MS3 WELSH JOINT EDUCATION COMMITTEE

£3.00 CYD-BWYLLGOR ADDYSG CYMRU

General Certificate of Education Tystysgrif Addysg Gyffredinol

Advanced Subsidiary/Advanced Uwch Gyfrannol/Uwch

MARKING SCHEMES

SUMMER 2004

GEOLOGY

INTRODUCTION

The marking schemes which follow were those used by the WJEC for the 2004 examination

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.

The WJEC regrets that it cannot enter into any discussion or correspondence about these

marking schemes.

1

GL1

K/U A

Q.1 (a) Point A = arrow pointing to East/right

Point B = arrow pointing to West/left

Point C = arrow pointing to East/right

3 correct = 2 marks, 1 or 2 correct = 1 mark [2]

(b) (i) D within subducting lithospheric plate or at depth

within the continent. [1]

(ii) S in the lithosphere between the margins of the

rift valley. [1]

(iii) Compression of plates

Subduction of plate

Friction

Pressure build up/stress release [3]

(c) Youngest 1 4 3 2 Oldest = 2 marks [2]

or if not the above, can gain up to one mark max for:

2 as oldest or

1 as youngest or

3 older than 4

(d) Pillow lavas: Eruption into water

Rapid cooling

Formation of "skin" or glassy outer later.

Pillow shape as skin inflates with lava

Basaltic magma: Partial melting

Derived from mantle

Heated by rising mantle convection

Lower pressure/mantle decompression [4]

(Up to 3 max on either section in (d))

3

4

2

1

1

2

For 4 marks, must have both 'eruption into water' and 'partial melting'

reference.

7 6

Total 13

2

K/U A

Q.2 (a) Time taken for half of the parent atoms to decay to daughter

[1]

(b) (i) 5730 years (5100 - 6300) [1]

(ii) 12.5% [1]

(c) Proportion the same between atmosphere and living orgs

because exchange between org and environment.

Less in fossil than atmosphere due to decay of 14

C from

fossils/lack of replenishment from atmosphere. [3]

(Up to 2 marks max for comments related to either living

organisms or fossils)

(d) (i) Carboniferous too long ago

So many half lives have passed

that 14

C too small to measure [2]

(ii) No organic matter in a dyke

14

C only in organic matter [2]

(iii) Organic matter present

within the correct age range [2]

(e) Stating type of example e.g. dyke, unconformity, clast

Precise location for the example

Scale (in text or on diagram)

Quality of drawing/description

Evidence of appropriate conclusion or explanation of law of

included fragments/cross cutting

1

3

2

2

2

5

1

1

15 2

Total 17

3

K/U A

Q.3 (a) (i) Pyrite [1]

(ii) Replacement

Molecule by molecule of original calcium carbonate

shell. [2]

(b) (i) Cephalopod/Ammonoid/Goniatite [1]

(ii) Suture Line

Rounded saddle

Angular lobe

Simple/goniatitic or goniatite type

Become more complex over time [2]

(iii) Loose boulder may not have come from cliff face

Fossil P may be a derived fossil [2]

(c) (i) Shale [1]

(ii) Coal

Shale or Rock A

Sandstone [2]

3 correct = 2 marks, 2 correct = 1 mark

(iii) Grading within the sandstone bed is fining upwards.

Load cast/load and flame structure/convolute

structure correctly orientated as heavier sand

deposited on wet, finer sediment

Plant root fossil in situ, roots pointing downwards

[3]

1

2

1

2

1

2

2

3

9 5

Total 14

4

K/U A

Q.4 (a) Rounded/oval shape

2.5 – 3.5 km diameter [2]

(b) (i) Porphyritic

Phenocrysts or groundmass

Coarse

Crystalline or crystals

Phenocrysts/larger crystals up to 2cm

Groundmass/smaller crystals typically 0.5 cm

Random arrangement of crystals/interlocking/mosaic. [3]

Shape of crystals, e.g. euhedral phenocrysts, sub or

anhedral groundmass. [3]

(ii) Crystals in B all cooled at same rate /constant rate

C had 2 stage cooling

Magma cooled slowly during phenocryst formation

Magma moved higher in crust

Magma cooled quicker when groundmass formed. [3]

(iii) Rock B = Gabbro

Rock C = Granite [2]

(c) (i) Model 1 = Pluton

Model 2 = Sill or lava flow [2]

(ii) Model 1 because

Definition of discordant

Identifying that 2 is concordant or 1 is discordant

Rock B is coarse grained

Coarse grain size suggests formation within a pluton

rather than in a more rapidly cooling sill or lava

flow.

Edge of aureole outcrops on map, Fig 4a, and on

Model 1 only

Credit also given to other well reasoned points. [4]

1

1

3

3

1

1

1

1

4

12 6

Total 16

5

GL2a

Q Response Mark

1 (a) (i) Red-brown 1

(ii) Haematite 1

(b) Clasts

Averaging 1mm diameter

Well-sorted

Rounded (quartz)

More angular (feldspar)

1

1

1

1

1

5

(c) (i) 1 Use steel pin to scratch/break rock

2 Crumbles easily

1

1

1 Add few drops of water

2 Soaks in quickly

1

1

4

(ii) the porous nature or the ease of disintegration

suggests a low degree of cementation

1

1

2

(13)

2 (a) (i) L = pedical opening

M = hinge line

1

1

2

(ii) 1 Vertical line drawn through umbo at 90º to hinge

2 Fossil is not equivalve, but inequivalve

Fossil has a larger (pedical) valve and a smaller

(brachial) valve

2 max

1

2

(b) (i) Positive acid test

Rhombic cleavage

Calcite

1

1

1

3

(ii) Brachiopod = benthonic (shallow) and marine

(uniformitarianism)

Calcite = forms easily by organic/chemical ppt in warm

seas

X-beds show reversal = tidal current wave ripples =

shallow

1

1

1

3

(11)

6

Q Response Mark

3 (a) (i) "discordant" 1

(ii) Draw to scale

Non-parallel sides

Cooling joints or clasts in country rock

Chilled margin labelled

Baked margin labelled

1

1

1

1

1

5

(b) (i) Medium crystal size (2mm)

Mafic composition

1

1

2

(ii) Coarser crystals

Larger body takes longer to cool

1

1

2

(c)

1

1

1

1

1

1

6

(16)

4 (a) (i) Correct label 1

(ii) Weathered surface beneath

Basal Conglomerate in hollows

Included fragments above

Borings into lower rock group

Any 3

3

(iii) N-S axial plane traces correctly positioned and labelled Any 2 2

(b) (i) True = fault cross-cuts on Map 1

False = sinous outcrop on Map 1 suggests low angle of dip

False = older rocks must be on the upthrown side

1

1

1

3

(ii) Thrust 1

(10)

H

C

D

E

Faulting

Folding

7

Q Response Mark

5 Extend F2 to west (across small Valley on profile)

Correct movement on F2

Base of A (unconformity)

Correct cross-cut between unconformity and F2

H beneath unconformity

R S T plotted above F2 in thrust slice

Antiform correctly positioned and labelled in thrust slice

Synform correctly positioned and labelled in thrust slice

1

1

1

1

1

1

2 max

2 max

10

(10)

8

GL3

Questions Marks

1. (a) (i) A – decreases

B – increases (1) [1]

(ii) 1959 – 0 cm

1969 – + 20 cm (1)

20 cm/10 years = + 2cm/yr (1) [2]

(iii) C – little/no significant change in length (1)

C – both ends of survey line on same fault block (1)

B – crosses the fault/extension (1) [3]

3

(b) Arrows showing dextral strike slip (1)

D – shows extension over time (1) [2]

2

(c) Reduction in extension or compression along a survey line (1)

shows build up of stress (1)

Seismic gap (1)

Some move faster than others (1)

Thus increase chance of an earthquake (1)

(Max 2 marks) [2]

1

1

(d) One explained from:

groundwater levels/pressure

tilting/ground elevation

radon gas emissions

electromagnetic signals

electrical resistivity

animal behaviour

earthquake lights

changes in seismic activity

Other appropriate explained

(Max 3 marks) [3]

3

Total 13 Marks

4

9

9

Questions Marks

2. (a) Solid rock surface beneath drift (1)

(b) (i) Explosion/pressure-air gun/etc. (1)

(ii) 100m – Direct

200m – Refracted

(iii) Direct waves arrive first over short distances/

Refracted waves arrive first over longer distances (1)

Refracted waves travel further to reach geophone. (1)

As they have a greater velocity in solid rock than drift (1)

Solid rock more incompressible/rigid (1)

(Visa versa for direct)

(Max 3) [3]

1

2

(c) In Figure 2a – Rockhead linked on boreholes (1)

Showing valley at 60m (1) [2]

2

(d) Two of the following explained:

1. Porosity/permeability

Effect of water table/pressure explained

2. Structural weaknesses

(bedding/faults/cleavage/joints) explained

3. Rock competency

plastic deformation, etc.

4. Depth to rockhead

thickness of weak, unconsolidated drift in buried valley

Other suitable, must be GEOLOGICAL property

(Max 2 per property explained) [4]

2

2

Total 12 Marks

5

7

10

Questions Marks

3. (a) Describe how sites of potential slope failure can be monitored.

Mechanics of mapping, air photo-satellite imagery, surveying,

measurement strain, groundwater pressures described.

Instruments used.

Accept volcanic slope monitoring (Mt. St. Helens).

(Max. 10 marks)

(b) Explain the factors that can trigger or contribute to mass

movements or rock and soil.

Angle of slope:

Slopes above 35 degrees are often unstable (exception –

solifluction, etc.).

Friction is greater than forces of gravity.

Result = rockfall/slides, rotational slip, stumping.

Lithology/Load:

Shale, clay, etc. – are incompetent and will flow/slip under load

pressure and lubrication – rotational slip.

Sandstone/Limestone – joint patterns/bedding.

Crystalline igneous and metamorphic = strong but less stable if

cleavage present.

Weathering/Shrinkage and expansion:

Competent rock (granite) is reduced to clay – loses cohesion

between grains/joints density.

Physical/Chemical/Biological effects on rocks.

Groundwater/rainfall:

Acts as a lubricant to accelerate movement by reducing friction

between blocks/particles. Pore pressure, erosion.

Ground vibration:

Loss of friction/cohesion between grains and discontinuities.

Orientation of discontinuities:

Unstable friction angles.

KU A

Breadth v depth.

(Credit for examples and diagrams)

25

-

Total 25 Marks

11

Questions Marks

4. (a) Using one or more case studies, describe how two of the

following volcanic hazards have resumed in toss of life and

damage to property.

(i) Blast/explosion

Explosive index – Types: - Hawaiian – Ultra Plinian.

Lateral blast - e.g. Mt. St. Helens – heat, speed, force,

distance travelled.

Vertical blast – e.g. Pinatubo, Krakatoa.

Secondary effects -trees levelled, rivers blocked by debris, effect of bombs/ash, etc. tsunamis.

(Max. 7 plus 1. No case study – Max. 3 plus 1)

(ii) Mudflow/lahar

Reworked ash from volcano.

Hot, liquid.

Consistency of concrete.

Melted snow and torrential rain.

Lasts for years.

Difficult to predict.

E.g. Armero (Columbia)/Pinatubo, etc.

(Max. 7 plus 1. No case study – Max. 3 plus 1)

(iii) Volcanic gases

Variety – CO2, H2S, CO, SO

2, etc.

- contain fluorine, sulphur, chlorine – noxious.

Hot (1000C).

Effect on vegetation.

Not affecting buildings but kill people.

Lake overturn – Lake Nyos (Cameroon).

(Max. 7 plus 1. No case study – Max. 3 plus 1)

(iv) Lava flows

Hot, fluid (depending on composition and temperature).

Can be fast flowing (50km/hr) or slow, travel far (50km)

or not.

Easy to avoid for people/not for property.

Causes fire and loss of property.

Can kill in rare cases (very fluid lava).

E.g. Nyiragongo Congo, Etna, etc.

(Max. 7 plus 1. No case study – Max. 3 plus 1) [15]

12

Questions Marks

(b) Discuss the effectiveness of the methods used to minimise loss

of life and damage to property in active volcanic regions.

Holistic approach relating to:

Evacuation, hazard mapping, diversion/blocks, dropping –

spraying with water, explosion of flow margin, prediction

methods.

Ultimately little management/control if people choose to live

near volcanoes.

Case studies – Iceland, Etna, etc. credited.

(Max. 10. No evaluation of effectiveness – Max. 7) [10]

KU A

Total 25 Marks

25

-

5. (a) Describe how ground subsidence may be related to the extraction

on:

(i) Rock and minerals

Ground instability associated with

Dip strata, rock cleavage, joint patterns.

Orientation of rock discontinuities

Stable friction angles (35 degrees)

Reduction of rock strength by undermining

Associated with underground mining

Surface expression of collapse

Examples credited, e.g. coal and salt extraction.

(Max. 7 plus 1)

(ii) Water

Reduction of pore pressure

Grains readjust position/packing – less volume

Porosity reduced

Examples associated with human extraction from wells

and natural extraction by vegetation (trees).

(Max. 7 plus 1) [15]

(b) Explain how the extraction of rock, minerals and water may

result in the pollution of surface water and groundwater.

1. Mine drainage pollution explained

Pyrite/iron oxidised in acidic mine water

Waste tipping – pollution effect of percolating water

Potential leakage if hole used for landfill.

2. Overpumping – contamination with saltwater explained

Cones of exhaustion result in pressure difference which

draws in saline water in coastal areas. [10]

KU A

Total 25 Marks

25

-

13

GL4

SECTION A

Question 1

K/U A/E

(a) Granite (Granodiorite)/coarse grained acid/siliceous rocks (1) [1] 1

(b) (i) Describe

A B 3 max

Texturally immature Texturally mature (1)

Matrix supported Clast supported (1)

Larger/coarser Finer (1)

Has no cement Has cement (1)

Poor sorting Well-sorted (1)

Angular/sub-angular Sub-rounded - rounded (1)

Explain : Degree of textural maturity in terms of :

More transport/erosion/weathering in B (1)

For longer in B (1)

For further in B (1)

For larger number of erosion cycles (1)

(Or visa versa for A)

rate of deposition rapid in A (1)

(Max 3 marks) [4] 4

(ii) Feldspar has cleavage/quartz none (1)

Impact splits cleavage giving angular shape (1)

Rather than rounding in quartz. (1)

(Max 2 marks) [2] 2

(iii) Feldspar broken down by weathering (to clay) (1) RES

Mineralogically mature (1)

Clay not deposited in higher energy (1)

Hydrolysis(1) stability fields/ref to Bowen’s reaction

series (1)

Details of process (1)

(Max 3 marks- R +2) [3] 2 1

(c) River emerging onto semi-arid plain - A (1)

Beach - B (1)

[2]

1

1

(d) Silica outgrowths from pressure solution (1)

Surround original quartz grains (1)

THEN other pore spaces infilled by (1)

Calcite cement (from percolating fluid) (1)

Accept Packing/compaction/dewatering/lithification (1)

(Max 3 marks) [3] 1 2

Total 15 marks 5 10

14

Question 2

K/U A/E

(a) Anorthite (Calcium rich) (1) [1] 1

(b) Melt P

35% Na :

65% Ca

Temperature of

melt (oC)

Composition of

melt

(% Na: % Ca)

Composition of

crystals

(% Na: % Ca)

Initial

crystallisation 1500

(+/-2)

35:65 10:90

(+/-2)

Crystallisation

at 1400oC

1400 65:35

(+/-2)

25:75

Final

crystallisation 1350

(+/-2)

35:65

(+/-2)

(c) (i) zone I (more Anorthite/calcic-rich)

zone II (more Albite/sodic-rich) (1)

[1]

1

(ii) Ca higher melt point/Ca-rich first to crystallise (1)

solid solution series (1)

Temp drops too fast for equilibrium to be maintained (1)

Crystals unable to completely react back with melt/equilibrium (1) RES

Before more Na-rich crystals form around older crystals (1)

Process continues until crystallisation complete (1)

(Max 3 marks – R +2) [3] 2 1

(d) Fine grained groundmass (porphyrytic texture) (1)

Crystallisation was too fast - rapid cooling. (1)

Ca removed/not left (1)

Not enough time for reacting back with melt - diffusion of ions (1)

(Max 2) [2] 2

(e) Contamination during magmatic intrusion (1)

Xenoliths (1)

Magmatic stoping (1)

Example - peridotite in basalt, mafic rock in granite.(1)

Gravity differentiation/cumulates/gravity settling/fractional crystallisation/or

gravity layering (1)

Eg. Olivine first to crystallise (high crystallisation temp)(1)

Reference to position in Bowens Reaction Series (1)

Olivine more dense than other feldspar/augite (1)

Olivine sinks in liquid magma (1)

Olivine trapped at chilled margins/unable to differentiate (1)

(Max 2 if no minerals mentioned)

(Max 3 marks) [3] 3

Total 15 marks 5 10

15

Question 3

K/U A/E

(a) (i) [4] 3 1

Fault characteristics Description

Strike direction E - W (1)

Downthrow direction North (1)

Amount of strike-slip

movement

None

Principal stress component (σ)

(parallel to strike direction)

σ intermediate (1)

Type of fault Normal/tensional (1)

(ii) Shale - offset to East only (1)

Dyke - no offset (1)

e.g.

[2]

1

1

(b) (i) Number/Coarse (1), angular fragments (1), poor sorting(1),

parallel alignment of clasts (1)

fault breccia/(cata)clastic texture/fragmental (1).

(Max 3) [3] 3

(ii) Brittle fracture (1) of competent limestone (1)

Shale is incompetent (1) 1 RES for competency

Ductile (plastic deformation) when subjected to stress (1)

(Max 2 marks – R +1) [2] 2

(c) (i) Slickensides (or appropriate) (1) [1] 1

(ii) Direction of grooves shows orientation of movement. (1)

(Credit smooth feel in direction of movement) (1)

Assessment: (1 RES)

Not always clear in which of two possible directions (1)

Reactivation possible (1)

Slickensides only record the LAST direction of fault

movement (1)

(Max 3 marks – R+2) 3

Total 15 marks 5 10

16

Question 4

K/U A/E

(a) Mass extinction: - When deaths > births (1)

for many families/species (1)

over short time/at the same time.(1 RES)

(Max 2 marks – R +1) [2] 2

(b) (i)

Mass extinction age Name of flood basalt trap

K-T extinction

(~65 Ma)

Deccan (1)

P-T extinction

(~250 Ma)

Siberian (1)

[2]

2

(ii) Very good/strong correlation (1)

Most correlate with a flood basalt trap of the same age. (1)

Most lie on line (1)

Except (1R) Bajocian/South African(Karoo) or

Middle Miocene/Columbia

(Max 3 – R +2) [3] 3

(c) (i) Dramatic drop/Falls to 0% at K/T boundary from 40% (1 RES)

Rises and falls to 15% max over next 25 cm (1)

Followed by steady rise back to >40% up to 200cm (1)

(Max 2 marks – R+1) [2] 2

(ii) Both peak dramatically at K/T layer (1)

Iridium rises/falls more gradually than spinel (1)

Spinel single spike only at K/T layer (1).

(Max 2 marks) [2] 2

(d) Holistic approach (to include additional knowledge)

Meteorite elements mark the boundary

Indicate a meteorite impact at 65Ma

Correlation does not mean causation

Deccan flood basalt – also potential culprit

Flood basalts have good correlation with other mass extinctions

Sudden reduction of organic content – could be either/both

Organic reduction indicates a rapid event - (impact)

Rather than more gradual climate change - (volcanism)

Other possibilities sea level fall

methane hydrate

oceanic anoxia

environmental change

combination of factors

Credit other details.

(Max 4 marks -RES mark for critical evaluation + 3) [4]

4

Total 15 marks 2 13

17

SECTION B

Question 5

K/U A/E

(a) (i) Consolidated/non drift/basement rock (1) [1] 1

(b) Appropriate grid square chosen

8052 or 7951 only (1)

Unconformity label (1) shows a square with unconformity (1)

1

2

(max 3 marks) [3]

(c) (i)

Direction

Angle

of dip

(o)

Name of coal seam Age of

coal seam

SW 15

(1R)

Cannel Row (CR) (1R) Youngest

Chalkey (Ch) Oldest

2 (R) marks plus 1 from stat. order [3] 3

(ii) Mining /excavation/made ground/backfilled excavation (1) [1]

(iii) Erosion of valley etc. (1)

In direction of dip , Principal of “v”s (1) [2] 2

Total 10 marks 4 6

18

Question 6

K/U A/E

(a) (i)

Fold characteristics Western Anticline Potteries Syncline

Axial plane trend Both : NNE - SSW

Axial plane dip

angle (degrees)

and direction along

section.

Angle

(degrees)

Direction Angle

(degrees)

Direction

~50

(40-60)

SE

(SSE-

ESE)

~70 NW

Fold symmetry Both : Asymmetric

Orientation

(direction) of the

maximum

principal stress

component (σmax)

Both : ESE - WNW

[3]

1 2

(ii) Oldest rock in centre (1)

Dip away from axial plane/upfold etc (1) [2] 2

(iii) Both plunge to SW (1 + 1) [2] 1 1

(b) (i) 6.2 (+/-0.2)cm x 110 (1) = 682m (660 – 704) (1) [2]

2

(ii) 1. Both normal (1) (hanging wall=downthrow) (1)

(credit - reactivation possible?)

2. Red Rock Fault has larger throw (1)

3. Faults result from tension (1)- folding from compression (1)

(Faults (σmax) vertical, Folds (σmax) horizontal/NW-SE)

(R one from each (1 - 3) plus 1) [4] 4

Total 13 marks 4 9

19

Question 7

K/U A/E

(a) (i) Decrease(1) Increase/level off (1)

Accuracy (1) [3] 3

(ii) Distribution – V-shape (1) grid refs (1) Areas (1)

related to coal measures (1)

Extent – Graph described/use of numbers (1)

(max 2 max)

Underground mine collapse (1)

Abstraction of water (cones of exhaustion etc) (1) [3] 3

(iii) Possible reference to

No of coal seams mined (1)

Depth of seams (1)

Rock strength (1)

Barren v Coal Measures qualified (1)

Fault movement (1)

(Max 2 marks) [2] 2

(b) Subsidence qualified - Mining subsidence – differential (unrecorded mine

workings) Made ground

Stability of faces/landslides on backfilled faces

Gas explosions – methane leakage

Flooding and surface groundwater pollution

Faulting – reactivation

Earthquakes – mining collapse

Mining collapse

(HOLISTIC Max 4 marks) [5] 5

Total 13 marks 5 8

20

GL5

UNIT 1 - QUATERNARY 1. (a) Earthquake (1)

Storm (1) Slump (1) Instability etc specified (1) [1] (b) (i) Velocity = Distance/Time or (260+10) / 2 (1) = 130 (125 - 135) (1) [2] (ii) Velocity decreases down slope (1) Angle of slope decreases / energy lost (1) [2] (c) (i) Graded (1) / Cyclic/repeated sedimentation (1) / Clastic (1)

+ (2) for explanation related to processes [4] (ii) Thicker beds in 1c (1) / Erosive surfaces in 1c (1) Coarse sand in 1c (1) / only 1d has mud (1) +(2) for explanation related to processes [4] 13 marks 2. (a) (i) 2 areas shaded (1) All three areas shaded (2) (4 areas shaded including 3 correct = 1 mark) [2]

(ii) Far north of Britain (1) Colder (1) High Land (1)

Less melting in the summer (1) More precipitation (1) 2 of [2]

(b) (i) Beach sediments above current high water mark (1) Raised beach (1)

Beach sediments on top of till (postglacial) (1) Flat marine erosion platforms (1) Wave-cut platforms (1) Inland cliff lines (1) In context use of ages of beach sediments [3]

(ii) Sea level has risen (1 reserved) Peat (a terrestrial deposit) is now below present sea level (1) Submerged Forest (1) Relevant reference to beach pebbles(1) [2]

(iii) A : crustal depression (1) due to weight of ice (1) interglacial melting (1) isostatic readjustment (1) [3] B : (local) subsidence (1) +/- eustatic (explanation 1) rise (1) Due to (interglacial) melting (1) [3]

12 marks

21

Section B

3. "Topography is mainly controlled by the underlying geological structure". Discuss

this statement with reference to examples you have studied.

Credit to be given for field examples of landforms illustrating ideas

Dipping Strata

Cuesta (Downs)

Folds

Hills from anticlines (Pennines)

Mountains from core of synclines (Snowdonia)

Fold mountain chains (Himalaya)

Faults

Rift Valleys (Rhine, East Africa)

Faults as planes of weakness (Great Glen Fault)

Fault scarps (Wenlock Edge)

Thrust faults (Moine thrust)

Joints

Tors (Dartmoor)

Igneous Bodies

Plutons creating highland areas (Dartmoor, Mourne Mtns)

Volcanoes (Arthur's Seat, Deccan Plateau)

Resistant Rock

Monadnocks (Malvern Hills, Wrekin)

Coastal features

Credit given for other examples

22

4. Fossil material can be used to reconstruct Quaternary climatic change. Explain how this

material can be used to:

(a) determine the climatic fluctuations,

(b) provide a timescale for these fluctuations

(a)

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)

(b)

Timescale provided by dating organic material by 14

C dating

Small quantities of radioactive 14

C incorporated into living organisms from atmosphere

Decays over time

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 14

C

Zone fossils within Quaternary

Used for relative dating and correlation.

23

5. Compare and contrast the formation of two different types of limestone in terms of the physical,

chemical and biological processes that form them.

This mark scheme is based on Folk's classification. Others are acceptable.

Oolitic limestone

Description of ooids

Wave action of sea in warm shallow lagoon

Beach-dune barrier sediments

Calcareous precipitate from evaporation of seawater and algal secretions

High energy environment, relationship of ooid size and energy levels

Mostly fragmentary fossils

Micritic limestone

Carbonate mudstone

Precipitation in back-reef basin/lagoon with shallow marine fossils

Deposition as deep water muds with plankontic fossils

Well-bedded

Calcareous precipitate from evaporation of seawater and algal secretions

Low energy environment

Well-preserved fossils

Biomicrite/sparite

Coral limestone

Reef deposits containing corals and other fauna

Conditions for coral growth (temperature, depth, light)

Symbiotic relationship with algae

High energy

Chalk

Very high calcite composition

Remains of marine algae - Coccoliths

Frequently bioturbated. Burrows preserved with other fossils

Shelf deposition (100-600 metres deep)

Analogy with modern calcareous oozes

Other types of limestone (eg. Intramicrite) acceptable

Must have some comparison between types for access to full marks.

24

UNIT 2 - NATURAL RESOURCES

Q.1. (a) (i) Lack of cleavage (1) / high density (1) / cassiterite hard (1) [2]

(ii) Good cleavage (1) / soft (1) [2]

(b) Location - no mark

reduced energy conditions / speed of flow / affects

ability of water to transport minerals re. weight / density

(2 consistent points) [2]

(c) (i) chromite (1)

highest M.Pt. (1) [2]

(ii) Low(er/est) M.Pt. (1) / crystallises late(last) / low(est) density

means slower settling rate (1) and convection would tend to keep

olivine in suspension (1)

Any 2 as part of a consistent argument [2]

(iii) Bottom / base (1)

Chromite crystallises first (1) but is of lower density than

magnetite (1) and so is kept suspended by convection (1).

Temperature below 1600ºC will cause magnetite to form

which will settle due to greater density (1). When convection slackens

chromite and magnetite settle together (1). [3]

13 Marks

Q.2. (a) (i) 50 (+/- 5)ºC (1)

(ii) 40 (+/-5) Ma (1)

(iii) Breakdown of longer to shorter hydrocarbon chains (1)

Due to increasing T with depth / burial (1) [3]

(b) (i) Seismic (1)

(ii) Arrow (1) - to match explanation

Trap : salt dome (flanks) or anticline (crest) account accepted.

accept deviation drilling (1) [3]

(c) (i) Draw / Label (1)

Location : sandstone beneath unconformity (1) [2]

(ii) Hydrocarbons of low density (1) /

so migrate upwards (1) /

Collect in permeable reservoir rock beneath

impermeable cap rock (1)

Accept unconformity trap with matching explanation [3]

12 marks

25

Section B

3. With reference to one named non-metallic mineral of industrial value :

(a) Describe the geological processes responsible for its formation.

(b) Outline the stages in its processing from extraction to finished product.

(a) Examples : sand and gravel, clays(incl. kaolin), limestones, gypsum, talc, slate

etc.

Origins described : sedimentary / igneous / metamorphic processes which may

include reference to "purity" (if relevant) and accumulation of sufficient bulk for the

deposit to be economic.

e.g. Kaolin - (hydrothermal) chemical breakdown of (granite) feldspars.

Igneous environment.

Limestone - warm, shallow, clear, marine waters. Accumulation of

skeletal material (bioclastic / chalk). Water movement for oolitic.

(b) Stages to include (?) : (e.g.)

Kaolin : water jetting / settling tanks for use in paper, bone china etc.

Limestone : drilling, blasting - crushing / roasting to lime for (e.g.) cement.

- cutting / (polishing) to building stone.

26

4. Describe and explain the major geochemical techniques available to exploration

geologists in the search for mineral deposits. Outline the limitations of these methods.

Geochemical methods - definition

e.g. groundwater analysis, stream and lake sediments, soil and vegetation.

Description of techniques :

Water sampling : Identification of ions in solution - Cu, Pb, Zn, Ni, Sn, Fe.

Concentration in ppm

Study of above to locate source.

Soils : Samples taken to measure concentration of metals in regolith.

Dense, low reactivity not always removed by weathering and

erosion e.g. Sn, Cu.

High concentrations may indicate source at depth.

Sediments : Bedload of streams and from lake beds.

Heavy mineral concentrations by panning.

May indicate source upstream.

Vegetation : Vegetation ashed before analysis.

Some plants highly specialised in nutrient requirements.

[(Copper violet, California Poppy require) > 200ppm Zn or Au].

Limitations : Only thin surface layer sampled.

(Very) limited use (if any) in glaciated areas.

Remote areas. Laboratory facilities lacking.

Most useful as part of other investigations.

5. (a) Describe the geological conditions necessary for the accumulation of large-

scale coal deposits.

Description of coal-forming swamps / deltas. Credit examples.

Rate of supply of organic material exceeds rate of decay.

Rate of burial / subsidence / removal from oxidising conditions.

Peat-lignite-bituminous-anthracite progression re heat and C-content.

(b) Explain the environmental impact of coal mining and outline the ways

in which the impacts may be minimised.

Deep mining - subsidence

Open cast - land restoration

Spoil heaps - aesthetic

Methane

Effect on ground water

Legislation / planning controls

27

UNIT 3 - EVOLUTION Q.1. (a) (i) A = breccias B = dunes C = mud cracks 2 for 3 / 1 for 1 [2] (ii) Desiccation / mud cracks (1) = evaporation of water (1) within Zechstein Sea (1) [2] (b) Formed first : halite (1) Reason : less soluble / relative solubility (1) out of solution before K-salts (1) / sea shrinks (1) [3] (c) (i) L to R. [1] (ii) Dune bedding (1) / dip direction (1) of cross-beds (1) [2] (d) Palaeomagnetism / remanent magnetism (1) orientation of magnetic elements within volcanic rock (1) inclination into Earth indicates N-hemisphere (1) amount indicates latitude (1) [3] 13 Marks Q.2. (a) (i) Parallel fold axes (1) [1]

(ii) Affects older rocks / not affect younger rocks (1) Fold axis stops at unconformity / younger rocks / P / J (1) [1]

(b) Fold : M (1) Evidence : younger rocks(1)along the axial plane trace(1) Alpine Orogeny "recent"(1) [3] (c) trace (1) correct symbol (1)

[2] (d) Younger than Carboniferous (1) Cannot be more precise (1) [2]

(e) Explanation : Igneous rocks / granitic plutons related to DPM (1) Plutons due to (mechanism) subduction (1) /

(partial) melting (1) / continental crust involved (1) / differentiation etc (1) Knowledge based account e.g. metamorphism etc of Lizard discussed (up to 3) [3]

12 Marks

28

Section B

Q.3. A sequence of rocks contains quartz sandstones with ripple marks and well-preserved

trilobites, and limestones with brachiopods and corals. It has been suggested that this

sequence was deposited in shallow, warm, marine conditions. Evaluate the validity of

this suggestion.

Quartz sandstones : consistent with beach / shallow water

but : not specific e.g. desert sandstones and no indication of temperature

Ripple marks : no indication of symmetry / suggests shallow water

but : could be aeolian / any depth water / no indication of

temperature

Trilobites : marine

might be shallow / features ?

but : extinct so no certainty

not indicate temperature

well-preserved = calm conditions (only) or rapid burial

Limestones : suggest warm, shallow marine conditions

but : other environments e.g. deep-water chalk

Brachiopods : suggest warm, shallow marine conditions

but : some species could tolerate deeper, colder waters

Corals : good indicator of warm, shallow marine conditions

but : species could tolerate deeper, colder waters

Conclusion : taken together features strongly indicate warm, shallow, marine conditions.

Particularly if the Law of Uniformitarianism is applied. However, it is necessary to consider

the objections given above.

29

Q.4. Discuss the evidence which suggests that Britain once lay close to the equator. Comment on the reliability of the evidence.

Britain drifted north across the equator during the Late Palaeozoic. Palaeomagnetic evidence relies on the inclination of the remanent magnetism. Should be zero when at the equator. Up to the Late Palaeozoic inclination is consistent with Britain being in the southern hemisphere. After the Late Palaeozoic inclination indicates northern hemisphere. The evidence may also be used to build up a picture of how continents and supercontinents behaved in a plate tectonics context. Effects of orogenesis on the Britaish Isles. Examples of changing climates as indicated by differing rocks and fossils. (Opportunity to consider Late Palaeozoic rocks and fossils in detail if they have been studied). The use of palaeomagnetism gives a consistent picture and results correlate well around the world. Most effective with fine-grained basic igneous rocks. May be possible to use the technique with sedimentary and igneous rocks. Need to apply a scientific approach as there may be individual anomalous results. Lithological and palaeontological evidence is usually reliable but may be open to more than one interpretation. Evidence would be consistent with Britain moving towards the equator and then back again. Alternatively, the global climate may have changed in such a way as to produce the evidence (found in Britain). Taken altogether evidence points to a northward drift of Britain across the equator.

Q.5. The Tertiary Igneous Province of northwest Britain provides evidence of the early

history of the opening of the North Atlantic Ocean.

(a) Describe the nature of the evidence, and (b) Discuss the validity of the above statement.

(a) Volcanic and intrusive igneous activity

Dyke swarms + significance re stress pattern Igneous / plutonic centres + significance re stress pattern / rifting Lavas Examples Ages of igneous rocks compared to age of N.Atlantic ocean floor

(b) Above related to CPM re tension, basaltic igneous activity

Dyke swarms re stress pattern and tension / rifting Plutonic centres as sources of lavas - centres mafic and silicic / differentiation? Lavas / flood basalts / possible relationship to sea-floor spreading

Accept detailed consideration of one example re. fieldwork e.g. Arran.

30

UNIT 4 - LITHOSPHERE

Q.1.

(a) (i) Similarity Parallel or same (1) / (N-S)strike or trend (1)

steep dip (1) / dip in opposite directions (1)

Difference A dip in / B dip out (NOT dip in opposite direction)

A reverse / B normal (1)) [2]

(ii) as above : (2 for 3 / 1 for 1) [2]

(iii) B (1)

Formed due to tension(1) (min horiz / max vert)( 2)

Similar conditions at MOR (1) / extension (1) [3]

(b) DPM = Compression(1) / collision (1) / Reduction in length of crust (1)

Folding(1) (usually with qualifications up to 3) associated with

compression (1) [3]

(c) Conservative PM = shear (1) / no extension or shortening etc (1) [2]

12 marks

31

Q.2. (a) (i) Rock sequences / layers very similar(1) [1]

(ii) P-wave velocities lower in ophiolites (1) [1]

(b) M between L3 and L4 (1)

Change in P-wave velocities / mineralogy (1) / qualification (1). [2]

(Accept between layered and unlayered peridotite as mineralogical Moho)

(c) (i) Mark on Figure 2(b) with an arrow labelled O (1 Reserved)

Plate movement(1) / DPM(1) / subduction (1) / obduction(1) / density

difference(1) (3)

(ii) Mark on Figure 2(b) with an arrow labelled X (1 Reserved)

Youngest lithosphere (1) / "no" time (1) / "no" clastics (1) /

pelagics (1) (3)

(d) Metamorphism(1) / temperature increase(1) / magnetism destroyed(1)

Recrystallisation (1) iron minerals reorientated (1)

Accept other types of meta e.g. dynamic / shearing or chem. / hydrothermal

activity (3)

13 marks

32

Section B

3. Compare and contrast continental and oceanic lithosphere in terms of :

age,

structure, and

composition.

Similarities : Base of lithosphere = 1300degC isotherm

Lithosphere = zone above asthenosphere

Lithosphere = crust and upper mantle

Movement

Continental Oceanic

Thicker 35 to 60km Thinner 5 to 10km (CPM to DPM)

Granitic / equivalent Mafic / basic

Less-dense (not subduct) More dense (subducts)

Sedimentary, igneous and metamorphic

rocks

Layered / 1, 2 and 3 (sediments, pillows,

dykes and gabbros)

Older < 4.2Ga

Tends to be older in"middle" with

vertical stratigraphy / Law of

Superposition

Ridge / abyssal planes / trenches

Younger < 200Ma

Older away from ridge / horizontal

stratigraphy

(May be) folded and faulted ("all" types) Transform faulting common

Spreading

Magnetic striping

Orogenic belts / cordillera Island arcs

4. Discus the extent to which the J Tuzo Wilson cycle of ocean formation and destruction

is supported by the present-day size, structure and distribution of oceans.

(Probably) With reference to Pacific and Atlantic re. sizes and structures.

(Continental splitting rifting e.g. E African)

Ocean formation opening of an ocean basin e.g Red Sea to Atlantic

central ridge MAR

passive margins on each side getting bigger / wider

subduction begins at margin(s)

Closure Pacific / trenches

getting smaller

marginal ridge EPR

Thus one growing whilst other shrinks

(Orogeny where collision occurs)

Conclusion

33

5. Discuss the use of seismology in the distinction between the lithosphere and

asthenosphere. Comment on the possible significance of temperature in the formation

of the asthenosphere.

Seismology = use of P, S and L-waves.

P and S velocity depends upon properties of medium through which they are passing.

Discussion of properties = shear and bulk moduli plus density.

Velocities directly proportional to (square root of) moduli; inversely proportional to

density.

Variation of velocities with depth.

Recognition of a low-velocity zone - 0(?) - 250km depth.

Deeper under continental lithosphere.

Shallower under oceanic lithosphere.

Suggests a semi-molten state.

Corresponds with 13000C isotherm = partial melting of mantle.

Correlation of lower velocity with partial melting.

Low-velocity layer synonymous with asthenosphere.

(Diagrams of seismic wave paths and geotherms).

GCE M/S (June 2004)/Geology/JD

Welsh Joint Education Committee

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