The Late Devonian Mass Extinction Period

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The cause of the Late Devonian mass extinction near the Frasnian-Famennian boundary remains uncertain. Anomalies of stable isotope values have been observed at the Frasnian-Famennian boundary commonly, indicating the abrupt changes of environments during the crisis. These changes include marine anoxia possibly triggered by land plant evolutions, global cooling, and global warming probably induced by multiple bolide impacts. In this study, the variations of isotope compositions are summarized to investigate the possible major causes of F-F mass extinction.

Assess the different hypotheses put forward for the mass extinctions at the end of the Permian and Cretaceous (KT) Periods.

<b>Introduction</b><br>Think of a world which existed 290 million years ago. As you look out over the terane in front of you, you think that you are on an alien planet. You see volcanoes spewing ash and lava. Beside them is the ocean which is swarming with many different species of echinoderms, bryozoans and brachiopods. As you look down onto the sea floor you are amazed at the countless number of starfish and urchins. Some animals leave you can't even describe and you have no idea even what phylum they belong to. This is a world at its height in diversity of oceanic species. Millions of wonderous species existed at this time in the ocean and most of them will never appear again in earth's history. In the geologic time scale, a million

The cretaceous-tertiary (KT) boundary extinction happened approximately sixty five million years ago. Sixty to eighty percent of all living species became extinct at this boundary (Raup 1988). The KT extinction was indeed a mass extinction event. Mass extinctions are periods in Earth's history when extremely large numbers of species die out simultaneously or within a limited time frame. The most severe mass extinction ever occurred at the end of the Permian period when 96% of all species died out. The K-T mass extinction obliterated almost all the large vertebrates on Earth, on land, at sea, and in the air (all dinosaurs, plesiosaurs, mosasaurs, and pterosaurs) suddenly became extinct at the end of the Cretaceous Period. At the same time, most

The dinosaurs appeared after the greatest mass extinction event occurred. This is known as the Permian-Triassic extinction. It has been estimated to have occurred around two hundred and fifty million years ago. (6) It is also known as the Great Dying with over ninety percent of species dying off, leaving the Earth essentially a wasteland. It led to the extinction of “57% of all families, 83% of all genera and 90% to 96% of all species. 53% of marine families, 84% of marine genera, about 96% of all marine species and an estimated 70% of land species, including insects.”(7) By the late-Permian, global temperatures were very hot, with them being the highest ever on the planet.

The initial stage was thought to have been a deadly drop in sea level that led to a loss of habitat stability. The second stage would possibly have been the volcanic eruptions and the release of carbon dioxide into the air causing oxygen levels to decrease. The final stage would possibly have been the rise of the sea levels causing massive floods and destroying near shore habitats. Having all of these three stages at one time would have caused this massive kind of extinction. However, if only one of these stages had happened this extinction would not have been nearly this massive. Studies show that even though this mass extinction may have seemed like a fast-moving process, it took over a million years to

Since the 1980s the most popular theory for why dinosaurs became extinct was because of a meteor, but many people are skeptical of whether or not the meteor was the only factor in the extinction of the dinosaurs. In Stephen Brusatte’s “What Killed the Dinosaurs,” Dr. Brusatte talks about how the mystery of the extinction of the dinosaurs was a hug influence on his life and caused him to become what he is today. As a teenager Brusatte had a chance to talk to Walter Alvarez, the man who proposed the idea of a meteor being the cause for the extinction of the dinosaurs. Alvarez was able to come up with this hypothesis by examining the clay band between the Cretaceous period and the Paleogene period. The Cretaceous period was a time when the Earth had a surplus amount of dinosaurs and the Paleogene period was the time period directly after the Cretaceous period where dinosaurs had become extinct. When Alvarez studied the clay band he had discovered that the band was saturated in iridium which is an element common on meteors and asteroids. This led him to believe that a meteor may have led to the downfall of the dinosaurs.

The Devonian period initiating approximately 416 Mya and culminating 359 Mya represents a geologic time period, which characterizes a major part of the Paleozoic Era. Traversing between the Silurian period (444 - 416 Mya), and Carboniferous period (359 – 299 Mya) the Devonian period epitomizes substantial modifications in the world's ecology and geography.

The Frasnian-Famennian mass extinction in the Late Devonian has often been considered as one of the major 5 extinctions through time. Conflicting interpretations for the cause of this extinction exist, but the role of volcanism is becoming increasingly appealing due to recent advances in radioisotope dating. New K-Ar and 40Ar/39Ar ages for the Viluy traps in Siberia suggest multiphase emplacement of the Viluy traps with an early phase likely contributing to the Frasnian-Famennian mass extinction. Other work supports this idea of multiphase emplacement. Changes in earth systems during the late Devonian support the argument for the role of volcanism as a root in the destruction of multiple marine habitats during the Late Devonian. One explanation for the Frasnian-Famennian extinction involves an initial pulse of Viluy Trap volcanism which lead to elevated levels in the atmosphere, marine anoxia and ultimately extinction.

“A minority disputes this theory, arguing that other events-such as volcanic eruptions, sea-level changes or a series of impacts-were to blame for the spectacular loss of species that occurred at the transition between the Cretaceous and Tertiary periods…”

Throughout a lifetime the things that make us, as individuals, feel joy give meaning to our lives, without these things we have no meaning to be on Earth. Hemingway takes the reader on a journey of adding meaning to life. He shows the reader that the soldiers feel nothing towards the war and it is just something to do. Frederick Henry, a soldier, gives up on the war and decides to no longer be apart of something he does not care for. When Henry meets Catherine Barkley, she does not affect his existence until later in the novel. He lies to her and does not realize how important their time spent together truly is. Eventually, Henry realizes he does love Catherine. She changes his life for the better and when he is not around her he feels empty. His entire existence revolves around her. At the end of the novel, Henry gets the meaning of his life stripped away from him when Catherine dies after childbirth and he no longer feels any sort of emotion. In A Farewell to Arms, Ernest Hemingway explores through detail, setting, characterization, symbolism, and imagery that life is a useless, blank canvas until it is painted to evoke meaning and demonstrate a story.

Gerta Keller, professor of geosciences at Princeton University, has recently conducted research on the Chicxulub asteroid in which she analyzed new core samples taken from the asteroid site (Botzer 2004). These samples indicate that the impact that occurred at Chicxulub actually predated the mass extinction of the dinosaurs, which occurred at the Cretaceous-Tertiary boundary about sixty-five million years ago. Keller claims that the Chicxulub impact occurred approximately 300,000 years before the extinction (Keller 2004). Although previous researchers estimated that the Chicxulub asteroid was the cause of the extinctions, there had always been doubts about the exact age and size of the crater, and about the origin of the “mega tsunami deposits” that were located within the crater (Keller 2004). The focus of Keller’s recent research was on finding some answers to these questions. To do so she analyzed Cretaceous limestone, dolomite, and anhydrite deposits as the site of the Chicxulub crater (Keller 2004).

The asteroid theory is a theory that has an outstanding amount of evidence backing it up. Experts in geology, palaeontology and other related fields (Yarris, 2010) believe that this theory is highly likely to of caused this enormous mass extinction. Evidence proves that an asteroid hit Earth around sixty-five million years ago and is believed to have had a diameter of approximately 6-15km. This is the same time period as when the dinosaurs were alive, so this massive asteroid would of put a lot of pressure on the earth and could of been the reason why we no longer have dinosaurs roaming our earth. This asteroid hit earth with the force of five billion atomic bombs and destroyed everything in its path, causing fires, earthquakes, tsunamis, and put dust, debris and

The debate over what happened to the dinosaurs have been one of the most controversial research topics in history. One minute, the earth was blooming with countless trees and a healthy environment, then, in the period of seconds, all life on earth was wiped out, creating a mass extinction across the globe (Bond, 2017). Discovering what ended the cretaceous period has been a major priority in the scientific world, however, with enough modern day research, scientists have nailed the extinction of the Dinosaurs down to two major theories; the asteroid impact theory, and the volcanic eruption theory, both being extremely alike.