Reference no: EM133347642
Case Study: San Francisco (UPI) - A team of scientists is proposing that dinosaurs were wiped out 65 million years ago by a spectacular collision of Earth with an asteroid that cast the globe into several years of dust-choked semi-darkness. This new hypothesis would explain why 75 percent of all living species disappeared at the same time. The idea was advanced Friday at the annual meeting of the American Association for the Advancement of Science.
The most common explanation for the global catastrophe has been that water retreating from the continental shelves caused climatic changes to which the dinosaurs could not adjust. A recent theory suggests that the climatic changes were caused by a massive invasion into the oceans of fresh water from the Arctic Basin.
But Dale A. Russell, a Canadian paleontologist, told a symposium that no physical evidence exists to support the notion of sharp temperature declines. The new hypothesis was explained by Luis W. Alvarez, a Nobel laureate physicist at the University of California. His team has been pondering mysterious deposits of a rare element, iridium, at sites in Denmark, Italy and Spain.
The iridium was laid down in limestone at the exact time of the dinosaurs' demise, and the iridium concentration was 160 times what might have been expected. Iridium is a thousand times more abundant in meteorites than in the Earth's crust, a fact that suggests that the deposits came from an extraterrestrial source.
Alvarez proposed that Earth was struck by an asteroid six miles in diameter that blasted a crater 100 miles wide with the force of 100 million hydrogen bombs. Such an explosion would have thrown an enormous quantity of dust into the stratosphere where, according to the hypothesis, it remained for several years casting Earth into semi-darkness. Lack of sunlight would have killed plankton in the ocean and plants on land, thus depriving fish and animals of food.
Russell concluded from evidence in fossils that 75 percent of all living species, including the dinosaurs, the most intelligent creatures of the time, became extinct.
Questions:
a.) Assuming that the Implicit Question for this argument is "How did the dinosaurs (and others) become extinct?" Schematize the argument for Alvarez's conclusion. Make sure you Mark all Trace Data as TD.
b.) State a Rival Conclusion that is explicitly mentioned in the article (call it C2).
c.) State another rival (your own C3) that is compatible with the support claims.
d.) What is the plausibility ranking of these three rivals (rank the rivals vertically from most to least likely)?
e.) Provide some new evidence that would clearly change the ranking (make one of the other rivals the most likely one).