LAB K

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School

University of Colorado, Boulder *

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1030

Subject

Geography

Date

Apr 3, 2024

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pdf

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Uploaded by MajorSkunk3919

PRI N S VI VT R VET| L 53% @ ) Q [€7Ye] [oTe\ VAU (OO N IE:T o o] =Y (oI G YA, Vo UF IR U o TAVZY 1§ VAo ) o] (o] ¢ Te [o 8 Boulde_ @ ll Aa l& Q ﬂ Name Adnaﬂﬂ. ca"“iv‘t Lab K — Glacial Topography in the Nederland Area For Lab K we will drive to Nederland to examine glacial landforms. Figure K-1 is a map of the field trip location. A series of questions will ask you to plot the location of each field trip stop on this map, S0 pay attention to the route the van takes as we near the field area. Stop 1 Our first stop is along the road to Lake Eldora ski area, at a prominent road cut with a granite knob to the right of the road. The valley below us is the valley of Middle Boulder Creek. This is the creek that is dammed by Barker Dam (which will be Stop 3). Some of the rocks we wish to examine lie in a road cut. Beware of traffic as you examine these rocks. The rest of our observations will be made from the top of the rock knob that lies just north of the road where the bus pulls off. Accessing this viewpoint will entail a short, steep hike that requires good shoes. Question L1: Locate the position of Stop 1 on the map of Fig. K-1. Plot its position using a small, neat dot labeled ‘Stop 1°. Question L2: Examine the road cut on the south side of the pavement. It consists of sediments deposited by a glacier. For this outcrop: a. Describe the degree of sorting of the particle sizes in this deposit. Estimate the approximate dimensions of the largest particle. What is the approximate size of the smallest material in the deposit (i.e. mud-sized, sand-sized, or bigger than sand-sized)? pao'\y fm ) 10in X L0 \n jJGV\'( SI'Z(DK . Describe the degree of rounding of the particles in the deposit (i.e. all well-rounded, all poorly rounded, some of each). oo\ c¢. This sediment forms part of a moraine deposited by the glacier that occupied this valley during the last glacial period, about 20,000 years ago. What type of moraine do you believe this was? Please explain your reasoning. Latud\ maGine "becuae ki aal(cl #e How o,’-"-!-(,-g lacier (on A fide). d. The rocks of a moraine crest usually lie at approximately the same elevation as that of the glacier surface. Using this rule of thumb and your Itation of the topographic map (Fig. K-1), what was the maximum glacier thickness at this point of the valley (in an east-west sense) 20,000 years ago when this moraine was deposited? Please show your work. T glacr ticnesy 1§ U0 §uek be (Ve Hehighot dwadien (S £, 400 minws fin lowest elevebon, cnichn 23 p,syo. o PRI N S VI VT R VET| L 53% @ ) Q [€7Ye] [oTe\ VAU (OO N IE:T o o] =Y (oI G YA, Vo UF IR U o TAVZY 1§ VAo ) o] (o] ¢ Te [o 8 Boulde_ @ ll Aa l& Q ﬂ Your instructor will now show you the short path up the bedrock knob that lies north of the road. To answer the next question, pay close attention to the topography of this knob as you hike up it. Question L3: Examine the topography of the bedrock knob on which you currently stand and that of the bedrock knob across the valley to the north. Also survey the general topography of the entire area and consult the topographic map of Fig. L1 in order to answer the following questions: a. In which compass direction did the glacier flow here in the Middle Boulder Creek valley (e.g. N60OE or N20W) 20,000 years ago? Your instructor has a compass that you can use to make this measurement. How did you make this . determination? . B . Loy onfn PPN b (grer (5 ov NE bo LW Cand virgveral . Treling Fov inérie di b Both the knob on which you stand and the knob directly across the valley are examples of what kind of glacial YOS crosional feature? Please explain what characteristics of the knobs and of the surrounding landscape you used to reach . this conclusion. ' TAT Un ¢ g U oF vOUr, N'A—w"fi‘ bt (e He Wrolor o't AdGes | and iF qocs from oot +ozep, Even though the last glacier to flow down this valley melted only about 15,000 years ago (a geologically short time in the past), very little glacially polished bedrock remains here. This is because the repeated freezing and thawing of water in cracks plucks small rocks off the outcrop regularly. Because the glacially polished rock surface is not much thicker than a sheet of paper, it doesn’t take much freeze-thaw action to pluck it off. Nevertheless, a couple of small patches of glacial polish do still remain on this bedrock knob. Locate this polish as you descend the knob. Question L4: Examine the glacially polished rock surface and answer the following questions: a. Compare and contrast the characteristics of the glacially polished rock surface with those of the unpolished surface (i.e. , those areas where freeze-thaw cycles plucked the polish off the rock). . - Glacial polirhs oy brovn amk Hunyatdes wireal Ha unw? red ey e bludih tndtn majoy oF b. Look for any glacial striations on the polished surface. In which two possible compass directions must the glacier have 4t = (e . flowed in order to form these grooves (use the compass)? U gk ks U FE o NB 4 o ise Semay | ot c. Draw a sketch of the glacially polished rock surface. Be sure to include a scale bar A a4 iewi our sketch has a sense of the area you are depicting. fi ™ 100

2:25 PM Mon Mar 1 L 53% @ ) Q [€7Ye] [oTe\ VAU (OO N IE:T o o] =Y (oI G YA, Vo UF IR U o TAVZY 1§ VAo ) o] (o] ¢ Te [o 8 Boulde_ @ ll Aa l& Q ﬂ 2:25 PM Mon Mar 1 d. Does the direction of glacier flow you obtained from these striations match the direction of flow you determined on other \1 “1 grounds in Question L3a? Compare the two answers. L ) W kiredion of glacier Fow mattres Mok frem ansvwr L3 a. Stop 2 The van will pull to the side of the road near Nederland High School for you to view the landforms at Stop 2. You won’t need to leave the bus for this stop. Question L5: Locate the position of Stop 2 on the map of Fig. K-1. Plot this position using a small, neat dot labeled ‘Stop 2’. Question L6: Locate the low, rounded hill that lies north and east of the bus. Where the road cuts through this hill you get a good look at the material of which it is composed (you will see this material even better if you look carefully as the van passes through the road cut immediately after leaving Stop 2). From your examination of this hill and its constituent material: a. What kind of glacial feature do you believe this hill represents? Be as specific as possible in your identification. Explain the features that led you to this conclusion. TUmi A VgL YUUIC Tk deporit if perpordidor R e f{ow of-thogladior topp jaghic b. Sketch the hill. Include on your sketch a scale bar. /—\ / '.mau -1 imqgonalf,(mf)/__\bj &, a0 f+ lc c. Locate this hill on the topographic map of Fig. K-1. Circle it on the map and label it ‘Hill at Stop 2’. o d. What is the elevation of the valley floor at the base of this hill (Use Fig K-1)? 6\ 100 sshunc behren oo lvner < o 360 £y, e. This feature was formed by the glacier that descended the Valley out 20,000 years ago (the last glacier to do so). Given your identification of the feature type in part a), what was the significance of this elevation from the standpoint of glaciation 20,000 years ago? Please explain your answer. Ouv w7 whtredtrvming of At 9rer (%,%0° D Stop 3 Stop 3 is an optional stop that lies at the junction of Colorado Highway 72 (the Peak-to-Peak Highway) and Magnolia Road. Due to time constraints, your instructor may or may not stop here. Even if you don’t stop, please answer Questions 8c, 9¢, 10c, and 11. If your class does stop, from where the van parks, walk up a small rise adjacent to the highway to obtain a panoramic view of the mountains west of Nederland. The peaks you see on the skyline here form part of the ‘Continental Divide’. 101 d. Does the direction of glacier flow you obtained from these striations match the direction of flow you determined on other \1 “1 grounds in Question L3a? Compare the two answers. L s d‘ Wion of glocier Flow mad-Ures Mok frem ansiver L3 a. The van will pull to the side of the road near Nederland High School for you to view the landforms at Stop 2. You won’t need to leave the bus for this stop. Question L5: Locate the position of Stop 2 on the map of Fig. K-1. Plot this position using a small, neat dot labeled ‘Stop 2’. Question L6: Locate the low, rounded hill that lies north and east of the bus. Where the road cuts through this hill you get a good look at the material of which it is composed (you will see this material even better if you look carefully as the van passes through the road cut immediately after leaving Stop 2). From your examination of this hill and its constituent material: a. What kind of glacial feature do you believe this hill represents? Be as specific as possible in your identification. Explain the features that led you to this conclusion. N TUm M| vadine Yae by deperit i P"Y"“‘“M" M flow of-trflador , topp jaghi b. Sketch the hill. Include on your sketch a scale bar. £ /—\ / '.mau | .mqgona!f,(m(), j &, ao lc- c. Locate this hill on the topographic map of Fig. K-1. Circle it on the map and label it ‘Hill at Stop 2’. d. What is the elevation of the valley floor at the base of this hill (Use Fig K-1)? QW Athun behen oo ner = Yo '% _c,k e. This feature was formed by the glacier that descended the Valley out 20,000 years ago (the last glacier to do so). Given your identification of the feature type in part a), what was the significance of this elevation from the standpoint of glaciation 20,000 years ago? Please explain your answer. Ouv w7 whtredtrvming of At 9rer (%,%0° D Stop 3 Stop 3 is an optional stop that lies at the junction of Colorado Highway 72 (the Peak-to-Peak Highway) and Magnolia Road. Due to time constraints, your instructor may or may not stop here. Even if you don’t stop, please answer Questions 8c, 9¢, 10c, and 11. If your class does stop, from where the van parks, walk up a small rise adjacent to the highway to obtain a panoramic view of the mountains west of Nederland. The peaks you see on the skyline here form part of the ‘Continental Divide’. 101 L 53% @ ) Q [€7Ye] [oTe\ VAU (OO N IE:T o o] =Y (oI G YA, Vo UF IR U o TAVZY 1§ VAo ) o] (o] ¢ Te [o 8 Boulde_ @ ll Aa l& Q ﬂ

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