Introduction When looking at any mass extinction event, there are a number of questions that will invariably need to be answered. When did it happen? How many species were affected? Which ones were they? What was the cause of such widespread death? How did some species survive while other, thriving ones were wiped out completely? For four of the “Big Five” mass extinction events, the Ordovician-Silurian, Permian, Triassic-Jurassic, and Cretaceous-Paleogene, the answers to these questions are all agreed upon, almost universally. The remaining event, known as the Late Devonian mass extinction, lacks a definitive answer as to the cause. Understanding the cause of extinctions, especially ones of such magnitude as the Big Five is incredibly important. …show more content…
It is known that this event marks the boundary between the Frasnian and Famennian ages. Beyond that, little is known with certainty. Not even the dates that it took place during are completely agreed upon. Recent radioactive dating indicates that it most likely happened around 376 million years ago (Racki, 2005, p. 11), though that date can vary by up to two million years, as is shown in the figure. This lack of a definitive date makes connecting short term and sudden events, such as an asteroid impact or volcanic eruption, nearly impossible to link to the event. What is mostly agreed upon, though, is that the Devonian extinction “event” was actually a series of smaller events that took place over the span of about a million years (McGhee Jr, 2005, p. 40). During this time, reef-builders, such as stromatoporoids and corals, were affected greatly. Many brachiopods, trilobites, and fish were also heavily impacted. In all, about 70% of invertebrate species were extinct by the end of this event, almost all of which lived in marine environments (House 2009). Land animals were left more or less unphased by this event that eliminated so many aquatic …show more content…
First of all, there must be some supporting evidence of the purported cause. Without it, a hypothesis can be quickly ruled out as a possibility; it can’t have caused such widespread deaths if there’s no proof it ever happened. The claim must also account for which species went extinct. Within that comes justification for why some species went essentially unaffected. The distribution of extinctions must also be supported, such as why some environments and locations appear to have been hit harder than others. In the case of the Late Devonian mass extinction, it would have to provide reason for why it was almost exclusively marine invertebrates that
The possibility if a meteor strike as the cause of extinctions is discarded, something that most specialists agree on. There is no evidence of any meteor crater big enough or recent enough to be accountable for it; there are no “elements that are common extraterrestrially but less so on Earth, such as iridium, and no sign of a tsunami or other phenomena following the impact.” The extinctions where also very selective and occurred over a very long period of time. If a “one shot” catastrophe had been the cause it would have affected all species at the same time and in similar
The question of what caused the extinction of megafauna during the Late Pleistocene period is one that archaeologists have struggled to answer for decades, but why should it matter? Discovering with certainty the cause of megafaunal extinction would simultaneously prove or disprove any of the proposed implications of each existing theory regarding this massive extinction.
On May 22, 1915, an explosive eruption at Lassen Peak devastated nearby areas and rained volcanic ash farther 200 miles to the east! This explosion was the most powerful in a series of eruptions from 1914 through 1917. ...
The Permian Triassic extinction was an event of cataclysmic disaster and almost the extinction of all species on planet earth. The Permian Triassic extinction is said to have occurred millions of years ago, geologist have estimated that its occurrences happened about 248 million to 286 million years ago. This rare occurrence of events proceeded the Triassic geologic periods and the Paleozoic and Mesozoic eras. This mass disaster was the largest dissipation of living life on planet earth; it is believed to be even superior to other crises such as the Ordovician and Devonian events and the conclusion of the cretaceous era that came upon the dinosaurs.
The Permian Period occurred around 298 million years ago. It stretched from the Carboniferous Era to the Triassic. Sir Roderick Murchison in the early 1800’s noticed a differentiation among the overlay of the rock formation in the Ural Mountains in Russia. These rocks differed from the older Carboniferous rocks in Britain, and seemed younger than the Triassic rocks of Europe. Murchison named this differentiation after the prehistoric kingdom of Perm, thus the Permian Period.
Long-term survival of a species depends on its ability to adapt to changing environmental conditions (Murphy, 1994). Genetic diversity within a species, which has taken 3.5 billion years to evolve, makes adaptations to these changing environments possible. Unfortunately, the rate of extinction of genetically diverse organisms is rapidly increasing, thus reducing this needed biodiversity, largely due to the human impacts of development and expansion. What was an average of one extinction per year before is now one extinction per hour and extinct species numbers are expected to reach approximately one million by the year 2000 (WWW site, Bio 65). As a result governmental and societal action must be taken immediately!
Sex, drugs, and disasters are both popular topics that grab public attention and scientific theories of the extinction of dinosaurs. While sex and drug hypotheses represent silly speculations, the disaster claim is good science: it provides testable evidence, has an impact on other scientific fields, and generates continuous research.
...asted about a million years. The eruption was not violent compared to others, but it was able to send ash as high as the stratosphere. So another theory is that shifting of the tectonic plates caused the Deccan Traps to erupt, causing the release of massive amounts of carbon dioxide out of the earths crust. This went on to create a global greenhouse effect that cooked the planet. This along with climate change from continental drift could have caused the K-T event. Paleontologist Richard Cowen believes the evidence of an asteroid impact is so strong that there is no point to explain that evidence as solely volcanic effects. We should concentrate on the fact that the K-T boundary coincided with two different, yet very dramatic events.
Several mass extinctions have occurred during the Earth’s history. The Cretaceous – Tertiary Boundary (K-T) Extinction caused the loss of at least three-quarters of all species known at that time including the dinosaurs. The cause of this mass extinction is a controversial subject among scientists but the fossil evidence of it’s occurrence is abundant.
The Permian Period commenced 298.9 million years ago and ended 252.2 million years ago, ranging from the close of the Carboniferous Period and the beginning of Triassic Period. About 250 million years ago, at the end of the Permian period, something killed some 90 percent of the planet's species. The species of animals in the seas survived no more than 5 percent. On land less than a third of the large animal species made it; nearly all the trees died (Hillel J. Hoffman, 2015). Marine life was devastated, with a 57% reduction in the number of families (Sepkoski, 1986). Oceanic life suffered the most, but terrestrial life forms were also greatly affected. All major groups of oceanic organisms were affected with the crinozoans (98%), anthozoans (96%), brachiopods (80%) and bryozoans (79%) suffering the greatest extinction (McKinney, 1987). The world, today, is alive because of the remaining 10 percent. The events that took place were in phases and some of the causes were an asteroid hitting the earth, sea level fluctuations flood basalt eruptions, a drop in oxygen levels from the acid rain caused by volcanic ash, calamitous methane release, etc.
In the early nineteen hundreds, dinosaur fossils were discovered and recognized around the globe. Greedy scientists and civilians, searching for their own prize skeleton, rushed to rip bones out of the ground, destroying the fossils as they went. It was not until later in the century that scientists and paleontologists began pondering how such widespread creatures disappeared. Currently, paleontologists debate the two main hypotheses of how the classic dinosaurs died: from volcanic activity or an asteroid impact. Although they result in the same outcome, the volcanic and asteroid hypotheses differ in key elements: the actual event, the environment's stress, and the impact on life.
Earth has gone through five fully major extinctions before. We currently are in the process of Earth’s sixth mass extinction. This mass extinction is closely related in severity to the extinction of the dinosaurs. Earth’s extinctions are broken into three different areas. The first area was the large number of animals caught by hunter-gathers. The discovery of agriculture led to the second area of extinction, wildlife habitats. These wildlife habitats were destroyed due to humans starting to stay in one area.
The prominent theory is that dinosaurs died in a fiery death due to an asteroid crash on Earth, but is that really what caused their mass extinction? Every scientist has a theory, and with so many out there it was hard to just pick one, they all made sense. It is completely possible for a volcano to have killed the dinosaurs, or even an asteroid. Another popular theory was the ice age. These were all plausible reasons for the extinction of dinosaurs, and that’s when the combination theory was discovered. It is a theory that states there were several factors that played into the extinction of the dinosaurs. The dinosaurs died due to the environmental factors that are included in the combined theory.
Almost 23% of all families, 48% of all genera (20% of marine families and 55% of marine genera) and 70% to 75% of all species went extinct (Beaz). Although the cause of this mass extinction is debatable, many speculate that global warming was the killer. Because Pangea was breaking up into Laurasia and Gondwanaland, there was widespread volcanic activity caused by the rifting, increasing atmospheric carbon dioxide. The massive release of this greenhouse gas increased global air temperatures and resulted in acidified oceans along with rising sea levels. If this is the case, the life in the ocean would have died at a significant rate. Many families of brachiopods, gastropods, bivalves, and marine reptiles became extinct (Rafferty). An important trace fossil known as the phylloceratid ammonoid was able to survive, and they gave rise to the explosive radiation of cephalopods later in the Jurassic Period, as well as evolved into many different forms during the later Cretaceous (End Triassic Extinction). This extinction event ranks fourth in severity of the five major extinction events over geologic history