There are several theories that have attempted to explained the extinction of dinosaurs in the past and at the present. However, three of the theories have been consistent: asteroid impact theory, marine regression and habitat regression, and massive eruptions of flood basalt. Analysis of these three theories showed that they are mutually exclusive and they range from very short to very long-term in both duration and effect (Elewa, 2012). The asteroid impact theory is the most catastrophic of all the three theories and it argues that asteroid of 10-km (6-mi) struck the earth ejecting a plume that reaches the atmosphere and blocked the rays of the sun from reaching the earth surface. As a result, the photosynthesis process was curtailed leading to the death of many plant and herbivores and subsequently the carnivores.
The second theory is marine regression and habitat fragmentation that have taken place over a longer interval of time probably from tens to hundreds of thousands of years. In this case the marine regression is described as a process of draining of epicontinental seas (Archibald, 2012). The theory estimated that during this period 29 million square km (11.2 million square mi) of land were exposed. This led to the extinction of marine life including the dinosaurs.
The third theory is the massive eruption of flood basalt, which occurred in the Indian subcontinent over an extended period of time as compared to marine regression. The theory approximate that the volume of the material that erupted during this period was enough to cover both Alaska and Texas to a depth of 610 m (200 ft) (Archibald, 2012). The cause of massive eruptions have not been studied well, but many research have relate these events with volcanism.
Currently, there are two scientific methodology that is used to explained the extinction of dinosaurs: The ‘Gradualist’ Model and the ‘Catastrophist’ Models. The gradualist model relies on the gradual ecosystem evolution model with the assumption that as the number of mammals increases, the number of dinosaurs declined until they disappear altogether (Elewa, 2012). It involves the analysis of the fossil records and ecological events to establish the changes in the existence of the species. On the other hand, the catastrophist model relies on the extraterrestrial scenarios that causes huge impact on the earth surface. It involves the analysis of certain elements that are associated with comet such as the isotopic changes in C and O and presences of chondrites. It has been also explained through the analysis of abrupt shift in pollen ratios.
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