Ordovician-Silurian mass extinction is one of the greatest mass extinction in the history. According to statistics, over one hundred families became extinct. This was associated with the movement and fragmentation of the supercontinent. Secondly was as a result of ocean cooling beyond levels the organisms could survive. While the organisms had initially adapted to the warm tropical conditions, the sudden transition to the cold climate was unbearable for most organisms (“Ordovician”,n.d.)..
The late Devonian mass extinction is thought to have been warm and dry period. It was characterized by Devonian fish that was the main components of marine life and the chief predators. However, the attributed cause of end-of-period extinction is the development of the glacial condition in the South Polar Region and unexpected cooling of the oceans as a result of glaciation (Sepkoski, 2001).
Permian mass extinction is alleged to have occurred during in about 248 million years ago. It resulted from the formation of a super-continent whose area exceeded that of the ocean. As a result, there was a broad diversification of terrestrial vertebrates and a devastating reduction of marine community. Amphibians, insects as well as reptiles were among those affected (“The Permian Mass Extinction,” n.d.).
Triassic-Jurassic mass extinction is regarded as the minor extinctions in the geological history. However, they are critical to the understanding of the extinction patterns. The Triassic extinction is said to have been caused by extra-terrestrial influences, cooling of the global climate or bursts. Although it adversely affected mammal-like reptiles, molluscs, thecodonts and gastropods, it gave time to the dinosaurs acclimatize in terrestrial edges that were then unavailable. The Jurassic was more severe as it caused the extinction of over eighty percent of marine species. Unlike the Triassic period, this negatively affected the dinosaurs.
Cretaceous-Tertiary mass extinction occurred in the period about 144 to 65 million years ago as a result of numerous radiations. At the end of the radiations, a massive extinction occurred where an approximated 85 percent of the species lost their life. This was the second largest historical mass extinction. It is renowned as the cause of the end of dinosaurs. However, other marine and terrestrial groups were also rigorously affected. Such include the likes of ferns, pterosaurs, marine reptiles and ammonoids among others (Alvarez et a., 1980). Other organisms like diatoms, molluscs and dinoflagellates also became extinct in this extinction. The primary causative agent is assessed to be impacts of meteorites and comet showers. However, other hypothesis alleges geographical mechanisms like vulcanization as the cause (“Causes of the Cretaceous Extinction,” n.d.).
2) The end of the Paleozoic & Mesozoic Eras is characterized by the extinction of dinosaurs and large populations of reptiles. Also, it marked the end of tropical forests both occurrences that have not replicated since then. The end of the Paleozoic era proceeded the Permian period when there was more than ninety-five percent mass executions (“The Mesozoic Era,” n.d)
3) Asteroid Holocaust Theory was invented by Water Alvarez, a then geologist, who looked forward to quantifying faunal variations around the KT boundary. He reasoned that for the rate to be effectively quantified then, timekeeper was vital. The theory alleges that Ir-enriched layer resulted from the impact of vast asteroids that provide large masses of dust in the atmosphere to cool the globe for more years. The theory help shuts down photosynthesis hence leading to the collapse of the overall food chain. Up to now, theories state the asteroid holocaust theory as the leading in the description of the gradual extinction in globe over millions of years (“Solar System Fluff,” n.d.).
4) The Oort cloud and Kuiper belt are both the leftovers of the nebula out of which the solar system originated from. Their distribution and composition place vital limitations on solar system evolution models. The Tunguska event was a blast that occurred in 1908 as a result of seismic waves. Asteroids plunged into the earth’s atmosphere at a rate of 33,500 miles per hour caused devastating pressure and heat over the land. The event occurred in Russia. The possibility of a similar event taking place is unpredictable. Scientists all over the world have not been able to determine when a meteor can be dislodged (“The Kuiper BeltandThe Oort Cloud,” n.d.).
5) When an asteroid hits the land, a huge amount of dust would be produced hence dusting the atmosphere. On the other hand, if it hits the water, there would be an increase in water vapor in the atmosphere. As a result, rain would increase and hence mud and landslides. Hurricanes, earthquakes or tsunamis may eventually increase from the rise in kinetic energy. The impact also produces nitrous and nitric acids that may occur in the form of acid rain. The craters would depend on the size of the asteroid and the size or depth of water body struck.
6) Pleistocene Extinction refers to the event that led to the elimination of mammals weighing 40 kg and above at around 10,000 BP. It is alleged that the animals died from either climate change, extermination by humans usually referred to as overkill hypothesis or catastrophes like fire. Overkill hypothesis is an assumption that humans hunted and killed most of the animals during the Pleistocene extinction (“The Late Pleistocene Extinctions,” n.d.).
7) Scientists have asserted that the sixth mass extinction will wipe out all organisms. The extinction will result from the change in the ecological system. If the Homo sapiens become extinct, 50M years from now, the world will be covered with natural forests full of clean streams. This is because humans are always clearing forests for cultivation, settlement and industries. The same industries have caused massive destruction to the environment and led to drastic climate change. Our closest relatives the chimpanzees are likely to replace us though they may not evolve the human level of intelligence (“Humans won't survive next mass extinction”, n.d)
References
1908 SIBERIA EXPLOSION: Reconstructing an Asteroid Impact from Eyewitness Accounts. (n.d.). Retrieved March 29, 2016, from https://www.psi.edu/epo/siberia/siberia.html
Alvarez, L. W., Alvarez, W., Asaro, F., & Michel, H. V. (1980). Extraterrestrial Cause for the Cretaceous-Tertiary Extinction. Science, 208(4448), 1095-1108.
Causes of the Cretaceous Extinction. (n.d.). Retrieved March 29, 2016, from http://park.org/Canada/Museum/extinction/cretcause.html
Humans won't survive next mass extinction – scientists. (n.d.). Retrieved March 29, 2016, from https://www.rt.com/uk/312455-human-beings-mass-extinction/
Ordovician. (n.d.). Retrieved March 29, 2016, from http://earth.usc.edu/~stott/Catalina /Ordovician.html
Sepkoski, J. (2001). Mass Extinctions, Concept of. Encyclopedia of Biodiversity, 97-110.
Solar System Fluff. (n.d.). Retrieved March 29, 2016, from http://www.astronomynotes. com/ solfluf/s5.htm
The Cretaceous Extinction. (n.d.). Retrieved March 29, 2016, from http://hannover.park.org/ Canada/Museum/extinction/cretmass.html
The Kuiper BeltandThe Oort Cloud. (n.d.). Retrieved March 29, 2016, from http://nineplanets.org/kboc.html
The Late Pleistocene Extinctions. (n.d.). Retrieved March 29, 2016, from http://exhibits.museum.state.il.us/exhibits/larson/lp_extinction.html
The Mesozoic Era: Age of Dinosaurs. (n.d.). Retrieved March 29, 2016, from http://www.fossils-facts-and-finds.com/mesozoic_era.html
The Paleozoic Era: Life In The Water. (n.d.). Retrieved March 29, 2016, from http://www.fossils -facts-and-finds.com/paleozoic_era.html
The Permian Mass Extinction. (n.d.). Retrieved March 29, 2016, from http://park.org/Canada /Museum/extinction/permass.html
