Liam Murphy - GEOL200 - Lab Assignment 07 [Marked]

4. Geoscientists think that the upper part of this valley was modified by a very large glacier early in the Pleistocene Ice Age, but that the lower part of the valley was primarily or exclusively cut by the Merced River. Of course, the water and sediment from every glacial episode in Yosemite Valley was carried away by the Merced River, so it had a significant amount of erosive power at those times. Examine your finished S profile E-E’. What part of the valley might you interpret as having been carved by the Merced River, and what part might have been modified by a glacier? That is below what elevation along profile E-E’ is the part of the valley that might have been cut only by the river? From elevation 4400 feet down appears to have a mare characteristic “V-Shape” valley that is seen with stream erosion valleys. From above elevation 4400 feet f‘e valley appears to have a shallower sloped valley which could indicate the modification via a glacier. Pa‘rt Two Complete activity 13.3 (Nisqually Glacier response to Climate Change): Answer questions A-D in the Laboratory Manual (pages 371-372). s A. Complete the following tasks to compile a data table showing the location of the end of the Nisqually Glacier relative to the Nisqually River Bridge at different times. 1. Measure the horizontal distance from the Nisqually River Bridge to each of the small yellow dots on Fig. 13.13 that show where the end (terminus) of Nisqually Glacier was in the past. Record your map measurements (in mm) on the data table in Fig. A13.3.1 fi\%flw See below. Use the bar scale on Fig. 13.14 and your knowledge of proportions to convert your map measurements (in mm) to distance measurements at full scale (in km). Record your calculated distances, rounded to the hundredth of a km, on the data table in Fig. A13.3.1 See below. B. Plot your data. 1. The vertical lines on the graph in Fig. A13.3.1 represent the years for which the data have compiled. The horizontal lines correspond to horizontal distances between the bridge and the glacier terminus in tenths of km. Carefully plot the data you have compiled on the graph as a set of points. See below. om Q‘QW : o i 2. Lightly draw a smooth pencil line through each of the data points in the correct sequence. See below. 3. Notice that the glacier terminus retreated up the valley at some times but advanced back down the valley at other times. Summarize these changes in a brief written description that includes the specific time intervals when the glacier retreated or advanced. 1963 — The river was recorded at 1.85km from the Nisqually River Bridge. 1966 — The river has retreated back up the valley by ~100m. Measuring 1.75km from the Nisqually River Bridge. S’ 1968 — The river has retreated a further ~30m up the valley. Now measuring 1.72km from the Nisqually River Bridge. Y 1971 'T The river has now advanced down the valley ~50m. Now measuring 1.77km from the Nisqually River ‘Bridge! ' - 1974- The river has advanced a further ~30m. Now measuring 1.80km from the Nisqually River Bridge. 1976 — The river has retreated up the valley by ~80m. Now measuring 1.72km from the Nisqually River Bridge. 1994 — The river has advanced ~210km. Now measuring 1.93km from the Nisqually River Bridge. A Liam Murphy WO\U\) = Unit 9: Glaciers and Glacation GEOL 200 Lab Assignment #7 Athabasca University Page 3 of 5 August 24t 2021