Extinction of dinosaurs

Yes. Of course this sort of calculations and the models which are applied here by Sagan and Toon were firstly developed for the dust storms on Mars. Low temperatures were discovered as soon as the dust started blowing. That was one point but they later applied it also for the extinction of dinosaurs. 

Meteorites also inspire fascination and concern among people. These chunks of rock fall out of the sky in apparently unpredictable patterns, often causing enormous destruction in the regions where they land. The largest meteorites to strike Earth are thought to be responsible for some of the most severe climatic changes ever to occur on the planet. Scientists now believe, for example, that the primary cause for the extinction of dinosaurs and many other species about 65 million years ago was the enormous cloud of dust produced when a meteorite struck Earth s surface. 

Some have left behind them traces of elements rare on Earth, such as iridium. The detection of traces of iridium from a large meteorite has led to a proposal that major extinction of species on Earth, namely the dinosaurs, could be due to the meteorite impact, causing chemical, light and temperature fluctuations, i.e. global climate changes, though this proposal is not universally accepted. 

Figure 1.6 Impact frustration (a) the Chicxulub crater, seen as a three-dimensional gravity map, thought to be responsible for the extinction of the dinosaurs (b) the cratered surface of the Moon. (Reproduced from photos by courtesy of NASA)...

Impact frustration A process typified by the extinction of the dinosaurs where the Earth s surface may have been sterilised of all life forms by the impact of a large meteorite or comet... 

Impact frustration The collision of a large meteorite with a planet that results in the extinction of some or all species on the planet, causing the sterilisation of life. An example would be the extinction of the dinosaurs. 

We were not able to determine exactly the length of time associated with the deposition of the clay layer. Instead the laboratory studies on the chemical and physical nature of the Cretaceous-Tertiary boundary led to the theory that an asteroid collision with the earth was responsible for the extinction of many forms of life including the dinosaurs. 

The extinction of the dinosaurs had one enduring consequence for us mammals we took over as important players among the living organisms on Earth. While the dinosaurs reigned, the mammals were bit players on the stage of life. If dinosaurs had survived, mammals might have continued to be of minor importance on Earth. 

An interesting story as to how most of the iridium appeared on Earth was explained recently by scientists who discovered a thin layer of iridium in the sediments that were laid down in the Earth s crust at the end of the Cretaceous period. This was a period about 65 million years ago when meteors and asteroids crashed into the Earth. These extraterrestrial bodies contained a high percentage of iridium. Dust from the impact spread around the Earth and blocked the sun for months, resulting in the extinction of many plants and animals, including the dinosaurs. This extensive dust cloud also deposited a thin coat of the element iridium that was contained in the fiery bolides. 

Ir anomalies. Currently, scientists are attempting to establish the order ol mass extinctions. Present opinions seem to suggest that the extinction of terrestrial lanna. including the dinosaurs, teas an csent that followed rather than occurring concurrently with the catastrophe met by many murine species. Sec also Chemical Elements, and Platinum and Platinum Group. 

Cenozoic Era A geologic time span that ranges from the extinction of the dinosaurs about 65 million years ago to the present. 

The last globally catastrophic collision between Earth and an asteroid probably took place 65 million years ago at the end of the Cretaceous period. It now seems reasonably likely that the extinction of many species, including the great dinosaur extinction which occurred at the Cretaceous-Tertiary boundary, was caused by the impact of an asteroid approximately 6.2 mi (10 km) in diameter. The submerged remnants of the giant impact crater produced in this terminal Cretaceous collision were recently discovered on the coast of the Yucatan peninsula in Mexico. The crater, Chixulub (pronounced CHIKS-a-lub), is approximately 112 mi (180 km) in diameter and has long been buried under coastal sediments. 

Iridium may be a key element in the puzzle of dinosaur extinction. Scientists search for iridium in the soil to track the impact that a giant meteor had on Earth 65 million years ago. 

Cretaceous 138 Ma Most continents widely separated continued radiation of dinosaurs angiosperms and mammals begin diversification mass extinction at end of period... 

Figure 1 Geological timeline from the formation of the Earth 4.6 billion years ago to the present day. Note the immense duration of the Precambiian era. The first plants and animals appeared around the time of the Cambrian explosion 543 million years ago. The extinction of the dinosaurs was about 65 million years ago.

Uncle Donald may believe something that we do not — that pterosaurs, sometimes considered the sister group of dinosaurs and birds (Dingus and Rowe, 1998 160), are paraphyletic. Or he may regard as ancestral an extinct sister group, whether it be paraphyletic or not. That it be extinct and related is enough for a judgement that accepts, as evidence of ancestry, an interpretation of that kind. 

How does the study of dinosaur extinction illustrate the scientific method ... 

In your opinion, is it justifiable to refer to the asteroid explanation as the theory of dinosaur extinction ... 

Major catastrophes that lead to mass extinction of species occurred five times in Earth s history during the last 540 million years the last one was 65 million years back (end of the Mesozoic) when the dinosaurs disappeared. The high rate at which species are disappearing has led scientists to suggest that the sixth mass extinction is already under way Barnosky estimates that in 330years, 75% of mammalian species will be extinct (Barnosky et al., 2011). 

Analysis of rock specimens by NAA is helpftil to geochemists in research on the processes involved in the formation of different rocks through the analysis of the rare earth elements and other trace elements. For example, the discovery of anomalously high iridium concentrations in 65-miIlion-year old limestone deposits from Italy and Demnark have been accomphshed by NAA. The NAA findings support the theory that extinction of the dinosaurs occurred soon after the impact of a large meteorite with the earth. The study of low concentration of U in stony and meteorites and trace elements in Apollo-II lunar rocks (Ganapathy et al. 1970) have been imdertaken through NAA. Detection... 

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