Banded iron formation

Banded iron formations are distinctive units of sedimentary rock that are always of Precambrian age. A typical banded iron formation consists of repeated, thin layers of silver to black iron oxides, either magnetite or hematite, alternating with bands of iron-poor shales and cherts red in color, of similar thickness, containing microbands of iron oxides; some of the oldest known rock formations, are associated with banded iron formations. Banded iron formations account for more than 60% of global iron reserves, can be found in Australia, Canada, Russia, South Africa and the United States; the formations are abundant around the time of the great oxygenation event, 2,400 million years ago, become less common after 1,800 mya with evidence pointing to intermittent low levels of free atmospheric oxygen. 750 million years ago new banded iron formations formed that may be associated with the theoretical Snowball Earth. The conventional hypothesis is that the banded iron layers were formed in sea water as the result of oxygen released by photosynthetic cyanobacteria.

The oxygen combined with dissolved iron in Earth's oceans to form insoluble iron oxides, which precipitated out, forming a thin layer on the ocean floor, which may have been anoxic mud. Each band is similar to a varve, to the extent that the banding is assumed to result from cyclic variations in available oxygen, it is unclear whether these banded ironstone formations were seasonal, followed some feedback oscillation in the ocean's complex system or followed some other cycle. It is assumed that the Earth started with vast amounts of iron and nickel dissolved in the world's acidic seas; as photosynthetic organisms generated oxygen, the available iron in the Earth's oceans precipitated out as iron oxides. At a suspected tipping point where the oceans became permanently oxygenated, small variations in oxygen production produced periods of free oxygen in the surface waters, alternating with periods of iron oxide deposition. BIFs occur in two forms and Superior-type. Algoma-type are smaller in size and formed in the Archean.

Algoma-type BIFs are found in volcanic rocks in greenstone belts. The formation process involves the chemical precipitation of iron in anoxic environments; when oxidized the iron would sink to the bottom of the seafloor. As the oxygen levels continuously shift, the magnetite beds interlayered with amorphous/microcrystalline quartz. Superior type are the second and larger form of BIFs, they formed during the Paleoproterozoic era, occurring on continental shelves and can be found around the world. Superior types were formed by chemical precipitation in shallow waters due to increasing ocean oxygen levels reacting with dissolved iron ions in the oceans. Under calm shallow conditions, released during photosynthesis by blue-green algae, would combine with the iron to create insoluble magnetite, which would sink and be deposited on the seafloor; until 1992 it was assumed that the rare banded iron deposits represented unusual conditions where oxygen was depleted locally. Iron-rich waters would form in isolation and subsequently come into contact with oxygenated water.

The Snowball Earth hypothesis provided an alternative explanation for these younger deposits. In a Snowball Earth state the continents, seas at low latitudes, were subject to a severe ice age circa 750 to 580 million years ago that nearly or depleted free oxygen. Dissolved iron accumulated in the oxygen-poor oceans. Following the thawing of the Earth, the seas became oxygenated once more causing the precipitation of the iron. An alternative mechanism for banded iron formations in the Snowball Earth era suggests the iron was deposited from metal-rich brines in the vicinity of hydrothermally active rift zones. Alternatively, some geochemists suggest that banded iron formations could form by direct oxidation of iron by microbial anoxygenic phototrophs. Banded iron formations in northern Minnesota were found directly underneath a thick layer of ejecta from the Sudbury Basin impact. At the time of formation Earth had a single supercontinent called Columbia with substantial continental shelves. An asteroid slammed into waters about 1,000 m deep some 1.85 billion years ago.

Computer models suggest that the tsunami would have been at least 1,000 metres high at the centre, 100 metres high about 3,000 kilometres away. Those immense waves and large underwater landslides triggered by the impact stirred the ocean, bringing oxygenated waters from the surface down to the ocean floor. Sediments deposited on the seafloor before the impact, including banded iron formations, contained little if any oxidized iron, but were high in reduced iron; this Fe to Fe ratio suggests that most parts of the ocean were devoid of oxygen. Marine sediments deposited after the impact included substantial amounts of Fe but little Fe; this suggests. Following the impact dissolved iron was mixed into the deepest parts of the ocean; this would have choked off most of the supply of Fe to shallower waters where banded iron formations accumulated. The geological record suggests that environmental changes were happening in oceans worldwide before the Sudbury impact; the role of the Sudbury Basin impact in temporarily shutting down band


A hotelship is a passenger ship, used for a short period as a hotel. At times when accommodation shortages can be predicted, for example during trade fairs or big events, hotelships can complement the existing permanent hotels in a flexible fashion. In Germany, hotelships are evident during trade fair periods in Frankfurt, Cologne, Düsseldorf and Hannover; the moorings are located near the town centre. During a large trade fair such as Drupa or Medica in Düsseldorf, up to 40 ships can be moored to accommodate visitors. River cruisers are used as hotelships for a limited time and intermittently. Whereas a hotel has a fixed address and is used permanently, hotelships are only in any one location for a defined duration. Ship owners and shipping companies are keen on this use of river cruisers as, unlike in the case of deep sea cruise ships, there is no seasonal transfer of ships to warmer areas; the result is therefore more efficient use of the ships outside the main cruising season. The main thoroughfares for river cruises in Europe are the rivers Rhine, Main and Elbe.

Since many cities here lie directly on the river, this is a interesting area for hotelships. Moorings are conveniently located in the city centre, for example at the Konrad Adenauer Ufer in Cologne, the Altstadtufer in Düsseldorf or the Holbeinsteg at the Nizzawerft in Frankfurt; these locations are all close to the trade fair grounds. Because of this network of inland waterways, hotelships can be positioned where and when required, without lengthy transfers; the origins of hotelships in Germany can be traced back to the 1970s. During international trade fairs it was difficult to find good quality accommodation in a convenient location because of shortages of hotel rooms. During the International Textile Trade Fair in Frankfurt, the idea was born to moor a river cruiser on the banks of the Main and thus increase bed capacity in the city centre. Today, the Frankfurt am Main harbour authorities offer moorings for hotelships on the Nizza Werft. During the last 10 years, river cruises in Europe have become a growth area of the tourism industry.

Since the completion of the Rhine-Main-Danube Canal, the fall of the Iron Curtain and the expansion of the EU, there has been a huge increase in the potential for river cruising as part of the cruising industry. River cruising has become more comfortable and so has increased in popularity, allowing it to compete with European coach tours; as a result, there has been a steady increase in the number of ships available in recent years and therefore the availability of cruise ships for use as hotelships has increased. Another reason for the increased use of hotelships is the huge peak in demand for hotel rooms in trade fair cities. Local hotels demanding increased prices during trade fair events has led to cutbacks in trade fairs or their complete withdrawal. Many visitors have stayed away or just come for the day and have been able to do so because of reduced transport costs with budget airlines or ICE train connections. Hotelships redress the balance during these temporary peaks and, in spite of criticism from local hotels, help make trade fair locations more attractive and more competitive.

Hotelships operate as a balance in the hotel market where the market is too inflexible to react to periods of high demand such as is the case during trade fairs. Additional capacity through the construction of new hotels is not always possible and indeed not always desirable since in times of low demand outside the trade fair season, this creates excess capacity; the introduction of hotelships takes account of this situation and helps to balance occasional high demand with supply. Hotelships are marketed by charter agencies who make use of accommodation made available by shipping companies such as Viking River Cruises from Luxembourg, or private independent shipping companies, their role is to charter ships and position them in the relevant cities whilst at the same time ensuring and maintaining agreed standards. The charterers keep in close contact with trade fair organisations and tourist offices in the relevant cities in order to provide hotelships as and when required. Hotelships are therefore seen as a way of accommodating more trade fair visitors in the city, rather than in outlying areas.

Guests include individual clients as well as companies who book their hotel accommodation via specialist travel agencies or directly with the local tourist office. During the 6-month season in 2008, hotelships in Germany boosted the market with an extra 100,000 beds and their turnover was about 10,000,000 Euros; this only represents a small part of the total hotel capacity in Germany. Berlin alone, for example, has a daily capacity of 97,441 beds. During the 2019–20 coronavirus outbreak, river cruise ships were used to provide nearly 1,500 beds for medical workers in the worst affected city, Wuhan. Botel Houseboat


Kalavani is a 2010 Indian Tamil-language romantic comedy film written and directed by newcomer A. Sarkunam, it stars Vimal and debutante Oviya in the lead with Saranya Ponvannan, Ganja Karuppu and Ilavarasu in supporting roles. The film was made on a shoe-string budget, released on 25 June 2010. and became a sleeper hit of 2010. The movie was remade in Kannada as Kirataka. Two villages in Thanjavur area are always at loggerheads with each other, it spills to T20 cricket match between kids from both villages. Arivazhagan aka Arikki is a wayward son of Lakshmi, in awe but at the same time fears him, her husband Ramasamy is away in Dubai, a large part of the money he sends home is taken away by Arikki using extortionist methods, such as threatening to break the TV set at home. He is yet to pass his 12th standard. Arikki spends time in bars with friends, teases girls, asks them to profess their love for him, gets into brawls after conning others, he meets Maheshwari and wants her to declare her love for him, which she confesses.

He abducts her, they marry. Her brother Ilango is a tough guy who has an axe to grind against Arikki and his gang, which leads to the twist in the climax. Ilango, fuming with rage, is out to slice him into pieces. Does he do that? If he did not how did Arikki manage to avert that? All this is answered in an interesting climax, pleasantly humorous. Vimal as Arivazhagan Oviya as Maheshwari Saranya Ponvannan as Lakshmi Ganja Karuppu as Panchayathu Ilavarasu as Ramasamy Soori as Manikandan Sujatha Sivakumar as Rajee Thirumurugan as Ilango Antony as Arikki's friend Kannan as Florist Kalaiarasan as supporting comedian The film score and soundtrack for Kalavani was composed by S. S. Kumaran; the album consists of seven tracks featuring lyrics penned by Na. Muthukumar. Kalavani opened to positive reviews. Bhamadevi Ravi from The Times of India gave 4/5 and calling it "a complete entertainer." Sify rated the movie 4 out of 5 and stated that "Kalavani is a knockout entertainer set in a rural milieu." A critic from Top10Cinema wrote that "Kalavani is a blatant revision of Bharathiraja's yesteryear films based on villager's conflicts and guy-gal falling in love."

Gautaman Bhaskaran of Hindustan Times gave it 3/5 and wrote that "Kalavani is a canvas of delightful rural romance." Following the film's success, director Gautham Menon's Photon Kathaas has acquired the film's rights to remake it other languages. It was remade in Kannada as Kirataka with Oviya being retained as the female lead. Seven years after the film's release, the Chennai branch of the Censor Board Of Film Certification was served a notice by the High Court after a minor pregnant girl told the court that she obtained inspiration from the film Kalavani; the girl's parents claimed that the censor board had acted negligently in giving the film a "U" certificate. A sequel, Kalavani 2, was announced in 2016. Kalavani on IMDb