MS3£3.00

GENERAL CERTIFICATE OF EDUCATION TYSTYSGRIF ADDYSG GYFFREDINOL

MARKING SCHEME

GEOLOGY

SUMMER 2008

INTRODUCTION The marking schemes which follow were those used by WJEC for the Summer 2008 in GCE Geology they were finalised after detailed discussion at examiners' conferences by all the examiners involved in the assessment. The conferences were held shortly after the papers were taken so that reference could be made to the full range of candidates' responses, with photocopied scripts forming the basis of discussion. The aim of the conferences was to ensure that the marking schemes were interpreted and applied in the same way by all examiners. It is hoped that this information will be of assistance to centres but it is recognised at the same time that, without the benefit of participation in the examiners' conferences, teachers may have different views on certain matters of detail or interpretation. WJEC regrets that it cannot enter into any discussion or correspondence about these marking schemes.

1

GL1 1. (a) Two arrows both pointing West (2) [2] (b) (i) 0.1 - 4.9 million years (1) [2] Closer to the spreading centre than other points therefore younger (1) (ii) Radiometric dating, Rb/Sr, K/Ar (1) [2] Use of paleomagnetism/magnetic stripes (1) (c) (i) V shaped (in section) (1) 1 of these [2] Crescent shaped/curved (1) 16-50 km wide (1) 1 of these 360-480 km long (1) (ii) Partial melting (1) [2] of oceanic lithosphere/ basaltic/mafic plate (1) Contamination from silica-rich ocean sediment (1) (iii) Plate convergence (1) [4] Subduction (1) Friction (1) Stress release (1) Volcanic activity/rising or moving magma (1) R Detail on impact of moving magma (1) Credit other relevant points Total 14 marks

2

2. (a) (i) Quartz (1) [2] Feldspar/Plagioclase/Orthoclase (1) (ii) Size 0.05 - 1.25 mm (typically 0.6mm) or “medium” grain size (1) [2] Angular feldspar grains (1) 2 of these Rounded quartz grains (1) Poorly sorted (1) Credit other relevant descriptions (b) Dip towards the East (1) [2] Steeper dip in the West (1) 2 of these Or an angle quoted: accept range 10-40° (1) (c) (i) Likely to be true because: [2] Mineralogy is similar (1) Or Quartz and Feldspar most common mins in granite (2) Lack of mica noted (1) (ii) Arkose is cut by the granite (1) [4] Arkose is pushed steeper by the granite (1) Max Arkose is metamorphosed by the granite (1) 3 of these Granite contains fragments of the conglomerate (1) Granite is younger than the arkose (1) Granite younger than conglomerate (1) Conglomerate younger than arkose by superposition (1) (d) Credit up to 3 differences (3) [5]

Rock at X Shale at Y crystalline Granular/clastic coarser fine chiastolite/andalusite clay Porphyroblastic or equivalent Equigranular or equivalent Random orientation of minerals Parallel orientation of minerals/grains

Credit up to 2 of the following reason marks (2) Contact metamorphism (1) Heat from batholith (1) Recrystallisation (1) Chemical re-arrangement (1) Total 17 marks

3

3. (a) J = Stipe (1) [2] K = Theca (1) (b) Appearance: Late Cambrian - both correct for 1 mark [1] Extinction: Early Carboniferous (c) [3]

Property of a most graptolites Explanation Geographically widespread • Floated in the oceans

Easily identifiable • Varation in stipes and thecae Unique appearance

Usually poorly preserved • Fragile skeletons/easily broken/lack

of hard parts

(d) Genus A less valuable than Didymograptus R (1) [4] Genus A has longer time range (1) Allows less precise dating (1) Genus A fixed (not floating) (1) 4 of these Genus A less widespread (1) Maximum of 2 marks if the comparison is incorrect, or no comparison made. (e) Shale has fine grains (1) [3] Lower energy deposition (1) So graptolite less likely to be fragmented (1) Black = anoxic (1) Anoxic suggects less decay (1) Anoxic suggests fewer predators (1) Shale impermeable (1) Less oxygen or groundwater circulation (1) So less post-depositional breakdown(1) Pyritisation (1) Credit other relevant answers (f) Extinct or equivalent (1) [2] Cannot apply uniformitarianism or equivalent (1) Lack of soft parts (1) and consequent difficulties of interpretation (1) Total 15 marks

4

4. (a) Bed thickness = 80cm (credit 70-90cm) (1) [2] Silt size grains or “fine” (1) (b) (i) Bed 1 (1) [3] Base of sequence/law of superposition (1) Sequence right way up based on sole structure evidence (1) (ii) Bed 3 (1) [3] Coarser at base but finer at top/upward fining (1) Finer particles only deposited under lower energy conditions or decreasing energy or equivalent (1) (c) Named sedimentary structure (1) [6]

Location (1) Scale (1) Standard of drawing/description (2) (Maximum 4 of the above marks) Correct identification of environment of deposition (1)

Explanation of how sedimentary structure formed or why it indicates the particular environment of deposition. (2)

Total 14 marks

5

GL2a

1.

(a)

(i)

Composition – dark/black.mafic Texture – fine crystals

1 1

2 (ii) Lava surface

Cooling of lava surface Movement (of interior of flow) (Accept pillow lava formation max 2)

1 1 1

3

(b) (i) (only mark evidence if evaluation is correct) (Photo 2) True – they cross-cut Rock Unit A (Map 1) False – these are discordant intrusions so are not sills

1 1

2 (ii) e.g.

Baked or chilled margins – would be on both upper and lower surfaces of Rock Unit B if younger Included fragments – B would contain fragments of A if younger

1+1

1+1

2 (total 9)

2. (a) (i) Scale Shape e.g. elongate length 2x width, oval cross-section Detail e.g. vertical lines, horizontal lines

1 2 2

5 (ii) Mould/cast

Rotting/solution of tissues Infill by sediment (Accept e.g. carbonisation, replacement max 2)

1 1 1

3

(b) Credit any single test/observation which leads to the conclusion that the rock is cemented (clast rather than matrix support) or establishes the degree of cement. e.g. 1 use water/acid bottle (D) water/acid soaks in very slowly/quickly (E) pore spaces totally/partially infilled by cement 2 use of hand lens (D) the grains are well sorted (E) lithified by a cement rather than a matrix 3(D) rock crumbles (E) poorly cemented

(D) 1+1

(E) 1+1

4 (total 12)

6

3. (a) (i) Minerals - crystals (not clasts)

Grain size – medium (2-4 mm) to coarse (+5mm) Mineral arrangement – foliated (aligned) – minerals separated into bands

1 1 1 1

4 (ii) Gneiss 1

1 (iii) D – metamorphism

- high grade or regional Granite – melting – intrusion of magma or crystallisation on cooling

1 1 1 1

4 (b) (i) Horizontal line on eastern face of quarry

True dip of F is to the east, strike direction seen on N-S face 1 1

2 (ii) e.g. cross-cutting

e.g. different dips

1

1 (iii) e.g. sedimentary rock above regional metamorphic

– possibly a weathered and eroded surface? – a bored surface? – included fragments? – cross-cutting of granite vein

(D)1 (E)1

2 (total 14)

4. (a) (i) (accurate i.e. not drawn through unconformity for full credit) Draw (full N-S trace) and label to W of F1 Draw (N-S traces stop at unconformity) and label to E of F1 (Draw 3 but not labelled) (Draw and label 3, but one error)

1 1

1 max

1 max

2

(ii) Trend – north to south Symmetry – the dip of the limbs/ limb outcrop widths Wavelength – distance between crest-crest (trough-trough)

1 1 1

3 (b) (i) Rock Unit E Rock Unit G 1

1 (ii) 65o (60o – 70o) 1

1 (iii) E older than G therefore E moved up

E is on hanging wall, therefore reverse 1 1

2 (total 9)

7

5. (a) See section

11 (b) YOUNGEST

OLDEST

B A C F G E D

1 (B/A)

1 (C/F)

1 1

1 (G/D)

5 (total 16)

Fault F1

Alternative for Folding

8

B

plu

g

dyke

Faul

t F2

Fa

ult F

1

Fold

s

ynfo

rm

axi

s

Fold

a

ntifo

rm

sym

met

ric

a

xis

Bas

e F

Bas

e A

11 m

ax

9

GL3

1. (a) (i) Andesite, (intermediate or silica-rich (1) [1] (ii) Partial melting (1) of mafic (crust/mantle) material (1) Subduction(1) Convergent (destructive) plate margin (1) (2 max) (b) (i) [2]

Anjer

45-50-55 40 67.5-75-82.5 15

50 (1) 50/40=1.25(1) *60 = 75 km hr-1(1) [3] (ii) 20 minutes later at TB(1) - although nearer (1) Wave travelled faster (1) Deeper water to VH/land or islands in way to TB (R1) 2 descriptions and 1 explanation or visa versa (3 max) [3] (iii) At TB Shape of coast causing funnelling (1) Shallower shore - waves slow more and rise higher (1). [2] (c) Early warning system, monitoring/predicting volcano, Any coastal defence methods explained Development free zone, buildings at 90 to coast, Buildings on piles/lower floor free from development, walls/embankments/raised coastal roads etc. (2 max) [2] Total 13 marks

10

2. (a) Density difference (1) [1] (b) (i) abstraction is locally faster (1)

than recharge through rock can replenish -RATE (R1) [2]

(ii) 60m [1] (iii) The sketch to show that the depth of the boundary is ~60m below sea

level(1) Conforming roughly to the cone of depression (1) [2]

(c) (i) Permeable (1) - Joints/faults (1) Bedding planes (1), pores connected (1)

(2 marks max) [2]

(ii) Saline incursion/contamination Local exhaustion of supply

Borehole A could interfere with abstraction from other boreholes if cone of depression overlaps

(Any 2 or one explained well) (2 marks max) [2]

(d) Holistic: Reduction of pore water pressure Compaction/readjustment/repacking of sediment Reduces pore space/rock volume Surface subsidence.

(2 marks max) [2]

Total 12 marks

11

3. (a) Describe how the mechanisms and triggers of mass movement (e.g.rock avalanches, landslides and debris flows) are linked to natural processes and rock properties. [15]

Holistic expect:

angle of slope Slopes above 35 degrees are often unstable (exceptions – when saturated – solifluction). Friction is greater than forces of gravity – when reduced mass movement occurs. Rock slides/falls, rotational slip, slumping, debris flows. lithology/weathering Competent rock (granite) is reduced to clay minerals – loses cohesion between grains/along joints. Shale, clay etc. are incompetent and will flow/slip under load pressure and lubrication – rotational slip. groundwater/rainfall As pore pressure increases, reduction of friction between blocks and particles results mass movement. Also ground vibration (earthquake),

shrinkage, expansion(clay), loading(volcanic collapse, undercutting by river/sea).

(b) Explain how slopes prone to mass movements might be stabilised. [10]

Reprofile to below the stable angle (approx. 35 degrees depending on other factors)

Drainage control – drains, pipes etc to remove surface water to improve cohesion. Planting trees – reduces interception, removes water and roots bind the soil. Engineering structures:- Gabions, retaining walls, shotcrete, rock bolts etc. Prevention of instability caused by human activity. Other sensible specifically related to case studies. Credit for examples (Max 10 marks)

Total 25 marks

12

4. (a) Describe the factors you would investigate to assess the suitability of a potential landfill site for the disposal of domestic waste. [15]

Investigations Porosity/permeability experiments Groundwater flow Need for artificial liners Physical and chemical stability of site Techniques used to achieve these: Resistivity, groundwater monitoring, borehole/auger, mapping etc.

(b) Explain why former landfill sites may pose problems for future development

of the area [10]

Problems Waste subsidence Methane – danger of explosion Leakage of leachate into groundwater Government control on buildings Credit examples

Total 25 marks

13

5. (a) Using one or more cases studies, describe the effects of volcanic hazards that might result from two of the following:

(i) volcanic ash (ii) volcanic gases (iii) volcanic mudflows (lahars). [15]

MAX 10 if no case study

(i) Volcanic ash- Weight of ash . Ash from fine powder - bombs

Rapid - can be up to 1 metre /hour .Often mixed with water from torrential rain. Causes roofs/walls to collapse Breathing problems, effect on aircraft engines. Examples - Pinatubo, Vesuvius, Krakatoa

(ii) Volcanic gases - Flow of volcanic gas causes suffocation .Rapid, Quiet Little or no warning. Gases include Carbon dioxide, Carbon monoxide and chlorine, fluorine. Sulphur aerosols in the atmosphere. Gas disperses to leave no trace/no damage to buildings. Example - Lake Nyos, Cameroon

e.g. Overturn of volcanic lake, density of gases in hollows

(iii) Mudflow/Lahar - Rapid burial by forceful flow of mud/ash plus rock

Speed - Rapid qualified (45km/hr). Hot (100oC). Caused by lake overflowing/torrential rain/melting ice cap. Little warning given to evacuate. Difficult to predict. Sets like cement. Examples - Nevado del Ruiz/Mount Ruapehu (NZ)/Pinatubo Credit examples

(max 7 plus 1 each)

14

(b) Explain how the movement of underground magma may result in indicators that can be used in the prediction of volcanic eruptions. [10]

A range (at least 2) from monitoring changes in:

Ground deformation

As stress increases with filling of magma chamber, strain causes deformation of volcanic cone leading to increasing slope angles and increased distances across the vent/height of vent. Changes in slope angle measured by Tiltmeters. Description of their mechanism. Changes in distance - EDM (electronic distance measurements) from known fixed points. Laser reflections etc.

Gravity and thermal anomalies

Gravity - Explanation of the method High and low changes indicate changes of mass beneath volcano which equates to rising magma. Thermal anomalies - measured by satellite imagery. Hot rocks identified from space. Thermal anomalies - measured in lake temperature changes. Problems with this method (Water heats slowly/influx of colder groundwater/rain masks effect of temp rise etc)

Gas emissions

Changes in gas emissions - SO2 etc. Degassing of vent during pressure release as magma moves to surface. Decrease in gas - vent blocked = explosion. (COSPEC) Example(s) essential credited. Holistic.

Seismic activity

Increase in activity. Large number of foci. Confined pattern/fingerprint. Harmonic tremors of long duration and low amplitude. Holistic (max 5 each marks)

Total 25 marks

15

GL4 K/U A

1. (a) (i) From ~1310 {range 1320-1300} to ~1175 {range 1185- 1165} accept either way around [1]

1

(ii) High temp = Mg rich and Low temp = Fe rich [1] (no credit for 3.2 and 4.3)

1

(iii) Olivine is first to crystallise/at highest temp (1) High density mineral (1) thus Gravity settling (1) Cooling too quick to allow olivine to react back (1) (Max 3 marks) [3]

2 1

(b) (i) Pyroxene/ Augite (1R) Explanation Next mineral to crystallise/next in sequence (1)

corona structure (1) Overgrowth around olivine/before amphibole (1)

(2 max) [3]

3

(ii) 4. Plagioclase 3. Amphibole 2. Pyroxene (min X) 1. Olivine

(2marks for 3 in sequence, 1 mark for one pair in correct order) Explanation HOLISTIC Olivine first to crystallise/at high temp (1) Is surrounded by lower temp minerals (1) As reaction is not complete (1) Na rich plag – stable at lower temperatures (1)

(2marks max) [4]

4

(c) Grain size large/euhedral/well formed (1) thus slow cooling/long time to form (1) Not slowly enough to allow olivine to completely react back/not reaching equilibrium.(1R) [3]

3

Total 15 marks 3 12

16

K/U A

2. (a) (i) Granite (1) [1] 1

(ii) Least – Hornblende (1) Most – Quartz or muscovite (1) [2]

2

(iii) Hydrolysis (1) Hydrogen ions and water are reactive (1) Clay minerals (Kaolinite) (1) plus (K and Si) ions in solution (1) (max 3 marks) [3]

2 1

(iv) PROCESS: Oxidation (1) iron rich minerals (biotite and hornblende)(1) PRODUCT: to leave iron oxides/rust (1) Process 1max, Product 1max [2]

1 1

(b) (i) Suspension / Suspended [1]

1

(ii) Negative correlation/High in river water/low in saline water (1) Exponential/non-conservative/Immediate drop on mixing

with saline water/changes v quickly/Rate (1) [2]

2

(iii) Clay particles deposited (1) Flocculation (1) Clay particles group/stick together to become heavier (1) Saline water reduces repulsion between grains/elect

charges (1) NOT CREDIT: salt particles binding to clay to make it

heavy (Max 3 marks) [3]

2 1

Total 14 marks 7 7

17

K/U A

3. (a) (i) Silurian (1) [1] 1

(ii) Carboniferous (1) [1]

1

(b) DESCRIBE (1R plus 2max) increase with time (1R) decrease (not just regurgitation of ‘anomaly’) at end of Perm/Trias(1) use of numbers (1) increase in rate (1)

2 2

ACCOUNT (any 3 max) Mass extinction (or equivalent deaths>births for some time) (1) Possible relevant cause (1) eg. Climate change, ice age, meteor, volcanic activity, sunlight blocked development (1) (Min 1R plus 3) (max 4 marks) [4]

(c) 1. Tail (1) swimming (1) 2. Feet/legs (1) Walking (1) Credit sensible others (e.g. Rib cage – protect lungs, Streamlined – Swimming, Nostrils – land respiration) [4]

4

(d) Holistic – mention of Predation/Scavengers Weathering/Erosion before/after burial Diagenesis Bias against terrestrial organisms Bias towards those with hard parts Decay after burial Metamorphism – tectonic activity. (max 3 marks) [3]

3

(e) HOLISTIC Plants - source of food for land vertebrates/habitat (1) Oxygen levels (1R) (inc to sustain land life) Need to develop before vertebrates can colonise the land.(1) (2 marks max) [2]

2

Total 15 marks 5 10

18

K/U A

4. (a)

1

Marks for completed map (max 10) [10] 10 1 – B vertical/N-S (1)

2 – B stops at fault (1) 3 – Permian shading, south of C (1) 4 – C NE-SW trend, not hitting the fault (1) 5 – B cross cuts C (1) 6 – D cross cut by C (1) 7 – Ord or Sil shading in correct place (1) 8 – E cross cuts D, but stops at C (1) 9 – E dyke with NW-SE trend (1) 10 – alluvium cuts across E (1) Plus 11 – B = 20m/6mm AND E is thicker (1) 12 – any correct dip arrow (5° or 40°) placement with number (1)

(b) Thrust (1) accept reverse, but not a list Low angle (1) Hanging wall upthrown/foot wall downthrown (1) (3 marks) [3]

2 1

(c) CRITICAL EVALUATION (1) Could be a Strike-slip fault (1) Left handed (sinistral) (1) Fault valley forming along line of weakness (1) But …. Might not be in situ(1) – deposition/erosion by river (1) Hard to tell/no evidence/possible/unlikely (1) Throw on a dipping fault (1) Dyke swarm (1) (Max 3 marks) [3]

3

Total 16 marks 2 14

19

K/U A

5. (a) (i) Head (1) [1] 1

(ii)

Outcrop pattern

Measurement/description

Maximum NW – SE length

• 2.125 km (2 km – 2.25 km)

Maximum NE – SW width

• 1.125 km (1 km - 1.25 km)

General shape

Elliptical/circular (or equivalent)

1

Max 3 marks [3]

3

(b) Dome/pericline/anticline/antiform (1R) symmetry (1) explained/use of numbers/width of outcrop (1) plunging in all directions (1) open fold (1) NW – SE trend (1) Other relevant (eg. oldest rock in centre) (1) (max 4 marks) [4]

3 1

(c) (i) X [1] 1

(ii) Tick on downthrow side.(1) [1] 1

(iii) Outcrop in valley (1) V’s NE (1)

In direction of dip (1) [2]

1 1

Total 12 marks 4 8

20

K/U A

6. (a) Pb/Pb ore/ Lead/galena (1) [1] 1

(b) (i) NE – SW – 25 (1) SE – NW – 17 (1) Accept tally, even if not written in the totals [2]

2

(ii)

Accuracy (ref to answer in (i) (1) + (1) Both directions (1) Max 3 marks [3]

3

(iii) DIRECTION: Max NE – SW (1) Reference to other directions (1) DISTRIBUTION: Linked to limestone/or areas (1) ACCOUNT Jointing/faults/folding/stress direction (1)

(max 3 marks) [3]

1 2

(c) (i) Con: No downthrow tick shown, No displacement. Gently curved thus steep not vertical

Pro: Same trend as some of other faults, Linear (2 max marks: 2 valid points [2]

1 1

(ii) Slickensides (1) (Accept breccia, gouge, drag folds, alignment of clasts

Explained – movement etc (1) [2]

2

Total 13 marks 4 9

21

K/U A

7. (a) (i) 2 main points – a high over Cw and a low over CwSh (1) 150 (1)

1

[2] 2

(ii) HOLISTIC 1. Shale Low (though high amounts) Shale is impermeable Radon soluble in water Water is unable to act as a transporting agent Drift deposits above may prevent gas escaping (4 max, 4 valid points) 2. Carboniferous Limestone High (though in smaller amounts) Limestone permeable Radon soluble in water Allows the rapid passage of radon in solution No drift covering (4 max, 4 valid points) [4]

2 2

(b) Holistic approach 1R for Geological suitability of site 1R for Potential pollution 1R for Investigation

Discussion of length/width/depth Permability of tuff needs assessing Anticlinal structure - leakage down dip Stability on steeper slopes Limestone permeable – leakage at depth Problem of radon (levels in the valley) Problem of Pb contamination Acid mine drainage Other possible (eg. faults – leakage, reactivation)

(Max 5 marks) [5]

3 2

Total 12 marks 5 7

22

GL5 UNIT 1 Quaternary Geology

Section A 1. (a) (i) 10 cm/s (1) 1 cm/s (1) (ii) Greater velocity is required to overcome inertia of the grain (1) once

moving it has momentum so less velocity required to keep it moving (1) more energy needed to pick up than deposit (1)

(b) Higher velocity to produce the energy required to separate the clay particles

(1) which have flocculated (1) because of a small charge (1) cohesion (1) stick together (1)

(c) (i) 90 to 110 cm/s (1)

(ii) Grains are well-sorted (1) because stream velocity would have been fairly constant (1) transporting finer material downstream (1)

Slight grading (1) so slowing current (1) (Require description and explanation) (d) Sediment is likely to be fluvioglacial (1) because the grains are rounded (1)

because of attrition (1) sorted (1) imbricated (1) indicating a unidirectional flow (1)

2. (a) (i) Clay has more water at the surface / Chalk has less (1) Clay has greater density of channels / Chalk has less (1) Clay has dendritic drainage pattern / Chalk trellised (1) Any 2 (ii) Clay is impermeable increasing drainage density (1) Chalk is

permeable, reducing drainage density (1) . Clay has uniform resistance to erosion (1) The water is exploiting weaknesses (joints etc) in the Chalk (1)

(b) Cuesta (1) dipping beds (1) dip slopes with longer streams (1) escarpments

with shorter streams (1) related to trellised drainage pattern (1) (c) Formed by water erosion (1) no longer active (1) permafrost (1) during

periglacial conditions made Chalk impermeable (1) OR Erosion occurred when water table was higher (1) water therefore flowed at the surface (1) caused erosion (1) water now underground (1).

Either argument acceptable. Holistic mark.

23

Section B 3. “There is a link between continental ice sheets and sea level”

Evaluate this statement with reference to the geological evidence for sea level change. [25]

Description of isostatic sea level change in response to mass of ice locally on the continents. Eustatic sea level changes in response to changing volumes of continental ice and seawater during glacial/interglacial cycles. Superimposition of the two cycles of sea level change (and their differing rates) to create the landforms and evidence seen today. Raised beaches Drowned valleys (Rias/Fjords) Submerged forests/terrestrial deposits offshore Marine deposits on land Coastal features now inland

Credit for examples Evaluation : Is geological evidence for isostatic or eustatic ? Both ? 4. (a) Explain the link between sedimentary processes and products in modern

turbidity current environments. (b) Evaluate the use of sole structures in determining current directions in ancient

turbidite deposits. [25] (N.B: below is re specification. Could interpret as fluvial turbidity currents.) (a) Description : Processes : slope failure and downslope transport Products : turbidites / greywackes / black shales associated sedimentary structures Higher levels to clearly establish links between processes and products e.g. sudden loss in current velocity resulting in grading. Modern should also be addressed - continental slope / submarine canyons (at

higher levels). (b) Evaluation : Identification of sole structure e.g. Flutecasts: formation ? Excellent indicators of current direction. Load casts: formation ? Not related to current direction. Any other relevant structure credited.

24

5. (a) Explain how fossils can be used to provide evidence for Quaternary climatic fluctuations in Britain.

(b) Evaluate the use of Radiocarbon (14C) dating in determining the duration and

rate of these fluctuations. [25]

Description :

Pollen Well preserved, easily fossilised abundant material Sampled from sediments of different types, particularly lake deposits Relative abundance of pollen types used to reconstruct vegetation community Fluctuating climate causes change in the vegetation community Pollen therefore acts as proxy data for climate Glacial/pretemperate climate dominated by Juniper & Birch As climate warms vegetation dominated by deciduous trees (Oak, Elm, Alder) As climate cools, conifers (Pine & Fir) begin to dominate followed by Birch Use of Pollen diagrams to present data Vertebrates Examples of Quaternary vertebrates – Wooly Mammoths, Hippopotamus, Hyena, Bison etc. Application of uniformitarianism – relating modern mammals to fossils Mammoths found preserved in glacial ice. Heavy fur coats as an indicator of colder conditions. Use of individual species, rather than community, to reconstruct climate – mutual climatic range Problems of fossilisation for large vertebrates Other Credit for other organisms used e.g. Beetles, Forams (for Oxygen isotopes)

Evaluation : (b) Timescale provided by dating ONLY organic material by 14C dating

Small quantities of radioactive 14C incorporated into living organisms from atmosphere Decays over time / short half-life / of 5730 years Problems of short period of time that can be accurately dated (40-60,000 years BP) Problems of contamination & variation in production rates of 14C Zone fossils within Quaternary Used for relative dating and correlation.

25

GL5 UNIT 2 Natural resources

Section A 1. (a) (i) NE-SW (1) and NW-SE (1) (or similar ENE-WSW etc) (ii) around the edges of the granite (1) roof zones/tops of granites (1) (Holistic approach to detailed distribution e.g. western Lands End granite) (iii) joints (1) faults (1) fractures (1)

(b) (i) granite (1) country rock / sediments(1) (ii) groundwater (1) magmatic water (1) (iii) heat from granite (1) draws in cool groundwater, heats it and cause it

to rise (1) and cool (1) and then is drawn back in again.

(c) Concentric layers/zones least soluble minerals closest(tin/copper) (1) most soluble further away(lead/zinc) (1) As hydrothermal fluids travel away from granite they cool and deposit minerals according to temp of crystallization (1). Holistic.

2. (a) (i) unconformity (1) fault (1) (ii) along bedding planes up dip (1) along fault planes (1) (iii) porosity – sandstones up to 30% controls volume held (1) permeability – controls rates of flow/extraction (1) effect of grain size (1) shape (1) sorting (1) cement (1)

(b) (i) 2.5km (2.3 to 2.7km incl) (1) 110℃ (105 to 115℃ incl) (1) (ii) At higher temperatures hydrocarbon chains break into shorter lengths

(1) oil breaks down to gas below 4km (1) Below 5km hydrogen is lost leaving only carbon (graphite) (1)

Section B

3. (a) Describe the method of extraction of one type of geological raw material. (b) Evaluate the potential environmental problems and how they may be

minimised. [25]

Description : Explanation depends upon case study of raw material. Expect - coal extraction by deep mining/open cast salt extraction by brine pumping/underground mining offshore/onshore oilfield development quarrying for roadstone / aggregate sand and gravel extraction Evaluation : N.B. Higher grades so need to evaluate the problems. Potential environmental problems e.g. Noise, dust, pollution of water courses by chemical/waste, waste disposal etc And the ways by which these may be minimised e.g. restricted blasting, baffle banks, settling tanks, backfill etc. How significant are the problems and the way(s) that they are minimised? Case studies to show planning to satisfy local or national legislation for max levels of pollution.

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4. Evaluate the use of two of the following exploration techniques. [25]

Drilling and downhole logging Description : Drilling to assess 3 dimensional shape and size of ore-body Assessment of grade and tonnage of ore body – rock geochemistry Chemical analysis – atomic absorption spectrometry (AA) – X-Ray fluorescence spectrometry (XRF) – inductively coupled plasma mass spectography (ICPMS) Assessment of results – decision to mine or not

Downhole logging is the process of measuring physical, chemical, and structural properties of penetrated geological formations using logging tools that are either lowered into the borehole on a wireline cable (wireline logging) or placed just behind the drill bit as part of the drill pipe itself (logging-while-drilling). The tools employ various acoustic, nuclear, and electrical measurement techniques to acquire downhole logs of properties such as sonic velocity, density, and electrical resistivity. The wireline cable provides real-time communication between the tools and the surface. Evaluation : Advantages : reliability of data Disadvantages : cost / invasive etc

Geophysical surveying Description : Techniques e.g. seismic magnetic gravity Evaluation Advantages : speed / accuracy / cheap? Disadvantages : depends on target / cost? Description - seismic /explosions / land / ship / reflection / record of 2-way time / graphical representation to identify structures / oil traps - magnetometer / land / plane / ship / graphical representation of magnetic readings / depends on changes in magnetic properties or distribution of rocks i.e. structures / anomalies - gravimeter / changes in gravity / changes in density of the underlying rocks / reflects the rocks / minerals / structure(s) / graphical representation / anomalies

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Geochemical prospecting Description : Sampling stream, soil or vegetation to find particular trace element concentrations which might indicate the presence of an economic resource. Concentrations vary with distance from the ore body. Copper and lead. Evaluation Advantages : sampling allows large catchment area to be investigated quickly all elements have a characteristic signatures which may show up in vegetation response and are easily recognised in soil and water samples very dependable and cost effective Disadvantages : Contamination can be a problem (earlier mining, processing, wind blown, flooding) Background rocks, variations in water pH, and ore concentrations can give misleading results. Access may be difficult over wider areas. Geological mapping Description : Field work based – direct observation using trained geologists. Evaluation Advantages High level of accuracy to pinpoint resources at the surface prior to exploitation. Can be very detailed – good to assess the problems of exploitation and viability of resource. Samples can be collected for accurate analysis. Disadvantages Labour intensive an time consuming. Accuracy depends upon sample points and interpretation. Possible problems of access in remote areas and lack of outcrops. Satellite remote sensing Description : Radiation is absorbed and reflected in different ways by different materials Materials emit different types of radiation depending upon temperature and molecular structure Emitted and reflected radiation can be monitored analysed and displayed as a visual image Suitable for major metalliferous deposits (e.g. copper, iron) Evaluation : Advantages Provides a large scale image relatively cheaply. Inaccessible areas studied easily. Large scale structures show up which might be missed in the field. Satellites are generally in place – only need to buy image required. Disadvantages Used for only basic reconnaissance. Interpretation. Colours can be misleading.

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5. (a) Evaluate the suitability of the physical properties of one mineral or rock for industrial use.

(b) Use a flow diagram to describe the processing of one element or compound

from its raw material. [25] (a) Description : Valid choice of mineral or rock and industrial application. List of properties plus discussion of significance of properties. Evaluation : Fit for purpose? Best? or better alternatives? (b) Diagram from extraction of raw material to production of element or

compound.

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GL5 UNIT 3 Geological Evolution of Britain

Section A 1. (a) (i) Near to mountains (1) fault scarp (1) position of streams (1) flat plain (1) (ii) HOLISTIC Conglomerates high energy / flash floods high degree of erosion Poorly sorted indicates dumped on losing energy Cross bedded sandstones deposited as current lessens and spreads out Few mudstones indicating high energy Cyclic / rhythmic sedimentation / wet / dry seasons / flash floods evidence (1) Explanation (2) (iii) Cross-bedding / asymmetrical ripples to show current direction diagram (1) current direction (1) (b) (i) Fining upwards cycles (1) (ii) Coarse to fine grained decreasing energy (1) cross to planar

stratification (1) decreasing energy (1) (iii) Fluvial/river (1) 2. (a) (i) Low viscosity magma (1) (ii) Plutonic centres N-S trend (1) along W coast of Scotland (1) dyke swarms from volcanic centres (1) / NI and Wales (1) across NE England (1) NW-SE trend (1) (b) (i) 60.53 – 58.9 = 1.6Ma (1) (ii) Granite younger granite intrudes gabbro western edge of granite similar to gabbro / experimental error eastern radiometric date younger than gabbro Holistic. (iii) Heat from gabbroic magma melts continental crust (1) OR fractional �rystallization of gabbroic magma (1) (c) Basalt from partial melting of mantle mantle plume / hot spot beneath northwest Britain tension in continental lithosphere opening of North Atlantic basalt magma rises to surface becomes ocean spreading centre continents move away from plume so volcanic activity ceases Holistic.

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Section B

3. “During the early Palaeozoic the northern and southern parts of Britain were on different continents separated by the Iapetus Ocean.” Describe and evaluate the geological evidence which supports this statement. [25]

Description : Sedimentary Rocks

Shelf sediments in NW - Torridonian Sandstone (Precambrian) - limestones and quartzites (Cambrian)

Deep marine sediments to SE Graptolitic shales and turbidites (Ordovician) Shelf sediments to SE - quartzites, conglomerates and limestones Deep marine to NW graptolitic shales (pelagic sediments) and turbidites. Fossils Distinct benthonic trilobite / brachiopod faunas in SE and NW during Cambrian merge in Ordovician Palaeogeography Stable shield areas separated by a wide ocean Evidence of later continent / continent collision - Caledonian orogenic Belt. Closure of the Iapetus ocean. Evaluation :

NW and SE passive plate margins / trailing edges separated by constructive plate margin ?

Evidence of ocean crust - ophiolites in various parts of Britain No evidence for width of ocean Graptolites extinct - mode of life debatable. Plankton found in sediments of all depths. Trilobites and brachiopods - faunal provinces ?

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4. “The effects of three major orogenies can be demonstrated in Britain.” Describe and evaluate the evidence which supports this argument. [25] Description : Caledonian Moine Thrust along NW margin of orogenic belt. Early phases show large scale folding and nappes in Scotland Formation of major faults such as HBF and GGF Later phases show lower degree of deformation. NE-SW structures in Scotland, Lake

District and Wales. Deformation complete by end of of Lower Palaeozoic. High grade regional metamorphism in Scotland. Lower elsewhere. Granite intrusions in Scotland and L.District. Less so in Wales. Evaluation :

Convincing evidence for Caledonian orogeny with association of deformation, metamorphism

and intrusion across Britain. Continuous with Scandinavia and N.America. Description : Variscan Underthrusting along the Lizard Thrust Zone and obducted ophiolites. Affects mainly Devonian and Carboniferous rocks. Tight vertical / overturned folding with E-W trend in SW Britain. Folding less intense to north. All trends. Pennines N-S. Some reactivation of Caledonian structures. Coalfields preserved as synclinal basins. Low-grade metamorphism to SW. Cornubian granites plus mineralisation. Volcanicity in north - Whin Sill. Evaluation : Convincing evidence in SW - less evidence further north. Description : Alpine Gentle folding on margin of orogrnic belt. Wealden Dome separating London and Hampshire Basins.

IOW-Purbeck-Weymouth line. Monoclinal folding with vertical northern limb. E-W trend.

Tertiary age. No metamorphism / igneous activity. Evaluation : Little evidence of orogeny in Britain - need to look elsewhere.

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5. Palaeomagnetic evidence suggests Britain drifted north across the equator in the

Late Palaeozoic. [25] (a) Describe the effects on the sediments and fossils. (b) Evaluate the reliability of the palaeomagnetic evidence. (a) Description : Carboniferous equatorial carbonate platform Bioclastic and oolitic limestones re Law of Uniformitarianism. Colonial corals / reefs Brachiopods Coal / seatearth / abundant vegetation / tropical forest / swamp Cross-bedded deltaic sandstones Abundant plant fossils - ferns, tree ferns Insects / amphibians Permian desert

Red sandstones / haematite / iron oxide staining / well sorted, rounded / aeolian dune bedding / evaporites / breccias / desiccation cracks

Rare fossils / tracks / trails / footprints (b) Evaluation :

Reliable data will give low angle magnetic inclination, decreasing to zero and then to a low angle again

Assumes dipolar field Assumes rocks undisturbed / tectonic / metamorphism Inaccuracies in dating methods

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GL5 UNIT 4

Geology of the Lithosphere Section A

1. (a) Max / int / min (1 for 1; 2 for 3) (b) Correct equation (1) 30 to 36 (1) (c) (i) 640 to 700(incl) deg (1) 50 to 60(incl) km (1) (ii) Was sea-floor absorbed sea water (1) (d) Origin: metamorphosed sediments (1 Reserve) / overall granitic /

lighter (1) (e) Subducted basalt / partial melting / + granitic crust contamination (stoping) Holistic. 2. (a) (i) Normal / rift / tensional (1) (accept : transform) (ii) Tension / extension (1) (shear for transform) (b) Deeper faulting - more brittle deeper below SL - buoyancy / isostasy / rising plumes curved - change of stress direction / material with depth ? more faults in b - slower plate movement feature (1) explanation (1) (c) (i) Y : 4.2 + 4.3 = 8.5 (2) Z : 4.3 - 4.2 = 0.1 (2) (ii) Y sinistral / Z sinistral (2) (iii) Greater relative movement (1) sea floor moving in opposite directions (1) more friction (1)

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Section B 3. Describe how heat is lost through the Earth's lithosphere and evaluate the relative

importance of the ways that you describe. [25]

(Question could be tackled in one of two ways. Ideal below but more likely an account of convection in the mantle and associated plate tectonics / hot spots / convection / sea-floor spreading / volcanism black smokers / geysers.)

Description : Heat transfer : conduction / convection / radiation. Conduction : rocks poor conductors. Internal heat conducts through solid Earth (mantle and lithosphere) to the surface. Oceanic lithosphere cools by conduction as it moves away from a spreading centre, leading to a thickening of oceanic lithosphere with age. (i) Interpretation of heat flow variation across an ocean basin.

Convection : Re plate tectonics. Occurs in solid mantle as well as liquid outer core. Plate margins / volcanicity. CPM v DPM. (Conservative ?) Diapirism / continental igneous activity. Hydrothermal at oceanic ridges. Convection of heat from surface via atmosphere. Radiation : Infra-red. Volcanism.

Evaluation : (Difficult to assess relative importance.) Convection very high over small area. Conduction low over very large area. Radiation very low everywhere. Generally accepted that passage of heat through the outer layers of the lithosphere is predominantly due to conduction.

4. Describe how forces acting on continental lithosphere may cause brittle or ductile

deformation. Evaluate the importance of the depth in the lithosphere on the types of deformation produced. [25]

Description : Forces (principal stresses) produce folding (ductile) and/or faulting (brittle). Depth v breadth : Relationship between stress orientation and type of deformation. Stress / strain curves. Elastic v plastic. Elastic limit. Faulting before elastic limit. Folding beyond elastic limit. Effect of temperature. Evaluation :

Depth = increase in temperature (geothermal gradient) and pressure. DPM v stable lithosphere (cratons etc). Relate to stress curves / how depth may effect shape / position of curves / resulting strain.

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5. Describe how a rate of seafloor spreading may be calculated. Evaluate the accuracy of any methods(s) you describe. [25]

Description : Rate = distance / time. Distance measured (probably) from map / survey of magnetic stripes. GPS Time = age of sea-floor rock / basalt. Age is radiometric age (details). This would give an “absolute” rate. Graph for average rate. Variable rate? Hot spots / Hawaii (Emperor Chain) Magnetostratigraphy. Use of sediment thickness and fossil content ? Evaluation : Accuracy : Collection of specimens? Distance = very accurate = theoretically to mm (GPS). But - where is the ridge axis? (equal rate in both directions?) Age +/- 10% ? (depends on method) 1. GCE Geology-MS (Summer 2008) JF

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