Did asteroids kill the dinosaurs - Coursework Example

Many scientists currently believe that a large asteroid impact caused such devastation on the planet that nearly all of the higher life forms, including the large dinosaurs, were killed off. This is evidenced by a large crater found outside of Chicxulub, Mexico, which is also known as the Yucatan crater because it is found at the end of the Yucatan peninsula. At first, however, the main source of evidence for this theory was the existence of a layer of irridium dust found in many places all over the planet.

This element is not commonly found in large amounts on the Earth's surface, and its presence in a single band at a similar depth in a number of different soils could mean that a large asteroid containing irridium crashed into the Earth and scattered dust all over the planet (York 2006). When the Chicxulub crater was eventually found, it turned out to be an elongated crater from a hit that most likely involved a low angle of impact. This further supports the irridium evidence since the low angle of impact means that the asteroid would have basically exploded, sending its pieces flying, as well as throwing up a huge cloud of dust and debris (Hecht 1996).

The asteroid theory states that the dinosaurs would have been killed as a result of this dust cloud. The dust cloud was so enormous as to have risen into the atmosphere and been swept around the planet by the circulating air currents. The sunlight would be blocked out by this dust cloud, reducing the ability of plants to photosynthesise and create energy off of which they could live. Since plants are at the bottom of nearly all of the food chains on Earth, without the energy provided to them through photosynthesis, animal life struggled to find enough food.

Most of the dinosaur species were large and heavy, requiring huge amounts of plant life to support their energy needs; as the plants died out, so did the dinosaurs, leaving only the relatively much smaller mammals and birds. In addition, this cloud caused the temperature all over the planet to drop, directly killing off many dinosaur species (York 2006). However, no actual physical evidence exists that the asteroid which struck at Chicxulub was responsible for those changes. The fossil record of that era is scarce, and some of what does exist suggests a much longer and drawn-out extinction event than is usually suggested with the asteroid extinction theory.

This claim, though, is based on studies performed in the Far East, especially China, which is far from the suggested impact site. Perhaps the fossil record at this location suggests a slower extinction because it is far from the impact crater and so the climate changes and plant life die-off happened slower (Zhao et al. 2008). Climate change is another suggestion for what could have killed off the dinosaurs. Most dinosaurs were what is known as ecothermic reptiles, taking in their heat from the environment rather than making it themsevles as mammals and birds do.

In addition to the direct effects of the temperature dropping, the climate change would also have affected plant life in the same way that climate change after the asteroid would have. However, the ultimate cause of this climate change, other than if it were caused by the