September 27, 2002
NSI, Section G
What are we standing on?: The Glacial Explanation.
We will collect samples from the bluff in Pfeffer Park, Four Mile Creek, and from Columbus. The purpose of this lab is to measure the percentage of grain size populations, the porosity of sediment, and to analyze the types of glacial sediment found in our samples. Our hypothesis is that we will find end moraine, end moraine is sediment dropped by retreating glaciers, around the bluff and glacial sediments in Columbus. We also believe that most of the sediment we find will be igneous rock from central Canada; we will do this by comparing the rocks we find to the bedrock of Canada (http://sts.gsc.nrcan.gc.ca/urban/bed_regional.asp). Originally we did not plan of doing this project; we were planning on doing a heat energy study on Peabody Hall. But the recent change in temperature changed our minds and altered our course of action. Our team member Jason, who has an interest in geology, came up with our current lab. Jason noticed the varied topography of this region and wandered if it was the result of glacial deposits and that is how the idea for our lab originated. We decided to study the specific questions above because they seemed interesting.
We plan to accomplish a classification of the types of sediment in our study region and determine where these sediments came from. This lab is relevant to us because we live in an area with glacial deposits. This research is interesting because it is fascinating to know what you stand on and what is underneath you and to learn about a part of Earth’s history.
Relevance of your Research Question
This topic relates to the regional environmental concerns of the area. By knowing what kinds of glacial deposits are in a specific area one can prevent such major issues as groundwater contamination and mass wasting. If the area in which one lives is mainly glacial sediments, knowing what types of sediments are deposited can help you chose city water over well water, or know to watch for soil creep, which is the movement of clay-based soil down a slope, around your home. By figuring out what types of deposited sediments are in a given area, one can also infer the glacial environment of the past. This helps further our knowledge of history and what may happen in the futur. Relating these findings to fossil remains and archeological sites around the area might also help understand the biology, ecology, and culture (if any) of the area.
Thousands of years ago the last glacial advance retreated from the edges of Ohio, but not without leaving us reminders of its presence as well as of its previous travels. Before that time, not long ago in the span of earth history, these monolithic structures of ice dominated the high-latitude areas of the world (Bennett and Glasser 7 1996, Menzies 17 2002). Inching their way across the land, these formations covered areas for miles around with ice. The oldest substantiated evidence of this widespread glaciation can be found in rocks dating back to the Paleoprotozoic era in the areas of North America, Finland, South Africa, Australia and India (Bennett and Glasser 18). Glaciers retreated with climate changes and also created mass flows of water that affected the landscape as well, creating U-shaped river valleys as well as depositing the various sediments that were integrated slowly into its mass over the course of its travels. This process of glaciers depositing their various sediments is called glacial deposition, and is something that the Ohio region is very rich in.
”The fundamental characteristic of a glacier is that it is capable of moving on its own. A glacier flows to reach and maintain a gravitational equilibrium form, as material is moved from the accumulation zone to the ablation zone” (Martini, Brookfield and Sadure 49). As a glacier moves along, its great mass is able to scrape sediments from the ground and absorb them into itself. Sediments may also fall from sidewalls of valleys, or even be carried on the wind to land on the glacier (Martini, Brookfield and Sadure 97). Large glaciers are know to carry more sediments than small glaciers, due to their sheer mass allowing them to dislodge rocks beneath them as well as carve away landscapes and cause more rock to fall onto them. Eventually the climate changes caused the glaciers to retreat. This process caused the glaciers to deposit all of these collected sediments in various areas based on the stage of its retreat as well as how close specific sediments were to the surface of the glacier. This sediment is deposited through meltwater, the type of which is determined primarily by the distance from the ice margin, or till, which is deposited by the glacier directly (Bennett and Glasser 210). Sediments deposited by meltwater tend to become finer as they are further away from the glacier, because the larger materials settle out and move slower than the finer materials, while till comes in a variety of forms, like deformation till or ablation till (Martini, Brookfield and Sadure 101-104). These many different deposits come in many types, such as freefall deposits, talus deposits, or subglacial sheet flow deposits (Ashley, Shaw and Smith). Under normal conditions sediments are distributed unevenly with increasing sediment concentration settling more toward the bottom, with thick light layers and thin dark layers in succession, suggesting that the lighter deposits are made during the summer while the darker ones are deposited during the winter. These deposits are made into many different formations, depending on their shape and size. Many different types exist, but the most common are known as Moraines, which form both under actively moving glaciers as well as stagnant ice, and are the most common formations in the Ohio region.
Materials and Methods
We plan to study the glacial sediments deposited in the area by the Wisconsin glacial advance. We will take several samples of the glacial deposits and study the sediments in many ways. We will study the grain sizes of the samples, the porosity of the sediment, and the rock types of the sediment. We will put this information in a data sheet and compare the separate samples with each other. We will also infer on the location of the glacial erratics we find by looking at the bedrock of areas to the north of the depositional area. This information is statistically sound because we are coming up with quantitative numbers for the samples of glacial sediment. The reason we are doing the many types of samples, both quantitative and qualitative, is to more readily compare the different samples we get. We don’t plan to date the samples of when they were they deposited because we would not be able to do that with our recourses, and dating deposited samples can get tricky. We do plan to study the porosity of the sediments because ground water routinely flows through the area and it is import to study how much of that happens. Our data will be unbiased because we have nothing to prove from this, or gain from this study. The data that is collected by the class will be very trustworthy because we will use a sediment/rock identification sheet and easy instructions on how to collect the data accurately. We plan to take several samplings so as to squelch any inconsistencies.
The materials that we use such as a rock/mineral identification book, graduated cylinder, ruler, shovel, and soil identification book will be instrumental to our study. The rock/mineral ID book will help us identify the glacial erratic we find, the graduated cylinder will help us find the porosity of the sediments, a ruler to measure the grain size of rocks, a shovel to dig out the samples, a sediment sifter to find the percent of grains sizes in the sample, and a soil ID book to analyze the soil for ground water intrusions. The class will be helping us take samples and analyzing samples in the field at the Pfeffer Park ‘cliff’ region. The class will be asked, given different types of glacial sediments, what kind of glacial sedimentation exists.
Here is a sample of our data sheet:
Sediment sample area Avg. 'pebble' size Porosity %
Sediment sample area Rock type Number of rocks
Sediment sample area Grain size grain size amount
Week 6 ‹ rough draft of proposal done
Week 7- gather materials and make lab papers for class + research
Week 8 ‹ work on lab packet/take samples
Week 9 ‹ Finish lab packet / take samples
Week 10 ‹ Take samples
Week 11 - Analyze samples
Week 12 ‹ Analyze samples
Week 13-15 ‹ Work on finishing up the report
The type of statistical data we used for this project may be greatly different than other groups because we used equations that generally only work for grain size analysis. Our data is almost entirely in the φ (psi) numbers which is just -log2 times the diameter of the grain. Later figures show how this data set’s φ numbers were determined.
In our initial observations we see that the sediment collected from Four Mile Creek is different from the two other sediments collected. This statement is based on several different levels of observation that will be shown here. Firstly, in the porosity of the sediments, seen in figure 1, varies greatly only between Four Mile Creek, which is at 36% and above the standard deviation unit of the total averages. The equation we used for this is just V(Amount of water need to saturate sample) / V(amount of sample). In figure 2 one can see the differences between Four Mile Creek and the other sediments on the averages grain size, Four Mile Creek’s is much larger than the other two and once again above the standard deviation unit. In the standard deviation graph, figure 3, one can see that Four Mile Creek also shows a marked difference in data and again, is outside the deviation of the total samples. The equations need to get Figure 2 and 3 are a bit different, they were:
(φ84 - φ16)/4 + (φ95 – φ5) / 6.6 = Standard Deviation
(φ84 + φ50 + φ16) / 3 = Graphic Mean
Our data also includes a figure of porosity plotted against grain size, which shows a general trend of larger grain size population equaling greater porosity, Figure 4. Qualitatively we did not find a whole lot of non-native rock species in our samples, we found a greater amount of native rock species.
Our results do not conclusively prove out hypothesis. Four Mile creek is not within the range of our other samples and in fact fall outside the range of glacial sediment on the standard deviation calculation. Glacial sediments are poorly sorted, so the Std. Dev. sample should be above 2, but it falls below 2 at 1.73. This suggests that Four Mile Creek sediment is not glacial sediment. On the other hand, qualitatively we take rock samples and find non native rock types in the sediment such as large pebbles of granite. This sediment had to have been transported there some how. Its possible that it was carried down stream during a flood event and deposited there or that the sediment has interacted with the water table to the point where the smaller grains of sediment were carried away. Our data seems to support this. It is possible that this interaction happens a lot in many other areas and it is a further area of study that would be interesting. The porosity and grain size graph that we got is also something else that could be further studied. The graph is almost a straight line and it would be interesting to see if that continues above and below our scale. Our qualitative study also would be something to expand on, to study the mechanism in which greater amounts of native rock is deposited in an area by glaciers.
Overall the study that we have done as helped us discern what we are standing on, (Will not put a corny foundation of our learning sentence here), and what we aren’t… like a whole lot of igneous rock.
1.)Ashley, Gail M., John Shaw, and Norman D. Smith, eds. Glacial Sedimentary
Environments: Sept Short Course No. 16. Tulsa: Society of Paleontologists and Mineralogists, 1985.
2.)Bennett, Matthew R., and Neil F. Glasser. Glacial Geology: Ice Sheets and Landforms.
West Sussex: John Wiley & Sons, 1996.
3.)Jopling, Alan V., and Barrie C. McDonald, eds. Glaciofluvial and Glaciolacustrine
Sedimentation. Tulsa: Society of Economic Paleontologists and Mineralogists, 1975.
4.)Martini, I. Peter, Michael E. Brookfield, and Steven Sadura. Principles of Glacial
Geomorphology and Geology. Upper Saddle River: Prentice Hall, 2001.
5.)Menzies, John, ed. Modern & Past Glacial Environments. Oxford: Butterworth
6.)Mickelson, David M., and John W. Attig. Glacial Processes Past and Present. Boulder:
The Geological Society of America, 1999.
7.)Dr. M. H. Hills at Jacksonville State University. 25 May 2001. Glacial Deposition. 26
Sept. 2002 www.jsu.edu/depart/geography/mhill/phylabtwo/lab11/depositsf.html.
Terrain Sciences Division. 29 July 2002. Geological Survey of Canada. 26 Sept. 2002
8.)The Geography Exchange. 29 Jan. 2000. Moraine. 26 Sept. 2002
9.)The Geography Exchange. 23 Jan, 2000. Erratic. 26 Sept. 2002
10.)Natural Resources Canada. 26 July, 2001. “Bedrock Geology”. http://sts.gsc.nrcan.gc.ca/urban/bed_regional.asp.
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