Glacial periods “Nebraskan, Kansan, Illinoian, and Wisconsin
Glacial Periods “Nebraskan, Kansan, Illinoian, and Wisconsin.”
The Glacial period represents a geological age that was having the long-term drop in the temperature of the earth’s surface and the atmosphere; the reduction in the temperature of the earth surface and its atmosphere resulted in the expansion of the ice sheets in the continents, polar and in the alpine. These periods had too many cold climates, and it was called glaciations, which means the presence of too much ice sheets within the northern and the southern hemispheres.
Most likely some countries are still experiencing the ice age period since there is the existence of Greenland and the Antarctic ice sheets as expressed Leeman (860). In the last few million years, the ice age has been used to refer to the extensive cold periods that the people in North American and the Eurasian continents experience. Due to this, the most recent ice age experienced in the last 20000 years ago.
A glacier is a big body of ice that is in motion, and it is formed on land. Glaciers do transport materials as they move while carving and sculpting the earth during its movement. As they move, the lower layers of the ice melt and materials are deposited, this is called till Cooper, William S., and Richard Foster (470). As a glacier retreats all the materials in the glacier are deposited and placed in a new location far from where it came. Glaciers are the cause for interesting landforms and geology such as there being gold in Ohio.
There were four periods of glaciations that transpired during the last ice age that is called the Pleistocene Epoch. The Nebraskan glacial stage is the oldest, and it was followed by the Kansan. These two stages are also known as the Pre-Illinoian era. Preceding the Nebraskan and the Kansan eras was the Illinoian, which arose around 300,000 years ago. The most recent glacial period to occur in North America was the Wisconsin as Leeman (860) explained. This glacial advance covered much North America and extended down to the Ohio River. In this article, I am going to discuss the periods of glaciations starting from the oldest glacial period to the most recent glacial period. The glacial periods include; Nebraskan, Kansan, Illinoian, and Wisconsin.
Nebraskan Glacial Period
It is the major division of the Pleistocene period and deposits in the north of America. It occurred in the period between 2.6 million to 11700 years ago. It is the oldest glacial stage in the glaciations in the north of America. It was named Nebraskan due to deposits of the glaciers in the state of Nebraska. But then the glaciers representation in that state are not well developed. The Nebraskan is not known throughout the American but then its position as one of the first four glaciations periods in the Midwestern states is well known, and much are still there to be done to describe its position more accurately. The deposits of the Nebraskan are well developed in the Nebraska, Missouri, Kansas and Iowa. Outside these states, the deposits that can be considered as being Nebraska are not valid, and the Nebraskan deposits must be rich in clays.
Kansan glacier represented a stage and the part of the early theoretical climatic and chronological structure that poised the four glacial and the interglacial stages. Kansan glaciations were adopted by the early geomorphologists and the quaternary geologists to help them subdivide the glacial and nonglacial deposits that were experienced in the north-central United States.
Kansan glacier developed in the period between 1894 and 1909; it was based on a model that assumed that Pleistocene deposits had only two glacial tills and only one volcanic ash that could be easily established in Nebraska and Kansas. For instance, The Kansan till, that describes the Kansan stage that had the two of the upper glacial tills, and the Nebraska stage represented the lower two glacial tills. The two tills were separated by a single paleosol that grew in the Nebraskan and the integral deposits as explained by Leeman (860).
Research results show that many paleosols separated the Nebraskan and Kansan tills, and they existed. Some other glacial tills studies in Kansans explained that at different points, the same glacial till could be called Kansas or Nebraskan. The paleosol was also found to be covered with small glacial till that were the same as those of Nebraskan. This led to the till being considered to be Nebraskan till. Due to such the basic assumptions that the Yarmouthian had the interglacial while Kansas was having glacial and Aftonian having interglacial as Nebraskan having glacial came out to be lacking scientific facts. It then forced the nomenclature to be abandoned by the quaternary geologists in the North of America. And thus they merged into the pre-Illinoian stage.
The Illinoian Stage
This stage represents the period of geological between 191000- 130000 years ago. It was during this Pleistocene period when the sediments containing Illinoian freezing lobe got deposited. It is also the period when the glacial tills and the outwash that contains the bulk of Glasford formation came together to form the Illinoian Glacial Lobe. It was established in Illinois and consisted of three till groups that were the same as Glasford Formation. The pre-Illinoian tills were overlaid i.e. the banner formation were overlaid to effect the development of Paleosol. Due to this exposure, the Illinoian Glasford formation led to the development of interglacial Sangamon soil. The Illinoian stage can further be subdivided into Liman sub stage, Monica substage and the Jubilee sub stage.
The Illinois stage has two glaciations e.g. the early Illinoian stage that consists of the marine isotope and the late Illinoian glaciations stage that constitutes the marine isotope as explained HALLBERG (14). This interpretation also explains that Illinoian glaciations stage must have started some 300000 years ago and might have ended about 130000 years ago. The Illinoian glaciations stage is temporarily the same as the middle and the late Wolstonian Stage in the British Isles. During the stage of Illinoian, the Laurentide iceberg managed to cover about 85% of the land of Illinois. At the maximum of this stage, the ice reached even the southernmost part of North America. At times, the ice sheets could lay mostly to the south as pointed out by Richmond, and David (190).
It represents the most recent glaciations witnessed in the north of America ice sheet complex. It contained various ice sheets like the Cordilleran ice sheet that originated from the northern part of North America Cordillera. It had the initial ice sheet that covered most of the Canadian Arctic Archipelago; Greenland ice sheet and also the Laurentide ice sheet that managed to cover high latitudes of the central and North Eastern part of North America. It extended its occurrence from the beginning of 85000 to 11000 years ago. Such was witnessed between the Emian stage and the Holocene that is the current interglacial. The Wisconsin glaciations managed to alter the geography of North America especially at the north of Ohio River. It also covered most parts of Canada, Washington, Idaho, and Montana. Some of the grooves courtesy of the glaciers are still evident on the Kelleys Island and in the New York central park.
Davis and Motut express concern that there exist two movements of the Wisconsin i.e. the early Wisconsin and the late Wisconsin. The early Wisconsin marked the biggest and its effects extended to both the west and the south. It had recoiled a bigger distance before it arrested. It did away with the Illinoian topography and extended over to other places. On the other hand, the late Wisconsin ice sheets moved towards the west. It could be due to the alterations in the accumulation center that the ice sheet displayed the changes in the topography especially in the early stages and the changes in the mass of the ice in the North may have fuelled its encroachment to the west.
Conclusions Glaciers present themselves in different sizes and shapes. The same ice sheet can have a varying hydrological, thermal and dynamic characteristic. Glaciations can be witnessed in any part of the world ranging from the poles to the equator; most parts of the world have experienced the effects of glaciations at some point as pointed pout by Leeman (860). Currently, glaciers are tending to occupy less part of the planet as compared to how it did in the past. All in all, it affects the environment negatively across the globe. Our consistent understanding of the glaciers and its effects help us have the good understanding of the world environmental pattern.
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Richmond, Gerald M., and David S. Fullerton. ‘Summation Of Quaternary Glaciations In The United States Of America’. Quaternary Science Reviews 5 (1986): 183-196. Web.
Leeman, William P. ‘The Isotopic Composition Of Strontium In Late-Cenozoic Basalts From The Basin-Range Province, Western United States’. Geochimica et Cosmochimica Acta 34.8 (1970): 857-872. Web.
‘Quaternary Glaciations: Extent And Chronology: Part 1: Europe’. Choice Reviews Online 42.07 (2005): 42-4043-42-4043. Web.
HALLBERG, G. ‘Pre-Wisconsin Glacial Stratigraphy Of The Central Plains Region In Iowa, Nebraska, Kansas, And Missouri’. Quaternary Science Reviews 5 (1986): 11-15. Web.
Davis, John, and Bernard Motut. Glaciers And Glaciation. Coquitlam, B.C.: Classroom Video, 2001. Print.