Last Deglaciation

Last Deglaciation







Last Deglaciation


The study of historical events is necessary in the understanding of the present environmental conditions and the anticipation of possible changes of the environment in the future. This however, requires careful analysis of scientific evidence, which is used in the reconstruction of past events and more specifically prevailing climatic conditions. Scientific evidence refers to evidence that is generally used in the support or in the disagreement of scientific theories and hypothesis. Coral reefs and pollen grains are used in the support of various theories pertaining to the existence and impacts of the last deglaciation.

Coral Reefs

Explain how the scientific evidence is used to reconstruct conditions of the Last Deglaciation

Coral reefs are one of the scientific evidences used in the reconstruction of conditions prevailing during particular times in history. The underlying idea is based on the ability of corals to build their hard skeletons using a mineral called calcium carbonate. This mineral is mainly found and extracted from seawater. The compound making up the calcium carbonate contains a sizable amount of oxygen, isotopes of oxygen and trace metals. These are later used in the reconstruction of the temperature of the water during the formation of the corals together with the composition of the atmosphere. The indirect temperature recordings can then be used to reconstruct the prevailing climatic conditions during the time the coral was in existence.

Scientific research employs the knowledge on coral reefs to identify the prevailing conditions during the last deglaciation.

Examine whether or not scientific studies actually support the scientific evidence

A careful examination of scientific and peer-reviewed journals indicate that the scientific evidence is indeed supported as a reliable source. Fossil coral reefs are a reliable source in the accurate reconstruction of past conditions (Roberts, 1998). These conditions include seal level variations, prevailing climatic conditions and changes and environmental perturbations. The study of coral reefs provides some of the most reliable and precise information pertaining to changes in the sea level. The main supporting evidence towards this claim is that the coral reefs are known to exist within very strict ecological requirements (Allan and D’Arrigo, 1999). When these conditions are slightly changed, then the coral reefs die.

Studies indicate the coral reefs live in regions where the water is well supplied with oxygen; the water also needs to be clear and not below fifty meters of the sea column (Bretz, 1923). Coral reefs also require average temperatures ranging from eighteen to thirty-five degrees centigrade with a very narrow salinity range of between thirty-five to thirty-six per ml for existence. Any variations from the above conditions will lead to a change in the coral reef development and composition (Westbroek, 1991). This enables the coral reefs to give accurate information regarding the sea level, temperature changes, salinity and oxygen concentrations at different periods in history. Intelligent analysis of this information enables one to have an accurate reconstruction of past climatic changes and the environment. Study also indicates that the information derived from the study of coral reefs rhymes with information gathered from other techniques in the verification of datasets (Lee, 2010).

Discuss problems/difficulties/potential pitfalls in using this type of evidence for the reconstruction of paleoclimates

Despite the advancements in the use of coral reefs in the reconstruction of paleoclimates however, several issues still plague this piece of scientific evidence. The first issue is that of replication. Research indicates the presence of several published and unpublished instances on the existence of isotopic and elemental time series. This is done using corals hailing from the same colony or adjacent heads. Analysis indicates that most exhibit similar results. For there to be accurate findings, there needs to be correlation of similar results. When there are disagreements in the results, then the findings become ambiguous. Acceptable findings are thereby only deduced in instances where there are multiple records indicating similarity in the findings. Only such researches should be used in the reconstruction of climatic history. Currently, there has not been such a deduction in instances where the corals date back to more than a hundred years. Thus, there brings about the need for multiple coring and subsequent analysis for the development of accurate period analysis based on cross dating.

Another underlying issue is the species issue. There lacks in depth research on the utility of many coral reefs. Current trends in historical research delve on the over reliance of just a few species of coral for deductions pertaining to the development of climatic records. There are instances where different taxa yield results that are similar to one another. There are other instances where some species have failed to yield results or reproduced even when they are reared in adjacent colonies to others. In other instances, certain species have required very specific sampling procedures for there to be accurate results. Under general circumstances, only one particular species of coral known as the Porites species, which are mainly used in studies in the Indian and pacific oceans have yielded reproducible results. This raises the need for more research and thus a better understanding of the processes that are involved in the development of the different coral species. This could end up being the answer to having specific sampling procedures for the species that fail to yield similar results (Smith, 2002).


Explain how the scientific evidence is used to reconstruct conditions of the Last Deglaciation

Pollen is used as scientific evidence in the reconstruction of past conditions. This is done in the realm of Palynology. This is the analysis of fossil pollen and is used to investigate changes in climate and the environment in the past. Each particular species of plants is known to develop unique pollens with distinct sizes and shapes. The scientist who studied the last deglaciation used these shapes to identify the particular plants from which the pollen grains had been produced. This was made possible by the fact that pollen grains take a lot of time to rot. The well-preserved pollen grains were recovered in the sediment layers of blanket peat around the scrubland and in Missoula, Montana. Careful analysis of the pollen enabled the scientists to deduce the type of plants growing at the time the sediment was deposited. This later led to the reconstruction of the prevailing climatic conditions at the time based on the type of plants found on the layers. In the formation of the scrubland, it was found that the pollens belong to plants that share the similar climatic and environmental factors. This helped to inference that the occurrence did not take along period of time but a relatively short one (Santos, Romani, and Jalut, 2000).

Examine whether or not scientific studies actually support the scientific evidence

Analysis of peer reviewed journals and scientific articles reveal the fact that pollen analysis is widely accepted as a reliable scientific evidence for the support of scientific hypothesis and theories. The fact that pollen grains are resistant to decay enable scientists to study pollen grains shed many years in history (Cronin, 1999). Another aspect of pollen is that are they easily dispersed and are produced by plants in very large numbers. This aspect makes it possible for them to settle and accumulate on undisturbed surfaces such as lake sediments and peat bogs. The presence of minimal oxygen concentrations in peat bogs and lake sediments further decreases their rates of decay. Scientific research indicates that the sediments accumulate over time and thereby forming several distinct layers (Lamb, 1982). This creates a vertical profile of the distinct history of the different vegetation present in the area during different time zones.

Research indicates the presence of pollen grains dating back to four hundred million years in history. Pollen grains do not share genetic structure as they come in different and distinct shapes and sizes. Scientists examine the shape structure and texture to identify the particular specie of plants from which the pollen grains were produced. This information is also used in deducing when the pollen was produced. There is also the aspect of adaptation of plants to certain environments that assists in reconstruction of climates. This adaptation to particular climatic conditions makes it impossible for these plants to thrive after changes in the environment. This also results in the appearance of new species of plants that are better suited to the prevailing climatic conditions. Scientists use the changes in plant species and the pollen deposited to deduce changes in the climate (Herlihy, 1980).

Discuss problems/difficulties/potential pitfalls in using this type of evidence for the reconstruction of paleoclimates

The use of pollen analysis to deduce climate patterns in history is however plagued by several potential pitfalls. There lie some inaccuracies in using the sediment for the deduction of paleoclimates. One particular one is the possibility of deducting that the presence of an abundance of pollen deposited in a particular field to mean that the parent plant to the pollen was abundant in the area during the deposition. This is an inaccurate deduction as different plant species produce pollen in different amounts (Pardee, 1910).



In conclusion, we find that coral reefs and pollen grains have been adequately analyzed to justify the last Deglaciation and configure the prevailing climatic conditions during that particular time in history. Coral reefs exist under only specific conditions. The study of the fossil fuels is used in the reconstruction of the temperature of the water during the formation of the corals together with the composition of the atmosphere (Allison, 1933). On the other hand, pollen grains are also used in the determination of the prevailing climatic conditions during the deglaciation period.



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Allan, R., and D’Arrigo, R. (1999). Persistent ENSO sequences: how unusual was the 1990-1995 El Nino? Oxford: Blackwell.

Bretz, J. (1923). The Channeled Scabland of the Columbia Plateau. Journal of Geology, 31, 617–649.

Cronin, T. M. (1999). Principles of Paleoclimatology: Perspectives in Paleobiology and Earth History. New York: Columbia University Press.

Herlihy, D. (1980). Climate and Documentary Sources: A Comment. The Journal of Interdisciplinary History, 10 (4), 713-718.

Lamb, H. H. (1982). How can we reconstruct the past record of climate? Climate History and the Modern World. London: Methuen.

Lee, C. (2010). Reconstructing the climate of medieval Europe. New York: Columbia University Press.

Pardee, J. T. (1910). The glacial Lake Missoula. Journal of Geology, 18, 376-396.

Roberts, N. (1998). “Reconstructing Holocene Environments”, in: The Holocene: An Environmental History. Oxford: Blackwell.

Santos, L., Vidal, J. R. and Jalut, G. (2000). History of vegetation during the Holocene in the Courel and Queixa Sierras, Galicia, northwest Iberian Peninsula. Journal of Quaternary Science, 15, 621-632.

Smith, I. R. (2002). Diatom-based Holocene paleoenvironmental records from continental sites on northeastern Ellesmere Island, high Arctic, Canada. Journal of Paleolimnology, 27, 9-28.

Westbroek, P. (1991). Life as a Geological Force: Dynamics of the Earth. New York, NY: Norton.





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