Dinosauruse definitivno ubio asteroid

[iguana]

drasko, nikako da odgovorish na jedno pitanje koje ti postavljam stalno - autor ovog tvog chlanka navodi kao prirodne, moguce, uzrocnike, otopljavanja - vulkane, sunce i prirodne gasove. Da li postoji dokaz pojachane sunceve aktivnosti poslednjih decenija, van klasichnog perioda od 11 godina? Navedi mi neku supererupciju vulkana u poslednjih 100 godina? Kako se i koji ti prirodni gasovi oslobadjaju? Da, moze to da bude objasnjenje, ali samo ako govorimo o oslobadjanju metana iz permafrosta prilikom ZAGREVANJA I TOPLJENJA istog. Znachi prvo mora da se zagreje atmosfera pa se onda ispustaju gasovi. Shume, secha shuma jeste problem ali samo ako govorimo o ciklusu ugljen-dioksida, jer nema toliko drveca da ga vezhe tokom fotosinteze, ali shume nemogu da reshe pitanje sumporovih oksida, koji se dobijaju gorenjem nafte, uglja...

Brate, o chemu mi prichamo ovde :)

[peja_]

drago mi je sto ste svi pogledali one klipove sto sam okacio :D

bitno da serendate non stop :D

[Debeli]

аутор каже да се загрева цео Сунчев систем.

такође, раст % СО и СО2 може да буде последица, а не само узрок, раста температуре. разумемо да је све зачарани круг.

да нема Човека, пожари које гасимо сваког лета би имали 100% учинак. природа ТЕЖи леденом добу, у том смо делу циклуса. Човек то не може ни да спречи ни да осујети. "дан после сутра" долази и све да погасимо све термоелектране и аутомобиле.

[tracktorista]

ali pitanje je brze ili sporije

[bolkonski]

@Peja

Sto bi pogledao neko tvoje linkove kada su u odnosu na moje amaterski, pa nikom nista. Ovde nije rec o nauci nego o politici, a ja se pitam koliko su losi admini i moderatori na ovom forumu kada tema nije u najmanju ruku splitovana!

[Dule_smor]

ja sam hteo da splitujem temu, ali nisam imao zivaca da odvajam postove, a ipak mislim da topik nije za zakljucavanje, makar za sad:)

[bolkonski]

Lako je tebi, ti ces da doguras do cina kapetana!

[Dule_smor]

bah to je nekad bilo da rezervna vojna lica napreduju maksimalno do cina kapetana...a jos ako se aktiviram, ne gine mi najmanje pukovnik!

[bolkonski]

Znam, zato ti i kazem, ali nisam znao da to vise ne vazi. Jebga. Za mene ces uvek biti najmanje kapetan!!!

[tracktorista]

dule

[peja_]

@Peja

Sto bi pogledao neko tvoje linkove kada su u odnosu na moje amaterski, pa nikom nista. Ovde nije rec o nauci nego o politici, a ja se pitam koliko su losi admini i moderatori na ovom forumu kada tema nije u najmanju ruku splitovana!

eh sad, amaterski...nemoj da pricas kojesta!

gledam sad ovu debatu sto si ti okacio (a ja nisam primetio), bas da vidim na sta lici...

inace, bole, i ti si admin ako nisi znao :D

edit: pogledao. sve sto mogu da kazem posle ove debate je da nista nisam saznao :D

70% debate pricaju o razlicitim stvarima...

neam pojma, bezveze mi je :)

[dvnityCker]

deste sta ima

kod mene nista, evo bas bio na pijaci.. u duksu.. i tako..

[brue]

The impact theory

The impact theory was beautifully simple and appealing. Much of its evidence was drawn from a thin layer of rock known as the 'KT boundary'. This layer is 65 million years old (which is around the time when the dinosaurs disappeared) and is found around the world exposed in cliffs and mines.

For supporters of the impact theory, the KT boundary layers contained two crucial clues. In 1979 scientists discovered that there were high concentrations of a rare element called iridium, which they thought could only have come from an asteroid. Right underneath the iridium was a layer of 'spherules', tiny balls of rock which seemed to have been condensed from rock which had been vapourised by a massive impact.

On the basis of the spherules and a range of other evidence, Dr Alan Hildebrand of the University of Calgary deduced that the impact must have happened in the Yucatan peninsula, at the site of a crater known as Chicxulub. Chemical analysis later confirmed that the spherules had indeed come from rocks within the crater.

The impact theory seemed to provide the complete answer. In many locations around the world, the iridium layer (evidence of an asteroid impact) sits right on top of the spherule layer (evidence that the impact was at Chicxulub). So Hildebrand and other supporters of the impact theory argued that there was one massive impact 65 million years ago, and that it was at Chicxulub. This, they concluded, must have finished off the dinosaurs by a variety of mechanisms.

Challenging the theory

But a group of scientists led by Prof Gerta Keller of Princeton and Prof Wolfgang Stinnesbeck of the University of Karlsruhe begged to differ. They uncovered a series of geological clues which suggests the truth may be far more complicated. In short, that the crater in the Yucatan is too old to have killed off the dinosaurs.

They concentrated on a series of rock formations in Mexico where the iridium layer was separated from the spherule layer by many metres of sandstone. That opinion sparked a massive row, as the supporters of the impact theory such as Prof Jan Smit of Vrije Universiteit, Amsterdam, rubbished Keller's ideas. Smit argued that the sandstone had been deposited by massive tsunami waves caused by the asteroid, and so did not undermine the idea of a single impact.

But Keller's team found evidence - such as ancient worm burrows - that suggested that the deposition of the sandstone had been interrupted many times. They concluded that there was a gap of some 300,000 years between the deposition of the spherules (from the Chicxulub crater) and the iridium (from an asteroid). Therefore there must have been two impacts.

The Chicxulub impact, they said, was too old to have finished off the dinosaurs, and there must have been another impact somewhere else which was to blame. That crater has not yet been found.

More challenges

Keller's views provoked a lively scientific row. In 2001, to try to resolve the dispute an international group of scientists extracted rock cores from deep within the Yucatan crater. Predictably, each side thought the evidence supported their argument.

Although still in the minority, Keller's work does now attract some support. And a range of scientists have begun to question other hypotheses connected with the impact theory. Claire Belcher of Royal Holloway, University of London, has found evidence which suggests that wildfires were not widespread in North America following the KT impact.

Prof Dave Archibald of San Diego State University is convinced that the survival of creatures such as frogs disproves the idea that the dinosaurs perished amid acid rain as strong as battery acid, or that an 'impact winter' caused a massive and sustained drop in temperature.

Dr Norman MacLeod of the Natural History Museum in London is among a large group of scientists who are convinced the dinosaurs were already being driven to extinction by climate change long before the arrival of the KT impact, or impacts.

[xnikolax]

kada ce ta toplota, smrzao sam se!