to 2000 square metres. Malaysian farmers cultivate four types of betel plants: sirih India, sirih Melayu, sirih Cina and sirih Udang; the harvest is sold in bundles of 10 leaves, each bundle costing in 2011 between MYR 0.30 to 0.50. In Sri Lanka, betel is grown all over the country but the commercial production of betel, with bigger leaves with dark green colour combined with thickness, known as “kalu bulath” is confined to a few districts such as Kurunagala, Kegalle and Colombo; these are sold at a whole seller lots of 1000 leaves. In a report published by the United Nations Food and Agriculture Organization, a successful betel farm in Sri Lanka can provide a supplemental income to a farmer by providing six days of work every six months and net income when the leaf prices are attractive; the FAO study found the successful farm's yield to be 18,000 leaves per 150 square feet. The additional salary and income to the Sri Lankan betel grower, assuming he or she provides all needed labor and keeps all net profit, to be SL Rs. 1635 per 150 square feet of betel farm every 6 months.
If the farmer hires outside labor to tend the betel vines, harvest the crop, the FAO found the net income to the betel farm owner to be SL Rs. 735 per 150 square feet of betel farm every 6 months. According to FAO, the market prices for betel leaves vary with wet and dry season in Sri Lanka, in 2010 averaged SL Rs. 200–400 per 1000 leaves. The FAO study assumes no losses from erratic weather, no losses during storage and transportation of perishable betel leaves; these losses are between 35% to 70%. In Bangladesh, betel leaf farming yields vary by vine variety. In one region where betel leaf cultivation is the main source of income for farmers, a total of 2,825 hectares of land is dedicated to betel vine farming; the average production cost for these betel farms in Bangladesh are about Tk 300,000 per hectare, the farm owners can earn a profit of over Tk 100,000 per hectare ($1334 per hectare, $5