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2005 Geology Higher Finalised Marking Instructions These Marking Instructions have been prepared by Examination Teams for use by SQA Appointed Markers when marking External Course Assessments. DO NOT WRITE IN THIS MARGIN SECTION A All questions in this section should be attempted. Forty marks are allocated to this section. 1. (a) Marks Figure Q1(a) shows the atomic structures of quartz and biotite mica. Figure Q1(a) Quartz Biotite mica Key tetrahedron of silicon and oxygen (SiO4) potassium ion hydroxide ion iron or magnesium ion Using diagram Figure Q1(a), explain the following. (i) Quartz has no cleavage. No planes of weakness OR ........................................................................................................................... the arrangement of SiO tetrahedra gives equal strength 4 ........................................................................................................................... in all directions ........................................................................................................................... 1 (ii) Biotite mica has very good cleavage in one direction. Planes of weakness run parallel to the sheets of SiO 4 ........................................................................................................................... tetrahedra ........................................................................................................................... ........................................................................................................................... 1 (iii) Biotite mica is denser than quartz. Biotite contains iron. Its high atomic mass would confer a ........................................................................................................................... high density on the mineral. OR The atoms in biotite are more closely packed than in quartz. Page two 1 (continued) (b) Figure Q1(b) shows the radii and charges of some metal ions. Marks Figure Q1(b) 150 140 potassium K+ 130 120 110 100 Ionic radius (picometres) 1. DO NOT WRITE IN THIS MARGIN calcium Ca2+ sodium Na+ 90 80 iron Fe2+ 70 nickel Ni2+ magnesium Mg2+ 60 50 aluminium Al3+ 40 30 20 10 0 1 2 3 Positive charge Use the information in Figure Q1(b) to explain the following observations. (i) In sodium plagioclase, (NaAlSi3O8), calcium (Ca2+) can completely replace sodium (Na+). Calcium ions are the same size as sodium ions. This allows ........................................................................................................................... them to replace each other. ........................................................................................................................... ........................................................................................................................... 1 (ii) Ores of nickel may form from weathered rock rich in olivine (MgFe)2SiO4. 1 mark 1 mark 2+ The nickel ion has the same size and/or charge as Mg and ........................................................................................................................... 2+ 2+ Fe . Thus Ni replaces these ions in olivine. On ........................................................................................................................... weathering, the Ni remains in the weathered residue. ........................................................................................................................... Page three 1 DO NOT WRITE IN THIS MARGIN 2. Marks Figure Q2 is a map showing an ancient sedimentary basin and surrounding deposits. Figure Q2 deltaic deposits N desert sandstones 5 6 4 3 r nta e im sed 2 n asi b y 1 50 km marine shales (a) Table Q2(a) shows the numbers of species of animal fossils collected at positions 1–6 on the map Figure Q2. Table Q2(a) Type of animal fossil Numbers of species at positions 1–6 Position 1 Position 2 Position 3 Position 4 Position 5 Position 6 Ammonites 10 4 2 0 0 0 Bivalves 92 34 15 4 2 0 196 77 22 20 22 10 75 55 30 22 6 0 Crustaceans Fish (i) Give one reason to explain why the numbers of species of animal fossils change from position 1 to position 5. Decrease in number of species because salinity decreases 1 → 5. ........................................................................................................................... OR Fewer species can exist in brackish water than in water of ........................................................................................................................... normal marine salinity. Accept increasing sediment in water. ........................................................................................................................... Accept increasing turbidity in water. Page four 1 DO NOT WRITE IN THIS MARGIN 2. Marks (a) (continued) (ii) Why does position 6 have the lowest number and variety of animal fossils? The water here would be hypersaline. Few species can survive in such conditions. OR Evaporation of water from this basin would make the water ........................................................................................................................... ........................................................................................................................... very salty. Few species can live in very salty water. ........................................................................................................................... 1 Accept basin empty at low tide. (iii) Fossils of ferns are found only at positions 4 and 5. Give one reason for this observation. Ferns are land plants. They have been washed into the ........................................................................................................................... sedimentary basin by the river which left the deltaic deposits. ........................................................................................................................... ........................................................................................................................... (b) 1 Which two of the following statements are correct? A The greatest percentage change in number of species between positions 1 and 3 is shown by the bivalves. B Bivalves are restricted to only a few habitats because they cannot swim. C The greatest percentage change in number of species between positions 1 and 3 is shown by the crustaceans. D Fish are found in the widest range of habitats because they can swim. E Crustaceans are the animals which can live in the widest range of habitats. F The greatest percentage change in number of species between positions 1 and 3 is shown by the ammonites. C E Give only the letters: ................... and ................... % change = difference × 100 number at position 1 Page five 2 DO NOT WRITE IN THIS MARGIN 3. Marks Figure Q3 shows a section through the oceanic crust and upper mantle. Figure Q3 A sea level D B E diorite magma C granite magma oceanic crust mantle (a) Complete Table Q3(a) to match the types of extrusive igneous activity with the positions marked by the letters A, B, C, D or E. Table Q3(a) Type of extrusive activity Position (Give one of A, B, C, D or E) Eruption of basaltic lavas not forming pillow lavas B Eruption of rhyolites and ignimbrites E Eruption of basalt forming pillow lavas C Eruption of andesitic lavas D or A 2 Any two for 1 mark (b) Describe the process by which basaltic magma is formed. Pressure reduction on peridotite 1 mark ................................................................................................................................... causes partial melting. Partial melt is basaltic magma 1 mark ................................................................................................................................... ................................................................................................................................... Page six 2 DO NOT WRITE IN THIS MARGIN 3. Marks (continued) (c) Using diagrams, explain why the oceanic crust on Figure Q3 has areas of normal and reversed magnetism. Diagrams 1 mark Basaltic magma erupted at oceanic ridges cools and acquires the prevailing magnetic field 1 mark Since Earth’s field changes basalt erupted at different times may have normal or reversed magnetisation 1 mark oceanic ridge normal magnetisation ⇒ field reverses ⇒ normal magnetisation reversed magnetisation field reverses Stripes of normal and reversed magnetisation parallel to ridge 3 Page seven 4. DO NOT WRITE IN THIS MARGIN Figure Q4 shows an ancient ocean environment. Marks Figure Q4 reptile sea ammonite crinoid bivalve sea floor (a) Which animal in Figure Q4 would provide the best zone fossil? Give a reason for your answer. Ammonite Answer ....................................................................................................................... Free swimming and in large numbers would thus be Reason ....................................................................................................................... common in sediment deposited over a wide area. ................................................................................................................................... ................................................................................................................................... (b) 2 In the geological timescale, how does a period differ from an era? An era is divided into periods OR ................................................................................................................................... Eras are longer than periods ................................................................................................................................... ................................................................................................................................... (c) 1 Explain the difference between relative and radiometric dating. Relative dating: putting events in order using cross-cutting and ................................................................................................................................... superposed relationships Radiometric dating: using radioactive elements to date a rock, ................................................................................................................................... mineral or organic material in years ................................................................................................................................... (d) 1 Why is it difficult to date sedimentary rocks using radiometric dating techniques? Do not often contain a radioactive mineral formed at the same ................................................................................................................................... time as the rock OR Sourced from rocks of various ages OR Consist of minerals, eg quartz, calcite, clay, which have no ................................................................................................................................... radioactive elements. ................................................................................................................................... Page eight 1 DO NOT WRITE IN THIS MARGIN Marks 5. Figure Q5 shows the results of research on a sample of fossil brachiopods of the same species. Figure Q5 100 75 Percentage of surviving brachiopods 50 25 0 5 10 15 20 25 Age of brachiopods (years) (a) Describe the general relationship shown by graph Figure Q5. Death rate very high among young brachiopods. After the age of ................................................................................................................................... four, death rate much less. OR 87.5% die by the age of five. From 5–25 the remaining 12.5% die ................................................................................................................................... off slowly. ................................................................................................................................... (b) 1 Do the brachiopods shown in graph Figure Q5 represent a life or death assemblage of fossils? Give one reason for your answer. Life assemblage Answer ....................................................................................................................... Reason has to be valid—even if weak All ages fossilised so has to be a life assemblage OR Only a Reason ....................................................................................................................... life assemblage would give a smooth, continuous curve OR This form of curve is shown by present-day populations ................................................................................................................................... (c) 1 In graph Figure Q5, in obtaining the age of the brachiopods, the scientist assumed that the ages of the brachiopods are proportional to their lengths. Give one reason why this might not be true. Better fed, disease free young brachiopods may be bigger than ................................................................................................................................... poorly fed, diseased old brachiopods OR In preset-day populations, age plotted against length gives a ................................................................................................................................... spread of points. Thus, there is no absolute relationship between age and length. ................................................................................................................................... Page nine 1 DO NOT WRITE IN THIS MARGIN 6. (a) The graph Figure Q6, shows the total volume of lava from Etna produced during the last 200 years. Marks Figure Q6 2000 1500 Total volume of lava erupted since 1800 (millions of cubic metres) 1000 500 0 1800 1850 1900 1950 2000 Year (i) Describe the trends shown by the graph from 1800 to 2000. 1800–1950: lava erupted at a moderate but constant rate. ........................................................................................................................... 1950–2000: rate of eruption speeded up. Lava erupted at high constant rate. OR ........................................................................................................................... At 1950 rate changed from 5.5 x 106 m3 yr–1 to 23.5 x 106 m3 yr–1 ........................................................................................................................... (ii) 2 What volume of lava was produced each year between 1900 and 1950? . 6 3 5 5 x 10 m ........................................................................................................................... Space for working 1950 Total vol = 825 x 106 m3 1900 Total vol = 550 x 106 m3 Volume produced in 50 years = 275 x 106 m3 Volume per year = 275 x 106 m3 50 years = 5.5 x 106 m3 yr–1 Page ten 2 DO NOT WRITE IN THIS MARGIN 6. Marks (continued) (b) Etna has a shape which is nearly conical. equation. The volume of a cone is given by this Volume = 1 × 3 ⋅14 × (radius of the base) 2 × height 3 Etna is 3 km high and the radius of its base is 10.6 km. Calculate the volume of Etna. 352.5 km3 Accept 352.8 km3 ................................................................................................................................... 1 Space for working V = 1 × 3 ⋅14 × (10 .×6) 2 × 3 km 3 3 (c) (i) Since records began in 1800, Etna has been producing, on average, 0.008 km3 of lava per year. Use this figure to calculate the age of Etna. 44057 years Accept 44 100 years ........................................................................................................................... 1 Space for working . 6) 2 × 3 km 3= 352 .⋅4575896 km 3 V = 1 × 3 ⋅14 × (10 × 3 Divide by 0.008 km3 yr–1 gives age = 44057.2 years (ii) Give two reasons to explain why this may not be the true age of Etna. • The shape of Etna is not exactly conical so its volume is not exactly known. • Using an estimated volume can not give an exact age ........................................................................................................................... Reason 1 ............................................................................................................. • The average rate of lava production may have been Reason 2 ............................................................................................................. more or less than the figure given from 1800 • The rate of 0.008 km3 is an estimate. The average ........................................................................................................................... rate may have been more or less since 1800. Page eleven 2 DO NOT WRITE IN THIS MARGIN 7. Figure Q7 is a field sketch of a rock exposure taken from a geology student’s fieldwork book. Marks Figure Q7 greywacke fossil soil zone of vesicles andesite lava sandstone metamorphic rock A zone rich in chromite and olivine mudstone with worm burrows sill of basic igneous rock metamorphic rock B (a) Give three pieces of evidence suggesting that all the rocks below the lava are the wrong way up? Worm burrows 1 Answer .................................................................................................................... n Here, they are -shaped. When formed they would be Reason .................................................................................................................... U U-shaped. Thus, they have been inverted. ............................................................................................................................... Chromite-olivine layer in sill 2 Answer .................................................................................................................... These are early-formed dense minerals which would Reason .................................................................................................................... sink to the base of an intrusion. Here, they are at the top so the sill has been inverted. ............................................................................................................................... Cross-bedding in sandstone 3 Answer .................................................................................................................... When deposited the layering would be concave Reason .................................................................................................................... upwards . Here, the layers are concave ............................................................................................................................... downwards so they have been inverted. Accept grain, firming in the wrong direction Page twelve 3 DO NOT WRITE IN THIS MARGIN Marks 7. (continued) (b) (i) Name metamorphic rock A. Metaquartzite OR quartzite ........................................................................................................................... (ii) Name metamorphic rock B. Hornfels ........................................................................................................................... (c) 2 Give two reasons to explain how the student would have known that the andesite was a lava flow and not an intrusion. • The underlying sandstone has not been metamorphosed. Reason 1 ...................................................................................................................... Also, the overlying rock has not been metamorphosed. A sill would have metamorphosed rocks below and .................................................................................................................................... above. .................................................................................................................................... • There is a zone of vesicles at the top of the andesite. Reason 2 ...................................................................................................................... Gas escapes easily from lava so vesicles are characteristic of lava flows .................................................................................................................................... • There is a fossil soil on top of the andesite. A sill would not be exposed to the atmosphere so the andesite forms .................................................................................................................................... a lava flow. • The top of the andesite is very uneven. Lava flows tend to be rubbly and uneven. Sills tend to have more even tops. Section A: Total (40) marks • The andesite does not transgress into the rocks above and below. A sill would possibly do this. Page thirteen 2 DO NOT WRITE IN THIS MARGIN SECTION B This section consists of three questions. Only ONE question should be attempted. Fifteen marks are allocated to this section. Marks Candidates should write their answer on pages 15, 16 and 17. Additional space for answers may be found at the end of this book. Credit will be given for the use of maps and diagrams. 8. 9. Write an essay on Earth physics. Give details as follows. (a) The types and properties of earthquake waves 3 (b) The use of earthquake waves in working out the internal structure of the earth 5 (c) The origin and properties of the Earth’s magnetic field 4 (d) The origins of the Earth’s internal heat Write an essay on the formation of ores by surface processes. Give details as follows. (a) Placer deposits 3 (b) Residual deposits 4 (c) Deposits of iron ore formed in: (i) Precambrian times (ii) post Cambrian times 4 (d) 10. 3 (15) Deposits formed by secondary enrichment 4 (15) Write an essay on sedimentary rocks. Give details as follows. (a) The formation and classification of sedimentary rocks 6 (b) The formation of sedimentary structures 5 (c) The environments in which non-marine sediments are deposited 4 (15) Section B: Total (15) marks Page fourteen DO NOT WRITE IN THIS MARGIN SPACE FOR ANSWERS 8. (a) Properties of P, S and L waves. 1 mark each (b) Changes in speed; reflection; refraction. Crust, Moho, lithosphere, asthenosphere (LVZ), mantle, outer core, inner core 10 points, ½ mark each (c) Properties: dipole and non-dipole fields, magnetic poles, reversals, changes in strength 4 points, ½ mark each Origin: electric currents in outer core. Currents flow generally →E). Changes in strength and parallel to lines of latitude (W→ direction of currents cause similar changes in magnetic field. 2 points, 1 mark each 9. (d) Decay of radioactive isotopes; heat remaining from origin (KE of impacting asteroids and mini planets); gravitational energy from core formation; slowing of rotation. 3 sources, 1 mark each (a) Placers—water and wind; locations; properties of minerals 6 points, ½ mark each (b) Residual—formed in situ; chemical weathering; formation of Al and Ni deposits 8 points, ½ mark each (c) Iron Ores (i) Precambrian—BIFs; atmosphere reducing; Fe2+ carried in solution; precipitated by blue-green bacteria 4 points, 1 mark each (max: 2 marks) (ii) Post Cambrian—limonitic bog iron ore formed in swamps; siderite nodules and bands in Carboniferous rocks; Jurassic volitic ironstones (chamosite + siderite). 4 points, 1 mark each (max: 2 marks) (d) Secondary enrichment: chemical weathering of chalcopyrite vein. Cu2+ carried down to water table. Above water table Cu + CO2 → carbonates. Below water table Cu displaces Fe from chalcopyrite so copper ore enriched. 4 points, 1 mark each Page fifteen DO NOT WRITE IN THIS MARGIN SPACE FOR ANSWERS 10. (a) Biological: eg coal, coral limestone Chemical: eg evaporites, some limestones Detrital: eg conglomerate, breccia, sandstones, siltstone, mudstone. 12 points, ½ mark each (b) Descriptions of 5 structures 1 mark each (c) Descriptions of 4 environments 1 mark each Page sixteen DO NOT WRITE IN THIS MARGIN SPACE FOR ANSWERS Page seventeen DO NOT WRITE IN THIS MARGIN SECTION C All questions in this section should be attempted. section. 11. Forty marks are allocated to this Marks Look at photograph Q11 below. Photograph Q11 (An aerial view of a desert landscape) A Road (a) Identify geological feature A. Alluvial fan ................................................................................................................................... (b) 1 Using diagrams, explain how this feature was formed. Flash flood produces sediment-laden stream which changes speed on running from canyon onto flat valley floor. Distributaries deposit sediment in fan shape. coarse-grained sediment fine-grained sediment Layering from repeated flash floods Explanation 1 mark Diagrams 1 mark sediment becomes finer towards fan margin 2 Page eighteen DO NOT WRITE IN THIS MARGIN 12. Marks Look at photograph Q12 below. Photograph Q12 All exposure of volcanic ash 0 10 cm (a) Identify the geological feature shown in Photograph Q12. Volcanic (breadcrust) bomb, pyroclast, lava bomb ................................................................................................................................... (b) 1 Using diagrams, explain how this feature was formed. A mass of liquid but viscous lava thrown from a volcano acquires a round shape in flight. On cooling, the bomb forms a hard skin. On further cooling the hard skin is broken and pushed apart by expansion of the bomb interior. Expansion caused by release of gas and formation of vesicles. Explanation 1 mark Accept origin of pyroclastic material Diagrams 1 mark for explanation 1 mark lava rounds off in flight solid hard skin forms as bomb cools inside expands as gas released liquid bomb vesicles volcano solid skin broken and spread ash Page nineteen 2 DO NOT WRITE IN THIS MARGIN 13. Study the map Figure Q13 on the separate worksheet and answer the questions based on it. (a) (i) How many unconformities are shown? Two ........................................................................................................................... (ii) 1 In which direction does the fold plunge? South ........................................................................................................................... (b) Marks 1 On which side of fault F1 have the rocks moved up? Give a reason for your answer. West Answer ....................................................................................................................... Gneiss abuts on younger sedimentary rocks so west side Reason ....................................................................................................................... must have moved up ................................................................................................................................... (c) 2 Which statement is correct? A Both F1 and F2 are normal faults. B F2 is a normal fault; F1 is a reverse fault. C Both F1 and F2 are thrust faults. D F2 is a reverse fault; F1 is a normal fault. E Both F1 and F2 are reverse faults. D Give only the letter: .................... 1 Error on map Felsite should cut breccia Page twenty Page twenty-one X F1 F2 shale siltstone F1 - 1 mark F2 - 1 mark anticline - 1 mark breccia and arkose - 1 mark relationships under - 1 mark breccia arkose breccia conglomerate Figure Q13(e) felsite dolerite metamorphosed dolerite gneiss Key (Rocks not in order of age) fault with dip of fault plane in degrees directions of strike and dip 30 with dip in degrees F1 55 P Y Position P: Junction between dolerite and metamorphosed dolerite dolerite metamorphosed dolerite DO NOT WRITE IN THIS MARGIN Marks 13. (continued) (d) Figure Q13(d) shows a junction between dolerite and metamorphosed dolerite at position P on the map Figure Q13. Figure Q13(d) dolerite metamorphosed dolerite mineral C 3 mm mineral A (i) mineral B junction Name minerals A, B and C. pyroxene Mineral A ............................................................... plagioclase Mineral B ............................................................... amphibole or hornblende Mineral C ............................................................... (ii) 3 Explain why the metamorphosed dolerite shows no foliation close to the dolerite. Gneissose metamorphosed dolerite has been subjected to .......................................................................................................................... contact metamorphism by dolerite. Contact metamorphism .......................................................................................................................... (e) takes place under hydrostatic pressure so foliation destroyed. .......................................................................................................................... 1 On the topographic profile Figure Q13(e) (on the separate worksheet), draw a geological section between points X and Y on the map Figure Q13. 5 Page twenty-two DO NOT WRITE IN THIS MARGIN Marks 13. (continued) (f) Write a geological history of the area shown on the map, Figure Q13. Rock of unknown type intruded by dolerite Regional metamorphism then intrusion of dolerite Uplift, erosion Deposition of conglomerate, siltstone, shale above unconformity } 1 mark } 1 mark Folding 1 mark Uplift, erosion Deposition of breccia and arkose above unconformity } 1 mark Faulting 1 mark Intrusion of felsite 1 mark 6 Page twenty-three DO NOT WRITE IN THIS MARGIN Marks On the map Figure Q14, a thin coal seam of uniform dip outcrops at A, B and C. Figure Q14 600 m 60 0 40 0 C 0 400 m 40 300 m 0 B 200 m 0 30 0 20 N 500 m 50 30 0 100 m 100 0 20 A 500 m Key 0 C 10 14. outcrop of coal seam surface contour with height in metres (a) Draw structure contours for the coal seam onto the map Figure Q14. 2 (b) Draw in the outcrop of the coal seam onto the map Figure Q14. 2 (c) Calculate the angle and direction of dip of the coal seam. 30–35 ° Angle ................... south Direction of dip ................... 2 Space for working 500 m ≡ 34.3 mm 10.8 mm ≡ 500 x 157.43 32.4 ° 10.8 34.3 ≡ 157.43 m 100 10mm 145.77 34.45 ° Page twenty-four 15. Study the map Figure Q15 and answer the questions based on it. Figure Q15 500 600 700 800 900 1000 1100 900 N 800 800 700 600 600 700 800 300 600 600 L 900 1000 900 800 700 600 500 400 0 90 N 100 700 500 0 80 M 70 500 700 0 1000 1000 900 900 800 800 700 700 600 600 500 500 400 400 60 0 50 0 700 800 Key 400 500 600 700 800 surface contour with height in metres 00 50 0 600 900 0 8 1000 200 400 metres borehole L 300 borehole with depth to coal seam in metres 500 500 structure contour for fault plane with height in metres depth from surface to coal seam Page twenty-five DO NOT WRITE IN THIS MARGIN 15. Marks (continued) (a) (b) Structure contours have been drawn for a fault of uniform dip. Draw in the outcrop of the fault plane. 2 A thin coal seam of uniform dip is found in boreholes L, M and N at the depths shown from the surface. (i) Draw structure contours for the coal seam over the whole area of the map. Number the structure contours north of the fault. 3 (ii) Draw in the outcrop of the coal seam on the north side of the fault. 1 (iii) On the south side of the fault, the coal seam is 100 m lower than it is on the north side of the fault. Number the structure contours on the south side of the fault. 1 (iv) Draw in the outcrop of the coal seam on the south side of the fault. 1 Section C: Total (40) marks [END OF MARKING INSTRUCTIONS] Page twenty-six