Snow refers to forms of ice crystals that precipitate from the atmosphere and undergo changes on the Earth's surface. It pertains to frozen crystalline water throughout its life cycle, starting when, under suitable conditions, the ice crystals form in the atmosphere, increase to millimeter size and accumulate on surfaces metamorphose in place, melt, slide or sublimate away. Snowstorms develop by feeding on sources of atmospheric moisture and cold air. Snowflakes nucleate around particles in the atmosphere by attracting supercooled water droplets, which freeze in hexagonal-shaped crystals. Snowflakes take on a variety of shapes, basic among these are platelets, needles and rime; as snow accumulates into a snowpack, it may blow into drifts. Over time, accumulated snow metamorphoses, by sintering and freeze-thaw. Where the climate is cold enough for year-to-year accumulation, a glacier may form. Otherwise, snow melts seasonally, causing runoff into streams and rivers and recharging groundwater. Major snow-prone areas include the polar regions, the upper half of the Northern Hemisphere and mountainous regions worldwide with sufficient moisture and cold temperatures.
In the Southern Hemisphere, snow is confined to mountainous areas, apart from Antarctica. Snow affects such human activities as transportation: creating the need for keeping roadways and windows clear. Snow affects ecosystems, as well, by providing an insulating layer during winter under which plants and animals are able to survive the cold. Snow develops in clouds; the physics of snow crystal development in clouds results from a complex set of variables that include moisture content and temperatures. The resulting shapes of the falling and fallen crystals can be classified into a number of basic shapes and combinations, thereof; some plate-like and stellar-shaped snowflakes can form under clear sky with a cold temperature inversion present. Snow clouds occur in the context of larger weather systems, the most important of, the low pressure area, which incorporate warm and cold fronts as part of their circulation. Two additional and locally productive sources of snow are lake-effect storms and elevation effects in mountains.
Mid-latitude cyclones are low pressure areas which are capable of producing anything from cloudiness and mild snow storms to heavy blizzards. During a hemisphere's fall and spring, the atmosphere over continents can be cold enough through the depth of the troposphere to cause snowfall. In the Northern Hemisphere, the northern side of the low pressure area produces the most snow. For the southern mid-latitudes, the side of a cyclone that produces the most snow is the southern side. A cold front, the leading edge of a cooler mass of air, can produce frontal snowsqualls—an intense frontal convective line, when temperature is near freezing at the surface; the strong convection that develops has enough moisture to produce whiteout conditions at places which line passes over as the wind causes intense blowing snow. This type of snowsquall lasts less than 30 minutes at any point along its path but the motion of the line can cover large distances. Frontal squalls may form a short distance ahead of the surface cold front or behind the cold front where there may be a deepening low pressure system or a series of trough lines which act similar to a traditional cold frontal passage.
In situations where squalls develop post-frontally it is not unusual to have two or three linear squall bands pass in rapid succession only separated by 25 miles with each passing the same point in 30 minutes apart. In cases where there is a large amount of vertical growth and mixing the squall may develop embedded cumulonimbus clouds resulting in lightning and thunder, dubbed thundersnow. A warm front can produce snow for a period, as warm, moist air overrides below-freezing air and creates precipitation at the boundary. Snow transitions to rain in the warm sector behind the front. Lake-effect snow is produced during cooler atmospheric conditions when a cold air mass moves across long expanses of warmer lake water, warming the lower layer of air which picks up water vapor from the lake, rises up through the colder air above, freezes and is deposited on the leeward shores; the same effect occurs over bodies of salt water, when it is termed ocean-effect or bay-effect snow. The effect is enhanced when the moving air mass is uplifted by the orographic influence of higher elevations on the downwind shores.
This uplifting can produce narrow but intense bands of precipitation, which deposit at a rate of many inches of snow each hour resulting in a large amount of total snowfall. The areas affected by lake-effect snow are called snowbelts; these include areas east of the Great Lakes, the west coasts of northern Japan, the Kamchatka Peninsula in Russia, areas near the Great Salt Lake, Black Sea, Caspian Sea, Baltic Sea, parts of the northern Atlantic Ocean. Orographic or relief snowfall is caused when masses of air pushed by wind are forced up the side of elevated land formations, such as large mountains; the lifting of air up the side of a mountain or range results in adiabatic cooling, condensation and precipitation. Moisture is removed by orographic lift, leaving drier, warmer air on the leeward side; the resulting enhanced productivity of snow fall and the decrease in temperature with elevation means that snow depth
Hibbertia, or Guinea flower, is a genus of trees, trailing shrubs and climbers of the family Dilleniaceae. The five-petalled flowers of all species are varying shades of yellow, with the exception of H. stellaris, H. miniata and H. selkii, a named species from the Stirling Ranges, which all have orange flowers. Around 150 species occur in Australia of which two are found in New Guinea. Additionally, 24 species occur in New Caledonia, one of, found in Fiji, one other species is endemic to Madagascar; the genus is being revised by Helmut Toelken of the South Australian Herbarium. The genus takes its name from an eminent English merchant and amateur botanist. Given the similarity in flower colour and shape, the number of stamens is a useful method of identification as this can vary from 4 to about 200 depending on species. Species include: Hibbertia amplexicaulis Hibbertia aspera - Rough Guinea-flower Hibbertia banksii Hibbertia basaltica Hibbertia bracteata Hibbertia cistiflora - Rock rose Guinea-flower Hibbertia cuneiformis - Cut-leaf hibbertia Hibbertia dentata - Twining Guinea-flower Hibbertia diffusa Hibbertia empetrifolia - Tangled Guinea-flower Hibbertia ericifolia Hibbertia fasciculata Hibbertia furfuracea Hibbertia grossulariifolia - Gooseberry-leaved Guinea-flower Hibbertia hermanniifolia Hibbertia hirta Hibbertia hypericoides - Yellow buttercups Hibbertia incana - Prickly Guinea-flower Hibbertia linearis Hibbertia longifolia Hibbertia marginata Hibbertia miniata - Orange Guinea-flower Hibbertia obtusifolia - Hoary Guinea-flower Hibbertia pedunculata - Stalked Guinea-flower Hibbertia procumbens Hibbertia prostrata - Bundled Guinea-flower Hibbertia riparia - Erect Guinea-flower Hibbertia saligna Hibbertia scandens – Climbing Guinea-flower or snake vine Hibbertia selkii Hibbertia sericea - Silky Guinea-flower Hibbertia serpyllifolia Hibbertia serrata Hibbertia stellaris – Star Guinea-flower Hibbertia truncata - Port Campbell Guinea-flower Hibbertia vestita - Hairy Guinea-flower
Monsoon is traditionally defined as a seasonal reversing wind accompanied by corresponding changes in precipitation, but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea. The term monsoon is used to refer to the rainy phase of a seasonally changing pattern, although technically there is a dry phase; the term is sometimes incorrectly used for locally heavy but short-term rains, although these rains meet the dictionary definition of monsoon. The major monsoon systems of the world consist of the West Asia-Australian monsoons; the inclusion of the North and South American monsoons with incomplete wind reversal has been debated. The term was first used in English in British India and neighbouring countries to refer to the big seasonal winds blowing from the Bay of Bengal and Arabian Sea in the southwest bringing heavy rainfall to the area; the English monsoon came from Portuguese monção from Arabic mawsim, "perhaps via early modern Dutch monson."
Strengthening of the Asian monsoon has been linked to the uplift of the Tibetan Plateau after the collision of the Indian sub-continent and Asia around 50 million years ago. Because of studies of records from the Arabian Sea and that of the wind-blown dust in the Loess Plateau of China, many geologists believe the monsoon first became strong around 8 million years ago. More studies of plant fossils in China and new long-duration sediment records from the South China Sea led to a timing of the monsoon beginning 15–20 million years ago and linked to early Tibetan uplift. Testing of this hypothesis awaits deep ocean sampling by the Integrated Ocean Drilling Program; the monsoon has varied in strength since this time linked to global climate change the cycle of the Pleistocene ice ages. A study of marine plankton suggested that the Indian Monsoon strengthened around 5 million years ago. During ice periods, the sea level fell and the Indonesian Seaway closed; when this happened, cold waters in the Pacific were impeded from flowing into the Indian Ocean.
It is believed that the resulting increase in sea surface temperatures in the Indian Ocean increased the intensity of monsoons. Five episodes during the Quaternary at 2.22 Ma, 1.83 Ma, 0.68 Ma, 0.45 Ma and 0.04 Ma were identified which showed a weakening of Leeuwin Current. The weakening of the LC would have an effect on the sea surface temperature field in the Indian Ocean, as the Indonesian through flow warms the Indian Ocean, thus these five intervals could be those of considerable lowering of SST in the Indian Ocean and would have influenced Indian monsoon intensity. During the weak LC, there is the possibility of reduced intensity of the Indian winter monsoon and strong summer monsoon, because of change in the Indian Ocean dipole due to reduction in net heat input to the Indian Ocean through the Indonesian through flow, thus a better understanding of the possible links between El Niño, Western Pacific Warm Pool, Indonesian Throughflow, wind pattern off western Australia, ice volume expansion and contraction can be obtained by studying the behaviour of the LC during Quaternary at close stratigraphic intervals.
The impact of monsoon on the local weather is different from place to place. In some places there is just a likelihood of having a little less rain. In other places, quasi semi-deserts are turned into vivid green grasslands where all sorts of plants and crops can flourish; the Indian Monsoon turns large parts of India from a kind of semi-desert into green lands. See photos only taken 3 months apart in the Western Ghats. In places like this it is crucial for farmers to have the right timing for putting the seeds on the fields, as it is essential to use all the rain, available for growing crops. Monsoons are large-scale sea breezes which occur when the temperature on land is warmer or cooler than the temperature of the ocean; these temperature imbalances happen. Over oceans, the air temperature remains stable for two reasons: water has a high heat capacity, because both conduction and convection will equilibrate a hot or cold surface with deeper water. In contrast, dirt and rocks have lower heat capacities, they can only transmit heat into the earth by conduction and not by convection.
Therefore, bodies of water stay at a more temperature, while land temperature are more variable. During warmer months sunlight heats the surfaces of both land and oceans, but land temperatures rise more quickly; as the land's surface becomes warmer, the air above it expands and an area of low pressure develops. Meanwhile, the ocean remains at a lower temperature than the land, the air above it retains a higher pressure; this difference in pressure causes sea breezes to blow from the ocean to the land, bringing moist air inland. This moist air rises to a higher altitude over land and it flows back toward the ocean. However, when the air rises, while it is still over the land, the air cools; this decreases the air's ability to hold water, this causes precipitation over the land. This is. In the colder months, the cycle is reversed; the land cools faster than the oceans and the air over the land has higher pressure than air over the ocean. This causes the air over the land to flow to the ocean; when humid air rises over the ocean, it cools, this causes precipitation over the oceans.
(The cool air flows towards the land to complete the cy
An orogeny is an event that leads to both structural deformation and compositional differentiation of the Earth's lithosphere at convergent plate margins. An orogen or orogenic belt develops when a continental plate crumples and is pushed upwards to form one or more mountain ranges. Orogeny is the primary mechanism; the word "orogeny" comes from Ancient Greek. Although it was used before him, the term was employed by the American geologist G. K. Gilbert in 1890 to describe the process of mountain building as distinguished from epeirogeny; the formation of an orogen can be accomplished by the tectonic processes such as oceanic subduction or continental subduction convergence of two or more continents for collisional orogeny). Orogeny produces long arcuate structures, known as orogenic belts. Orogenic belts consist of long parallel strips of rock exhibiting similar characteristics along the length of the belt. Although orogenic belts are associated with subduction zones, subduction tectonism may be ongoing or past processes.
The subducting tectonism would consume crust, thicken lithosphere, produce earthquake and volcanoes, build island arcs in many cases. Geologists attribute the arcuate structure to the rigidity of the descending plate, island arc cusps relate to tears in the descending lithosphere; these island arcs may be added to a continental margin during an accretionary orogeny. On the other hand, subduction zones may be reworked at a time due to lithospheric rifting, leading to amphibolite to granulite facies metamorphism of the thinned orogenic crust; the processes of orogeny can take tens of millions of years and build mountains from plains or from the seabed. The topographic height of orogenic mountains is related to the principle of isostasy, that is, a balance of the downward gravitational force upon an upthrust mountain range and the buoyant upward forces exerted by the dense underlying mantle. Rock formations that undergo orogeny are deformed and undergo metamorphism. Orogenic processes may push buried rocks to the surface.
Sea-bottom and near-shore material may cover all of the orogenic area. If the orogeny is due to two continents colliding high mountains can result. An orogenic event may be studied: as a tectonic structural event, as a geographical event, as a chronological event. Orogenic events: cause distinctive structural phenomena related to tectonic activity affect rocks and crust in particular regions, happen within a specific period In general, there are two main types of orogens at convergent plate margins: accretionary orogens, which were produced by subduction of one oceanic plate beneath one continental plate to result in either continental arc magmatism or the accretion of island arc terranes to continental margins. An orogeny produces an orogen, but a range-foreland basin system is only produced on passive plate margins; the foreland basin forms ahead of the orogen due to loading and resulting flexure of the lithosphere by the developing mountain belt. A typical foreland basin is subdivided into a wedge-top basin above the active orogenic wedge, the foredeep beyond the active front, a forebulge high of flexural origin and a back-bulge area beyond, although not all of these are present in all foreland-basin systems.
The basin migrates with the orogenic front and early deposited foreland basin sediments become progressively involved in folding and thrusting. Sediments deposited in the foreland basin are derived from the erosion of the uplifting rocks of the mountain range, although some sediments derive from the foreland; the fill of many such basins shows a change in time from deepwater marine through shallow water to continental sediments. Although orogeny involves plate tectonics, the tectonic forces result in a variety of associated phenomena, including crustal deformation, crustal thickening, crustal thinning and crustal melting as well as magmatism and mineralization. What happens in a specific orogen depends upon the strength and rheology of the continental lithosphere, how these properties change during orogenesis. In addition to orogeny, the orogen is subject to other processes, such as erosion; the sequence of repeated cycles of sedimentation and erosion, followed by burial and metamorphism, by crustal anatexis to form granitic batholiths and tectonic uplift to form mountain chains, is called the orogenic cycle.
For example, the Caledonian Orogeny refers to a series of tectonic events due to the continental collision of Laurentia with Eastern Avalonia and other former fragments of Gondwana in the Early Paleozoic. The Caledonian Orogen resulted from these events and various others that are part of its peculiar orogenic cycle. In summary, an orogeny is an episode of deformation and magmatism at convergent plate margins, during which many geological processes play a role at convergent plate margins; every orogeny has its own orogenic cycle, but composite orogenesis is common at convergent plate margins. Erosion represents a subsequent phase of the orogenic cycle. Erosion removes much of the mountains
An amphitheatre or amphitheater is an open-air venue used for entertainment and sports. The term derives from the ancient Greek ἀμφιθέατρον, from ἀμφί, meaning "on both sides" or "around" and θέατρον, meaning "place for viewing". Ancient Roman amphitheatres were oval or circular in plan, with seating tiers that surrounded the central performance area, like a modern open-air stadium. In contrast both ancient Greek and ancient Roman theatres were built in a semicircle, with tiered seating rising on one side of the performance area. In modern usage, an "amphitheatre" may consist of theatre-style stages with spectator seating on only one side, theatres in the round, stadia. Natural formations of similar shape are sometimes known as natural amphitheatres. Ancient Roman amphitheatres were major public venues, circular or oval in plan, with perimeter seating tiers, they were used for events such as gladiator combats, chariot races and executions. About 230 Roman amphitheatres have been found across the area of the Roman Empire.
Their typical shape and name distinguish them from Roman theatres, which are more or less semicircular in shape. The earliest Roman amphitheatres date from the middle of the first century BCE, but most were built under Imperial rule, from the Augustan period onwards. Imperial amphitheatres were built throughout the Roman empire; the most elaborate featured multi-storeyed, arcaded façades and were elaborately decorated with marble and statuary. After the end of gladiatorial games in the 5th century and of staged animal hunts in the 6th, most amphitheatres fell into disrepair, their materials were recycled. Some were razed, others were converted into fortifications. A few continued as convenient open meeting places. A natural amphitheatre is a performance space located in a spot where a steep mountain or a particular rock formation amplifies or echoes sound, making it ideal for musical and theatrical performances. An amphitheatre can be occurring formations which would be ideal for this purpose if no theatre has been constructed there.
Notable natural amphitheatres include the Drakensberg amphitheatre in South Africa, Slane Castle in Ireland, the Supernatural Amphitheatre in Australia, the Red Rocks and Gorge amphitheatres in the western United States. Arena Stadium Thingplatz List of Roman amphitheatres List of contemporary amphitheatres List of indoor arenas List of ancient Greek theatres Roman theatre Bomgardner, David Lee; the Story of the Roman Amphitheatre. Routledge. ISBN 0-415-16593-8
Callitris is a genus of coniferous trees in the Cupressaceae. There are 16 recognized species in the genus, of which 13 are native to Australia and the other three native to New Caledonia. Traditionally, the most used common name is cypress-pine, a name shared by some species of the related genus Actinostrobus, they are small to large shrubs, reaching 5 -- 25 m tall. The leaves are scale-like, but young seedlings have needle-like leaves. The scales are arranged in alternating whorls of three; the male cones are small, 3–6 mm long, are located at the tips of the twigs. The female cones start out inconspicuous, maturing in 18–20 months to 1–3 cm long and wide, globular to ovoid, with six overlapping, woody scales, arranged in two whorls of three; the cones remain closed on the trees for many years, opening only after being scorched by a bushfire. The genus is divided with the atypical C. macleayana in sect. Octoclinis, all the other species in sect. Callitris; some botanists treat C. macleayana in a separate genus, as Octoclinis macleayana.
C. macleayana is distinct in occurring in rainforest on the east coast of Australia. The closest relatives of Callitris are Actinostrobus from southwest Western Australia, which differs in its cones having several basal whorls of small sterile scales. A 2010 study of Actinostrobus and Callitris places the three species of Actinostrobus within an expanded Callitris based on analysis of 42 morphological and anatomical characters. In 2010, early Oligocene fossilised foliage and cones of Callitris were unearthed near the Lea River in Tasmania; the fossils were given the name Callitris leaensis and represent the oldest known representative of the genus. The genus includes the following species: Callitris baileyi – SE QLD, NE NSW Callitris canescens – S WA, S SA Callitris columellaris – south-east QLD. Synonymous with C. glaucophylla, C. endlicheri and C. intratropica. Callitris drummondii – S WA Callitris endlicheri – NSW, QLD, VIC. Nom. nud. type not cited, identity uncertain. Callitris columellaris f. glauca F.
M. Bailey, described from Qld, type not located, identity uncertain. Callitris conglobata Heynh. Nom. inval. Nom. nud, described from New Holland, type not located, identity uncertain. Callitris elegans Heynh. Nom. inval. Nom. nud, described from "New Holland", type not located, identity uncertain. Callitris intermedia' R. T. Baker & H. G. Sm. Nom. inval. identity uncertain. Callitris montana Heynh. Nom. inval. Nom. nud, described from New Holland, type not located, identity uncertain. Callitris pyramidalis Sweet, nom. inval. Nom. nud, syn. Frenela pyramidalis Parl. nom. inval. Nom. nud, type not cited, identity uncertain. Callitris macrocarpa Vent. nom. inval. Nom. nud, syn Cupressus macrocarpa A. Cunn. Nom. inval. identity uncertain. The wood of cypress-pines is light and aromatic, it can be split and resists decay. It is used to make furniture and outdoor paneling, fence posts. Cypress-pines are planted as ornamental trees, but their use is restricted by the high risks imposed by their high flammability in bushfires.
A plantation of C. intratropica was established outside of Darwin for use in house construction. After Cyclone Tracey it was realised that the timber did not resist strong winds and the plantation was abandoned; the trees are now used for the production of a blue essential oil, rich in chamazulene. A number of therapeutic effects are attributed to the essential oil, including antimicrobial and anti-inflammatory effects. Gymnosperm Database - Callitris Arboretum de Villardebelle - Photos of cones
A mountain range or hill range is a series of mountains or hills ranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similarity in form and alignment that have arisen from the same cause an orogeny. Mountain ranges are formed by a variety of geological processes, but most of the significant ones on Earth are the result of plate tectonics. Mountain ranges are found on many planetary mass objects in the Solar System and are a feature of most terrestrial planets. Mountain ranges are segmented by highlands or mountain passes and valleys. Individual mountains within the same mountain range do not have the same geologic structure or petrology, they may be a mix of different orogenic expressions and terranes, for example thrust sheets, uplifted blocks, fold mountains, volcanic landforms resulting in a variety of rock types. Most geologically young mountain ranges on the Earth's land surface are associated with either the Pacific Ring of Fire or the Alpide Belt.
The Pacific Ring of Fire includes the Andes of South America, extends through the North American Cordillera along the Pacific Coast, the Aleutian Range, on through Kamchatka, Taiwan, the Philippines, Papua New Guinea, to New Zealand. The Andes is 7,000 kilometres long and is considered the world's longest mountain system; the Alpide belt includes Indonesia and Southeast Asia, through the Himalaya, Caucasus Mountains, Balkan Mountains fold mountain range, the Alps, ends in the Spanish mountains and the Atlas Mountains. The belt includes other European and Asian mountain ranges; the Himalayas contain the highest mountains in the world, including Mount Everest, 8,848 metres high and traverses the border between China and Nepal. Mountain ranges outside these two systems include the Arctic Cordillera, the Urals, the Appalachians, the Scandinavian Mountains, the Great Dividing Range, the Altai Mountains and the Hijaz Mountains. If the definition of a mountain range is stretched to include underwater mountains the Ocean Ridges form the longest continuous mountain system on Earth, with a length of 65,000 kilometres.
The mountain systems of the earth are characterized by a tree structure, where mountain ranges can contain sub-ranges. The sub-range relationship is expressed as a parent-child relationship. For example, the White Mountains of New Hampshire and the Blue Ridge Mountains are sub-ranges of the Appalachian Mountains. Equivalently, the Appalachians are the parent of the White Mountains and Blue Ridge Mountains, the White Mountains and the Blue Ridge Mountains are children of the Appalachians; the parent-child expression extends to the sub-ranges themselves: the Sandwich Range and the Presidential Range are children of the White Mountains, while the Presidential Range is parent to the Northern Presidential Range and Southern Presidential Range. The position of mountains influences climate, such as snow; when air masses move up and over mountains, the air cools producing orographic precipitation. As the air descends on the leeward side, it warms again and is drier, having been stripped of much of its moisture.
A rain shadow will affect the leeward side of a range. Mountain ranges are subjected to erosional forces which work to tear them down; the basins adjacent to an eroding mountain range are filled with sediments which are buried and turned into sedimentary rock. Erosion is at work while the mountains are being uplifted until the mountains are reduced to low hills and plains; the early Cenozoic uplift of the Rocky Mountains of Colorado provides an example. As the uplift was occurring some 10,000 feet of Mesozoic sedimentary strata were removed by erosion over the core of the mountain range and spread as sand and clays across the Great Plains to the east; this mass of rock was removed as the range was undergoing uplift. The removal of such a mass from the core of the range most caused further uplift as the region adjusted isostatically in response to the removed weight. Rivers are traditionally believed to be the principal cause of mountain range erosion, by cutting into bedrock and transporting sediment.
Computer simulation has shown that as mountain belts change from tectonically active to inactive, the rate of erosion drops because there are fewer abrasive particles in the water and fewer landslides. Mountains on other planets and natural satellites of the Solar System are isolated and formed by processes such as impacts, though there are examples of mountain ranges somewhat similar to those on Earth. Saturn's moon Titan and Pluto, in particular exhibit large mountain ranges in chains composed of ices rather than rock. Examples include the Mithrim Montes and Doom Mons on Titan, Tenzing Montes and Hillary Montes on Pluto; some terrestrial planets other than Earth exhibit rocky mountain ranges, such as Maxwell Montes on Venus taller than any on Earth and Tartarus Montes on Mars, Jupiter's moon Io has mountain ranges formed from tectonic processes including Boösaule Montes, Dorian Montes, Hi'iaka Montes and Euboea Montes. Peakbagger Ranges Home Page Bivouac.com