Banded Iron Formations and evolution of the atmosphere
The time between the formation of the earth and the beginning of the Cambrian(about 570mya) is a 4000 my long period known as the Precambrian, this includes approximately 90% of geological time of which we know very little about as pre-Cambrian rocks are poorly exposed, many have been eroded or metamorphosed and fossils are seldom found.
The Precambrian has been divided into 3 Eons: 1.Hadean (4600-3800 mya of which there is no rock record) 2.Archean 3800-2500 mya) 3.Proterozoic 2500-570 mya.
The present atmosphere is greatly depleted in Ne, Xe and Kr which are inert gases that should be preserved in the atmosphere. This suggests that the earth’s initial atmosphere was lost early on either by boiling away during the magma ocean event or by being carried away by intense solar wind in the early solar system. At the end of the Hadean the present atmosphere and hydrosphere began to develop from volcanic emissions. It was during the proterozoic that a critical change occurred in the atmosphere, when it changed from a trace oxygen content of the Archean atmosphere to above 15% oxygen by 1800 mya.
It is widely believed that this change was brought about by the emergence of cyanobacteria which had adapted to create energy from the sun by photosynthesis(probably due to a shortage of raw materials for energy), as a result they had began to poison the earlier anaerobic bacteria or archea with their waste product; oxygen.
This essay will focus on the evolution of the atmosphere and its relation to the banded iron formations of the late Precambrian.
Banded Iron Formations
Cloud (1968) calls Banded Iron Formations, rhythmically banded chemical sediments of large, open water bodies that take different aspects but most characteristically consists of alternating layers of iron- rich and iron-poor silica. It is present in some of the oldest volcanic sequences (greenstone belts ca 2800 mya) and is a common sediment type formed until approximately 1800 mya. Although some younger formations with similar structure can be found there is great distinctions between them and the BIF’s of the Precambrian.
The BIF’s can occur in sequences which range from 15 ferric iron.
Some people believe the iron to be of volcanic origin, weathered and transported into the oceans or e...
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...oss a threshold from one steady state to another.
Conclusion
The complexities and conflicting arguments involved in relation to the evolution of the atmosphere and its links to banded iron formation are hard to over emphasise. It is a topic which still has a long way to go and one which may never be conclusively understood due to the lack of evidence from the Precambrian rocks (or lack of rock record altogether).
However the general consensus seems to be that for a period of over a 1000 my until 1800 mya, conditions where favourable for chemical deposition of iron, there was distinct changes occurring in the atmosphere with rapid increase in free O2 coupled with a fundamental change in the evolution of early life from anaerobic bacteria to aerobic cyanobacteria.
The origin sequence and connection of these events are the issues that are currently in debate. Most are in agreement that they are all linked and that O2 levels are a key factor in the formation of banded iron formation, the problems arise when trying to distinguish when and how O2 began to be produced, the question arises, which came first the oxygen producing bacteria or the oxygen causing life sensitive to it to adapt?
...under H₂O-undersaturated conditions, water was structurally bound up to the greenschist facies and then at the start of anatexis the excess water maximized the amount of H₂O-undersaturated melt generated. Furthermore the dissolution of accessory minerals can provide melts with structural components which in turn give clues about melting history and melting conditions, even during rapid melting. The analysis and mass balance of trace elements found in the glasses and residual phases and melt extraction data, together provided evidence that significant amounts of LILE were retained in residual feldspars and biotite crystals up to a high degree of partial melting of the crustal protolith. This is interpreted as meaning that higher temperatures of partial melting are needed to more efficiently differentiate the crust in these mostly incompatible trace elements.
years ” (Quimby 2), since this epoch involved the fundamental evolution of mankind to the present. It is important to
The conflict approach is one that puts an emphasis on inequality and competition between social groups that leads to problems. Throughout the course of the Poor Kids documentary the conflict approach can be implemented to help explain why childhood poverty is caused. Conflict theorist can point to Brittany’s family as an example of how competition between social classes can cause poverty. Brittany’s father was working for a company that decided to scale down in order to better sustain itself during tough economic times. As a result, Brittany’s father lost his job with the company since he did not hold a high position within the company. Brittany’s family when her father had his job was not considered a high class family as far as income and luxury goes. The video did not specifically state what class family they were, but it can be inferred that they were probably a low middle class or low class family. So, because her father was not holding a high position and was not considered of high social importance, he was let go as if he was almost expendable. If he was of high social class and held a higher or more important position within the company than he probably would not have been let go. This refers back to competition between social classes (Turner). The old cliché, the rich get richer and the poor get poorer can be thought relevant in this situation. Also, the conflict approach can be applied to the part of the video in which Brittany’s dad was unsuccessful in finding a job. Her dad went online and submitted an array of applications to a multitude of different companies in hopes to get hired. Unfortunately, he didn’t hear anything back from any of the companies and was not offered a job. His lack of success in finding a job can be explained in various ways. The conflict approach would point to his social status as a key reason in why he was unsuccessful. It can said that because Brittany’s father was not of a high social class or group he wasn’t given as
The Cambrian explosion refers to the speedy diversification of new forms of animals arising within the fossil record in the span of about 20 million years. This may not seem to be the shortest time frame, but in an evolutionary sense it was lightning fast. Some of the early fossils are unusually intact and very well preserved. Two of the more famous locations of Cambrian fossil discoveries are the Burgess Shale discovered by Charles Walcott on August 30, 1909 in Canada and the Maotianshan Shales in Chengijang, china.
The Carboniferous Period was a time period in the Geological Time Scale that came after the Devonian Period and ended at the beginning of the Permian Period. It lasted from 359 to 298 million years ago. The Carboniferous got its name from the large amount of coal deposits that were found during this time scale. In North America, the period is often separated into two, the Mississippian and the Pennsylvanian.
Buddhism descend from ancient India, the creator is Sakyamuni. Historically, the Buddhism is established around the 700 Before Christ era. Sakyamuni gives speeches to the local people. Gradually, Buddhism is spread to all around the world. As author illustrates in his writings," The history of Buddhism spans almost 2,500 years from its origin in India wi...
In today’s world, there are various religions that are worshipped by millions of devout followers every year. Of these religions, two of these include Buddhism and Christianity, which have dated back for thousands of years. According to. Experiencing the World 's Religions and The World’s Wisdom: Sacred Texts of the World’s Religions, both Buddhism and Christianity originated through a single enlightened leader and were known as each religion’s teachers: Buddha and Jesus Christ. Both of these prophets became what shaped their respective religions and had a large influence on being bringers of hope to the world and proclaiming peace among the nations.
Rooted in thousands years of tradition, rituals and practices Islam and Buddhism are at the forefront of the major World Religions. Their influences on culture, politics and society have reached far and wide; from quaint villages in the Middle East to roaring metropolitan areas of China and Japan. Islam is born out of the teachings of the prophet Muhammad, while Buddhism focuses on the teachings of Siddhartha Gautama. Although many people claim to know these two religions, the reality is that many continue to not realize the great differences between them. While both religions seem very similar in nature, their main differences come from their sacred texts and ritual practices.
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.
Although we can see that the two beliefs of Christianity and Pure Land Buddhism have similar beliefs, we also can see that they do differ in some major areas. I think that it is obvious to see that the Nestorians who brought Christianity to China and Japan had an influence on the Buddhist people during the sixth and seventh century. The religions have their major differences but we can see that throughout the scriptures that the main Idea of unseen faith is the central idea to the religion. Some may say that they are two very different religions but I would differ saying they have very much in common.
The beginnings of modern processing of iron can be traced back to central Europe in the mid-14th century BC. Pure iron has limited use in today’s world. Commercial iron always contains small amounts of carbon and other impurities that change its physical properties, which are much improved by the further addition of carbon and other alloying elements. This helps to prevent oxidation, also known as rust.
There are several theories about how the Cambrian Explosion started. There were major changes in marine environments and chemistry from the late Precambrian into the Cambrian, and these also may have impacted the rise of mineralized skeletons among previously soft-bodied organisms. One theory as to what happened is that oxygen in the atmosphere, with the contribution of photosy...
Many parents believe that uniforms will only stifle the students creativity. They will not be allowed to freely express themselves with the colors that they wear as well as the clothing itself. If a child is feeling particularly happy that day, he or she may want to wear their favorite outfit to express themselves and the way that they feel. If all students wear uniforms, the entire school will all look exactly the same, which takes away all creativity and suppresses individuality.
...deposition and blanket of sediment kept the organisms compressed with little exposure to oxygen for decay. If life was predominately terrestrial during the Cambrian, the organisms predictably would have been left untouched after death long enough to decay, preventing the fine preservation of many soft-bodied organisms. Fortunately enough, it was marine life that dominated the Cambrian (Scott, et al., 2000).
...ent-teacher relationship. Less distractions and a more respectful school setting for children would certainly help them concentrate on their studies more effectively. Also, with blurred socioeconomic lines, children would not have to worry about being bullied because they wear the same couple of shirts every day, as that is all that they own, or the wrong brand of jeans. All children being dressed the same would lend itself to a sense of camaraderie instead of competing to see who is dressed the best. A reduction in bullying and violence, less peer pressure, lower costs to parents, increased academic scores, and a sense of belonging are all reasons that I am certainly in favor of the implementation of school uniforms in our public school system. With so many positives, maybe the real question should be why don’t more public schools have school uniform policies?