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Names:________________ & _________________ Circle Section: 1=Wed or 2=Thurs GEOS 100 Lab 1 - Based on AGI manual 9th edition Observing and Measuring Earth Materials and Processes This lab is worth ~2% of the course total. Use and hand in this lab handout and do not tear pages from your lab manual to preserve it for later use. Work in pairs (or in larger groups for some of the “experiments” ) and hand in one lab for each pair, by the beginning of the following lab period. The written part of the lab is based on the lab manual. In addition, familiarize yourself with F300, the maps and diagrams on the walls, and minerals and rock specimens. These are the materials that you will be dealing with during the course (and the rest of your life). You will become aware of the geology of western Canada and how the rocks and processes around Victoria are related to larger scale processes over space and time. Turn to Lab 1 of the lab manual and work your way through the readings and exercises. Answer the questions from the manual in the corresponding spaces provided. Activity 1-Nought: Observing Earth Materials and Testing Hypotheses 1. Read p 8-9 and examine specimens of Chalcopyrite. How do you determine if this is a pure substance (elements cannot be chemically separated into simpler substances). Chalcopyrite is a pure element. True / False. Why? _________________________________________________________ 2. Chalcopyrite is a compound. True / False. What elements does it contain and why for each element? A.element_________why_________________________________________ B.element_________ why_________________________________________ C.element__________why__________________________________________ Activity 1.1 Basketball Model of Earth Label in the correct relative position the spheres of the Earth on the following page using the scale provided, wherein the position of the Inner Core at 1196 km is represented by a circle at 22.3 mm radius. The ratio (scale factor) of km in the real Earth per mm in your diagram is given by 6371 km per 119 mm. 1. Write the numerical value of this ratio here after converting both numbers to meters:__________ m/m (2 points) 2. What is the fractional value of each radius in the table, if the basketball’s radius is 1.00 for the top of the Crust? If you do this correctly, the top of the crust should be the surface of the basketball and the ocean and atmosphere sit above that. (10 points) 1 Hint: the thickness of each layer is the difference between it’s top and it’s base. The fractional radius needs to count the total thickness of all layers below that level. We want the top of the crust to be the total radius, the oceans and atmosphere sit above that >1.000 Sphere Atmosphere Hydrosphere Crust UM Lithosphere UM Asthenosphere Lower Mantle Outer Core Inner Core Distance to top/base (km) Thickness of layer Fraction of Earth Radius 97.2 0 3.79 35 35 1.000 100 650 2890 5150 6378 1228 0.193 2 Activity 1.2: Remote Sensing and Exploring the Earth for Copper A. Read about MODIS on p.10-11 and Fig 1.8 then analyse Figure 1.9 on p 12.of the photo and MODIS image of Mt. Etna. 1. How many volcanic vents (A) are active in the Oct.30, 2002 photo of Mt.Etna as taken from the space station? # of.vents:_________and what types of materials are present in the plume? ___________and ___________. How can you tell? ________________ (4) 2. How far has the plume travelled in the MODIS image of Oct 28, 2002? ________km From the trajectory and location of the plume, where ash particles form deposits? _____________________________ and __________________________________ (3). 3. From the images, how did this eruption affect the atmosphere:_________________________________________________________ and hydrosphere?___________________________________________________________. B. Analyse figure 1.10 using the information in figure 1.8 and p 10-11. Bear in mind that the images do not directly sense Cu, Ag or Au, but just the response of the soils and their minerals to the bands being detected. 1. Examine figure 1.13 showing ASTER images of Chile’s Escondida open pit copper mines. Choose the best location for a new open pit from A, B or C _____________ and explain your choice. _____________________________________________________ ______________________________________________________________________ 2. Suggest a scientific approach or program of activities to test this recommendation? _____________________________________________________________________ _____________________________________________________________________ Activity 1.3: Measuring Earth Materials and relationships (use the units and charts for conversions on p. x & xi) A. converted units: (6 points) 1. 10 mi. = _______ kilometres 2. 1 ft. = _______ metres 3. 16 km = _______ metres 4. 25 m = _______ centimetres 5. 25.4 mL = _______ cm3 6. 1.3 L = _______ cm3 Draw (3) B. 1 cm line segment C. 1 cm2 square 3 D. 1 cm3 cube E. Work out a method, do the experiment, then explain in words how to measure the density of water using a graduated cylinder. Write a formula to succinctly summarize your method, giving your answer. The symbol for density is the greek letter rho. (4) The reference density for distilled water varies with temperature and atmospheric pressure. The measured values of these today are: T°C _______, P mm Hg ______, P atm ______ and Density from the CRC Handbook table = ___________. 1. Method:___________________________________________________________ __________________________________________________________________ __________________________________________________________________ 2. Calculate your own density for deionized water. Density is a derived unit of mass divided by volume. Show your calculations (3). 3. Compare your measured value to the expected value for water under lab conditions today. Express this as a % error given by: 100 x (Your value – True value) True value If your %error is greater than 5% find out what you did wrong and repeat your measurements. F. Determine the density of clay. Describe your method. clay = _______ g/cm3 Calculations: G. Review your work and conclusions from E and F above: 1. Why does the clay sink in water? (1) 2. Try to float the clay and describe or draw how this can be done. (2) 3. Explain the physics of how can the clay be made to float? (2) H. Compare the densities of Earth’s spheres to liquid water at S.T.P. (25°C, 1atm): (4) 1. Use the composition of air at 78% Nitrogen and 22% Oxygen and 1 mole of gas occupies 22.4 litres at STP and Air g/mol = (28 g/mol N2 x 0.78) + (32 g/mol O2 x 0.22) atmosphere = g/cm3 4 2. For the density of the lithosphere use the table on p.27 and the histogram on p.19 fig 1.14 to estimate the proportions of granitic and basaltic crust (4) lithosphere = (fraction of basalt area x basalt ) + (fraction of granite area x granite ) Weighted Average lithosphere = g/cm3 I. Complete the table for materials and densities for each of Earth’s “spheres” from the lab manual or from your calculations above (atmosphere, cryosphere, hydrosphere, lithosphere, mantle, core etc.) and explain why they occur in this order. Give 3 significant figures. (10) Sphere Atmosphere (N2 + O2 ) Hydrosphere Crust (Granite + Basalt) UM Lithosphere Lower Mantle Outer Core Inner Core Density (g/cm3) Material Air Seawater Peridotite Fe+Ni+…? Explanation for order: Activity 1.4 Density, Gravity, and Isostasy A.1. Sketch a wooden block labelling its dimensions and calculate its density. Recall Volume = (Length x Width x Height) (measure to nearest tenth of a centimetre). (4) A.2 Calculate the density of a wood block. = mass (g) / volume (cm3) (2) B. Sketch the wooden block measuring the location of the wetted line (plimsoll line on a boat). The total mass of the lighter wood block only displaces a volume of water equal to the wetted part. This demonstrates the principle of buoyancy. (3) 5 1. What is the total height or thickness? H(block) =__________cm 2. Measure the wetted part. H(below)=__________cm 3. Measure the remaining dry part. H(above)=__________cm C. Given that the portion of the wood block’s height (and mass) that is below the equilibrium line is equal to the total height of the wood block times the ratio of the density of wood to water, write an isostasy equation for height of wood below equilibrium line. (5) 1.) Hb = 2.) Use this equation and the measured values for your block’s density, height above and total height to predict the height below. Compare this calculated value to the actual measured value and express this as a %error for your calculated value compared to the real wet block. % Error = 100 X {calculated-real}/real = ______________ % D. Write an isostasy equation for height of wood above equilibrium line. While we can readily observe both the upper and lower parts of wood blocks, it is not so easy for icebergs (ask Captain Smith!) or mountain ranges (Ask Mr. Airy or Mr. Pratt!) (Hint: Htotal = Ha + Hb Do a substitution using the other heights & rearrange the equation in C-1 to solve for Ha .) (5) Ha = E. Using the density of sea ice as 0/.917 g/cm3 and that of sea water as 1.025 g/cm3, 1.) Repeat the Hb = height below calculation from part C, for the iceberg to predict what proportion of the iceberg is hidden below sea level. Compare this to the total height of the iceberg pictured in figure 1.13b and give your % error for Hb. (5) 6 2.) As for part 1, solve for Ha = the iceberg above water, using the equation from part D to predict what proportion of the iceberg shows above the water. Compare this to the total height of the iceberg pictured in figure 1.13b and give your % error Ha. (5) 3. Icebergs are not perfect blocks. Due to this irregular shape, the cross sectional area is probably a better estimate of mass and buoyancy than height alone. Repeat part 1 and 2 above but this time accurately count the squares and use cross sectional area instead of height. (count whole squares and fractional squares) (4) Area below = Area above = How do these results compare to the estimates from the heights alone? (4) For part a % error for Area below = ________ For part b % for Area above = _________ 4. Notice the tilted ledge above the waterline in figure 1.13b and discuss what will happen to the position of the old plimsoll line (waterline like on a boat) as the top of iceberg melts and why? (2) 5. Charles Dutton compared raised beaches along continental margins to that old tilted ledge on the iceberg photo. Compare eroded continents to melted icebergs. Many sections of coastlines have wave cut platforms that are considerably above modern sea level. According to Dutton p.26 and again on p 29 Activity 1.5-F, ancient shorelines have become elevated because… (2) 7 Activity 1.5: Isostasy and Earth’s Global Topography A. My basalt sample: mass _______ g , volume ______ basalt = _________g/cm3 (3) Average density of basalt (yours plus 9 in table p.27) =___________ g/cm3 (1) B. My granite sample: mass ______ g , volume ______ granite = _________ g/cm3 (3) Average density of granite =___________ g/cm3 (1) C. Isostasy calculations to explain Earth’s Topography (high continents and mountains versus low ocean basins and deep sea trenches) 1. For 5 km thick seafloor basaltic crust in mantle calculate: H basalt above = km (3) 2. For 30 km thick continental granite in mantle calculate: H granite above = km (3) 3. Net elevation difference Continental Crust above mantle minus Oceanic crust above mantle: (H granite above - H basalt above) = km or ____________ metres. (2) 4. How close are your calculated isostasy H above results compared to the actual topographic height differences between the average continental land elevation and average ocean basin depth in terms of distances __________ (metres) and percent errors __________ %. Assume the topographic averages to be the true value for this error calculation. (3) 5. What can you infer from this about the validity of our simple 3 rock Earth (only granite or basalt on peridotite) and 1 dimensional isostatic thickness model for calculating the outside shape of the Earth? (Basically, if your answers agree to a few %, this is a pretty reasonable simplification!) (2 points) 8 D. Reflect on your work using isostasy calculations to account for the observations either on land and sea or from space, to account for the observation that Earth has a bimodal global topography (2 predominant but different elevations; e.g. land and mountains are high and while seas are deep.) How valid is isostatic theory? What kind of rocks must underlie the land versus the sea? (3) E. Compare a mountain with the iceberg in figure 1.16 in terms of the changes that affect them, the driving forces which move them and the time scales for these changes and processes. How are these forces or agents of change, changes and time scales similar or different. (6) Force Change Time Iceberg Mountain F. Use the data provided in the manual p20-29 and your calculations, to make an inference concerning the Pratt (variable density) versus Airy (variable thickness) hypotheses for crustal elevation and isostasy’s driving forces. Which model best explains continents and continental mountain ranges? Which model best explains the elevation differences between mid ocean ridges and ocean basins? Is one model more right than the other or does the real Earth require that we understand and use both ideas to account for different features? Feel free to make and label your own sketches here. (4) 9