End Cretaceous Impact Hypothesis

8. The periods in which there were mass extinctions are Permian – volcanic eruptions which spewed lava and put CO2 into the air which warmed the climate an estimated 6 degrees Celsius. The resulting of oxygen deficiency. And Cretaceous – asteroid or comet

He narrowed his hunt down to a location in Denmark, where he had sent a colleague to perform an iridium analysis test at ("Asteroids and Dinosaurs: Unexpected Twists and an Unfinished Story," n.d.). When the results came back, Alvarez knew that whatever happened had not been a small-scale disaster. Once again, Alvarez was back to asking questions. What caused the increased iridium levels at the KT boundary? Except this time, he realized that his observations supported the ten year old hypothesis that had been proposed by paleontologist Dale Russell and physicist Wallace Tucker ("Asteroids and Dinosaurs: Unexpected Twists and an Unfinished Story," n.d.). They brought up the possibility of a supernova being the cause of dinosaur extinction. Supernovas are known to release high amounts of iridium, so such a hypothesis fit perfectly with Alvarez’s team’s discovery. However, the hope of having found a conclusion was short-lived. Luis Alvarez had mentioned that if said supernova had occurred that it would have released amounts of plutonium which would have been found alongside the iridium; no plutonium was found at either site. After more digging, the team came up with a new hypothesis ("Asteroids and Dinosaurs: Unexpected Twists and an Unfinished Story," n.d.). Perhaps an asteroid had struck Earth towards the end of the Cretaceous period, blowing enough dust into the atmosphere to

Dinosaurs ruled the earth for over 65 million years and thankfully for the human race, they became extinct. Ultimately, only a major catastrophe could completely wipe out an entire species, let alone an entity of dinosaurs and the debacle on the causes of dinosaur extinction have flooded the minds of paleontologists for centuries. Geologist and zoologist Stephen Jay Gould published “Sex, Drugs, Disasters, and the Extinction of Dinosaurs,” to compare scientific and speculative causes of dinosaur decimation. Personally, I found this passage very informational and enjoyed reading it. Gould provides three theories that capture the reader’s curiosity, allowing room for pondering in one’s mind.

The Cretaceous-Paleogene boundary that occurred around 65 million years ago marks one of the three largest mass extinctions in the past 500 million years. The hypotheses of Cretaceous-Tertiary boundary impact on Yucatán Peninsula, Mexico shows evidence in the Gulf of Mexico of turbidity currents, and giant waves occurring because of the impact. There is also other evidence that impact ejecta were distributed all over the world. The mineral that was ejected during this impact was iridium. Iridium is a mineral that is commonly used to indicate a rock layer from the K-T boundary. Iridium is only found naturally on extraterrestrial bodies. In addition to Iridium, shocked quartz is used to indicate the K-T boundary. Shocked quartz is unique and

The KT extinction asteroid impact, arguably the most recognizable asteroid impact ever known, also known as the “Chicxulub Asteroid Impact” from the name of the location the impact occurred.(Schulte et al., 2010) The event itself happened around 65.5 million years ago. It is widely accepted as the event that caused the mass extinction that marked the boundary

Large amounts of iridium – a chemical element that is not a part of the Earth’s crust composition – were originally found in rocks of Europe and United States, and have been found everywhere ever since. Iridium, common in meteorites, is a testable evidence of the disaster hypothesis. Gould continues that the Cretaceous debacle, which is one of five episodes of mass dying, occurred at the same time as the large comet might have smashed into the Earth. The author believes this is not merely a coincidence, rather, it is a proof of the cause-effect relationship. The demise of a wide range of habitats along with the extinction of dinosaurs gives an inestimable advantage to the disaster theory over other claims, the author adds. The comet struck the Earth, and habitats, from terrestrial to marine, died with geological suddenness. Finally, this hypothesis has had an impact on the study of an atomic war and its consequences. A nuclear war, Gould says, may cause a huge drop in temperatures and result in the extinction of humanity. Testable evidence, study, development, contribution – all this makes good science.

These techniques led to the discovery of the boundary between the two eras. A single thin layer of clay found within predominantly limestone rocks established this. By comparing the marine life found in, above, and below the clay, the marine life, like the dinosaurs, had been terribly affected by the extinction event. The percentage of life in the upper layers was dramatically lower than that in the lower. This was far more compelling than what was suggested by dinosaur’s fossils.

The Cretaceous-Tertiary extinction, also known as the K-T extinction, was a global extinction event that struck the Yucatan Peninsula at the end of the end of the Mesozoic Era, 65 million years ago. Walter Alvarez first discovered a meteorite big enough to be called a small asteroid that hit the Earth, creating the Chicxulub crater. Once the asteroid struck the North American continent, there were igneous rocks underneath the crater that contained high levels of a rare siderophile element, iridium. This catrostopic event had a massive effect on the environment, as several mammals, birds, and plants became extinct. It also caused an impact winter that made it impossible for plants and plankton to photosynthesis, as 75% of inland animals and 90% of marine species were affected. Not only did it cause an impact winter, but the asteroid also caused volcanic eruptions, climate change and sea level rise. Geologists have also found rich dinosaur, plant and marine fossils to illustrate the K-T extinction. This event not only caused species to become extinct, but it also had an adaptive radiation, as other species were able to diversify.

According to Gould essay, the theory of disasters is “a large comet or asteroid struck the Earth some 65 million years ago, lofting a cloud of dust into the sky and blocking sunlight, thereby suppressing photosynthesis and so drastically lowering world temperatures that dinosaurs and hosts of other creatures became extinct.’(50).The theory of disasters proves worthy of more research when compared to the theory of sex and drugs. This is because the disasters theory “generates tests, provides us with things to do, and expands outward” (55). Cowell’s hypothesis (the theory of sex) “has generated nothing for 35 years” because scientists can do nothing with it and the theory of drugs “will win a few press nots and fade into oblivion (54-55). Although talking about asteroids, dust and darkness is no more entertaining than talking about fried testicles or terminal trips “it’s the iridium – the source of testable evidence – that counts and forges the crucial distinction between speculation and science.”(55).The iridium bridges the gap between science and speculation because it is a source of testable evidence. The iridium is testable because geologist determined when high iridium first formed and related it to the comet that struck the Earth. Therefore, the theory of disaster is the most superior evidence for dinosaur extinction when compared to the method of sex and drugs due to its abundant

Over 98% of all organisms that have lived on Earth are now extinct. A mass extinction event occurs when a large number of species die out within a small time frame (relative to the age of Earth). Mass extinctions are intensively studied for both cause and effect, as there is usually room for debate regarding catalysts that precede the extinction and the massive influx of new biological species that follows. There have been five major mass extinctions, dubbed the “Big Five,” that have wiped out at least 50% of the species living at those times. The most well known mass extinction of the Big Five, with the decimation of every species of non-avian dinosaur, is the Cretaceous-Paleogene

“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…”

According to the research made by Alvarez (1980), it was due to an asteroid impact that single-handedly destroyed dinosaurs to extinction. Advocacy of this mechanism has been aided by the availability and tangibility of supporting evidence in the form of impact craters- the Chicxulub crater in the Yucatan Peninsula's date and timing of impact (dating produced an almost exact date of 65 million years ago), location, enormous size-170 km (Hildebrand et al.1991) and its high iridium content ( a metal not commonly found at the Earth's surface) make it seem that with a theoretical asteroid 10 km big caused the crater great damage at the end of the Cretaceous (Alvarez et al. 1980).

“Intrinsic gradualists” are scientists that believe that the cause of the Cretaceous-Tertiary extinction was mainly from Earth's natural process that gradually took place over several million years. The “Intrinsic gradualist” had two main hypotheses that are strongly supported till this day. The first hypothesis is volcanism. Studies have suggested that towards the end of the Cretaceous period, there was an increase in volcanic activity (Keller, 2014). This increase in volcanic activity could have blown enough ash and soot to block out sunlight, thus lowering the global climate. The magma arising from these volcanic eruptions are high in iridium, which are found throughout Earth in the Cretaceous-Tertiary stratigraphic boundary (Bajpai, 2000). Around this time of high volcanism, a mantle superplume deposited great amounts of basalt, which flooded into the Deccan Plateau, to form large lava beds, which are now called the Deccan Traps (Keller, 2014). The Deccan Traps cover about 200,000 miles, and at such large scale, these traps also dispersed tremendous amounts of dust and ash in the atmosphere (Keller, 2014). The second “intrinsic” hypothesis revolves around plate tectonics. During the Cretaceous-Tertiary time frame, the continental plates were drifting apart and experiencing large amounts of tectonic activity. As a result, large bodies of water, such as the Interior Seaway in North America, experienced regression (Nordt, 2003). This regression of the sea resulted in the increase in humidity, which was associated with the middle to high latitude cooling over several million years (Nordt, 2003). These “intrinsic” hypotheses support one another, because volcanism, in many cases, is a result of plate

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).

Rapid climate change also ends up on the suspect list of possible dinosaur extinction events. During the latter part of the Cretaceous Period continents broke up causing volcanoes to erupt and fill the sky with gas and ash resulting in a drastic climate change (“Dinosaurs Climate Change and Biodiversity”). The shifting of continents changed the Earth’s landscape, altering weather patterns and overall climate (“Dinosaur Extinction Theories”). Also, over a long period of time, climate gradually changed. Ocean habits changed, temperatures grew much more extreme causing scorching summers and frigid winters (Norell, Dingus, and Gaffney). Radical temperature changes like these led to a green-house effect, making life for the dinosaurs a lot