Physical Geology Essay Assignment: Mass Extinctions
Topic: The Cretaceous - Tertiary extinction
ID No. 15240
UNIVERSITI TEKNOLOGI PETRONAS
The Cretaceous-Tertiary extinction
Fastovsky, D.E. and Weishampel, D.B., 2005 defined the mass extinction “Mass extinctions involve large numbers of species and many types of species undergoing global extinction in a geologically short period of time”, organisms have gone extinct, certainly the present day living things is not the same as in the past. The world has changed over time, leads the existing change and some of them were extinct. In 1983 two paleobiologists, D. M. Raup and J.J. Sepkoski, University of Chicago recognized 15 intervals of mass extinction and divided into three big mass extinctions which are minor, intermediate and major mass extinction. They concluded that the major mass extinction is the only one which is called Permo-Triassic extinction. The dinosaur extinctions were classified as intermediate mass extinctions. Raup and Sepkoski (1982) said in more scientific the mass extinction refers to a large number of different types of organism occupying a range of diverse and widespread environment, with the rate of disappearance of species largely exceeding the natural extinction rate determined from the fossil record. The causes of the extinction are numerous, scientists often differ on the possible causes’ different extinction phenomenon.
Prothero, D.R. (2004) stated that the extinction to which the dinosaurs finally vanished is called the Cretaceous-Tertiary extinction at the end of Mesozoic Era, which commonly abbreviated K/T extinction. Indeed, the K/T extinctions wipe out not only the dinosaurs but also the ammonites, the marine reptiles, plankton and many others marine invertebrates.
2. The main possible causes for the K/T mass extinction
2.1 Volcanic eruptions
Fastovsky, D.E. and Weishampel, D.B. (2005) said some geologist have assumed that during the time of Late Cretaceous, the giant volumes of volatile gases includes carbon dioxide, sulfur oxide and nitric oxide were emitted into the atmosphere by the interval of volcanisms with generally increased the explosion, affecting the global temperatures and destroying the ozone layer led to the producing the greenhouse effect. Some were produced acid rain caused by acid chemical substances polluted in the atmosphere. Those are the phenomenon that causes the extinction of inhabitants. “Most of the impact scenarios postulate a long period of cold and darkness caused by the cloud of impact debris and dust, and some also suggest global wildfires and acid rain as well” (Prothero, D.R., 2004)
2.2 Reduction of oceanic level
The gradually lowering of the sea level since the time before the Cretaceous until the Cretaceous time (around 65 million years ago) resulted of many continental land mass were exposed during the Cretaceous time and it was affected in the extinction of animals and plants both marine and terrestrial. Some of the marine vertebrates during the Cretaceous time were plesiosaurs, ichthyosaurs and mosasaurs. Moreover University of Washington paleontologist P.D. Ward concluded that the invertebrates lived in the time were ammonites and some of bivalves. (Fastovsky, D.E. & Weishampel, D.B., 2005)
Figure 1: Some of the better known inhabitants of cretaceous sea. Vertebrate are: (a) ichthyosaur, (b) mosasaur and (c) plesiosaur. The shelled are cephalopod mollusks called ammonites (d).
2.3 Climate change
Fastovsky, D.E. and Weishampel, D.B. (2005) explained Wolfe J.A., a paleobotanist concluded from the U.S Geological Survey that the normal temperature range during the Cretaceous time was 8 degree Celsius which is taught that the dinosaurs can lived within the temperature between 2 and 8 degree Celsius. In the same region, in the North America, the temperature tends to be increased until the current...
Bibliography: Alvarez, L.W., Alvarez, W., Asaro, F. & Michel, H.V. (1980, June 6). Extraterrestrial Cause for the Cretaceous-Tertiary Extinction. Science, 208(4448), 1095-1108.
Cowen, R. (2003, April 4). Welcome to geology 107, Winter 2003. The Cretaceous-Tertiary Extinction. Retrieved 9 April 2012 from http://mygeologypage.ucdavis.edu/cowen/~GEL107/index.html
Erwin, D.H. (1996, July). The Mother of Mass Extinctions. Scientific American.
Fastovsky, D.E. & Weishampel, D.B. (2005). The Evolution and Extinction of the DINOSAURS (2nd ed.). The Cretaceous-Tertiary extinction: the frill is gone Geological record of the latest Cretaceous. New York: Cambridge University Press.
Nichols, D.E. & Johnson, K.R. (2008). Plants and the K-T Boundary.
New York: Cambridge University Press.
Prothero, D.R. (2004). Bringing FOSSILS to life: An introduction to Paleobiology (2nd ed.). Extinction. New York: McGraw-Hill.
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