WELSH JOINT EDUCATION COMMITTEE

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WELSH JOINT EDUCATION COMMITTEE
CYD-BWYLLGOR ADDYSG CYMRU
General Certificate of Education
Tystysgrif Addysg Gyffredinol
Advanced Subsidiary/Advanced
Uwch Gyfrannol/Uwch
MARKING SCHEMES
SUMMER 2007
GEOLOGY
INTRODUCTION
The marking schemes which follow were those used by the WJEC for the 2007 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.
GL1
1.
(a)
(i)
Layer of
ocean crust
Rock type
Name of igneous
structures
Q
 Basalt

Pillow lavas
R

Dolerite

Dykes
S

Gabbro
[4]
(ii)
(iii)
(b)
(i)
(ii)
(c)
Plagioclase feldspar
Pyroxene or Augite
Olivine
2 of these
[2]
More rapid cooling causes finer crystal size (or equivalent) (1)
More rapid cooling closer to the surface (or equivalent) (1)
Contact with seawater (1)
Rapid cooling/quenched (1)
Forms a crust/skin (1)
Inflation/pushing through the pillow or equivalent (1)
(any two)
Partial melting or equivalent (1)
Of mantle/asthenosphere (1)
Of ultramafic/peridotite (1)
Lower melting temperature components melt (1)
Credit other valid point (1) e.g. pressure release
(any three)
(i)
Points plotted showing positive correlation
(ii)
Correct relative age of crust e.g. B older than C (1)
[2]
[2]
[3]
[1]
Correct reason for relative age of crust (1)
Thicker sediment = older. (I.e explicit statement of age thickness
relationship) (1)
Because longer time for sediment accumulation/ will not have had as
much sediment on it (1)
Credit link to sediment derived from the continent. (1)
(any three)
[3]
Total 17 marks
1
2.
(a)
(i)
Age relative to something else/ older:younger (1)
[1]
(ii)
Intrusion is younger than Carboniferous rocks because it cuts them or
equivalent (1)
Intrusion is older than Quaternary sediment because they overlie the
intrusion or equivalent (1)
[2]
(b)
(i)
Gaseous exchange between tree and atmosphere (1)
[1]
(ii)
Decrease in the amount of 14C. (1)
14
C decays radioactively (1)
14
C not replenished from the atmosphere (1)
[3]
(iii)
Fossil
tree
Quaternary
sediment
in
Fossil
tree
in
Carboniferous
sedimentary rock
Igneous intrusion
Suitable for
dating by
14C method.
Yes/No
Yes
Reason(s)
Organic matter
(1)
Young enough/not too old
(1)
No
Too old (or stated age 350-275mya)
so that too much 14C is lost (1)
No
Not organic
3 correct = 2 marks
2 correct = 1 marks
1 correct = 0 mark
(1)
[6]
Total 13 marks
2
3.
(a)
J located in the shale outside the metamorphic aureole (1)
[1]
(b)
During folding (1)
Under NE-SW compression (1)
(R one of these two as a link to Fig 3b)
Regional metamorphism (1)
Low grade (1)
(heat and) pressure 1)
Of a fine grained/or named fine grained sedimentary rock (1)
Aligned grains (1)
[3]
(c)
(i)
(ii)
(d)
(e)
shorter wavelength/ more intense in slate (1)
or vice versa
trend of axial plane trace NW-SE in slate
but NE-SW in shale (1)
[2]
NW-SE (1)
[1]
Downthrow to SE because:
Younger rock on downthrow side (1)
Shale is unmetamorphosed (1)
[2]
specific type of fold/fault e.g. "reverse fault", "anticline" (1)
Quality of diagram/description (2)
Reference to appropriate scale (1)
Specific location of feature (1)
Correct name of stress involved (1) R
e.g. Extension/Tension for normal fault,
Compression for reverse/thrust fault or fold
Shear for tear fault
3
[5]
Total 14 marks
4.
(a)
(b)
(c)
(d)
(e)
(i)
Trilobite (1)
[1]
(ii)
Glabella (1)
[1]
Brachiopods have:
2 different sized valves/inequivalve (1)
plane of symmetry within 1 valve/equilateral (1)
pedicle foramen or pedicle (1)
diductor muscle scars (1)
or equivalent
Bivalves have a pallial line/sinus (1)
2 of these
[2]
Soft parts absent (hard parts only present) R (1)
Decay/decomposition/eaten/eroded/breakdown (1)
[2]
Solution of calcite (1)
Any ref to groundwater/ porewater/percolating water (1)
Quartz/silica precipitated /crystallised (1)
Replacement (atom by atom)/Impregnation/Petrifaction (1)
[3]
(i)
(ii)
(iii)
Not preserved in life position (2)
Moved/ transported (1)
after death or before preservation (1)
[2]
Valves fragmented/disarticulated/separated (1)
damaged
Due to transport/current etc (1)
Not in life position(1)
[2]
1 for statement of environment (1)
e.g. high energy bed 1/low energy bed 2/fast deposition bed 2
1 for evidence (1)
e.g. fragmented in bed 1/whole in bed 2/well preserved bed 2/flipped
in bed 1
at least 1 for cause of change (1 R)
e.g. – may indicate deepening water over time (1)
– may indicate sudden high energy current event during bed 1
deposition (1) )
[3]
Credit other relevant answers
Total 16 marks
4
GL2a
SPECIMENS
A
=
granite (for use in Q1)
B
=
calcite (for use in Q2)
C
=
schist (for use in Q3)
1.
(a)
(i)
(ii)
(iii)
(b)
(texture only)
crystalline
porphyritic
1
1
2
cooling and crystallisation of a magma
2-stages (larger phenocrysts first)
1
1
2
TWINNING or CLEAVAGE is the only property which can
gain the following marks:
 description (e.g. use hand lense to see any regular 1
breakage/twinning)
1
 none seen in grey mineral (accept fracture)
1
 present in pink/white mineral
Photo 1
either (D) chilled margin
(E) finer crystals than in Specimen A due to rapid
cooling against cold country rock
or
(D) dyke/vein
(E) a melt intruding weaknesses in cold, brittle country
rock
Photo 2
(D) random chiastolite/andalusite crystals
(E) contact metamorphism of cold country rock as hot
melt cools
Map 1
(D) radial dip
(E) forceful intrusion domes country rock
5
3
1
1
1
1
1
1
1
1
6
(13)
2.
(a)
scaled drawing
shape of ooliths
structure of ooliths
pore spaces
1
1
1
1
4
1
1
(b)
(i)
(ii)
positive acid test or rhombic cleavage
Calcite
1
1
(c)
(i)
non-frilled, showing lobes and saddles
(e.g. "zig-zag", "angular", "rounded")
Upper Palaeozoic
Goniatitic (or similar e.g. early type of suture evolution)
1
1
1
1
(No mark for evaluation only; mark reason only if evaluation is
correct)
Photo 3
False
 limestones/ooliths form in shallow marine environments
Photo 4
Correct
 fossil group (cephalopod/ammonoid/goniatite)
 uniformitarianism (nautiloids) R
1
(ii)
(d)
2
2
1
1
3
(13)
3.
(a)
(i)
e.g. freeze-thaw
1
1
(ii)
water expands in cracks as it freezes
cyclic process
1
1
2
Textural – foliation/aligned crystals
Mineralogical – micas or garnets
1
1
2
(i)
b/a = 0.80
1
1
(ii)
plot and label the answer from part (i)
1
1
(iii)
foliation causes "thin" fragments when physically weathered
1
1
(iv)
spheres
1
1
(v)
plutons/granites have cooling joints
3-D spacing produces “cubic” fragments
1
1
2
(b)
(c)
c/b = 0.12 or 0.13
(11)
6
4.
(a)
(i)
horizontal rock overlies folded rock units/ cross-cutting
1
1
(ii)
e.g. weathered surface beneath Rock Unit
e.g. included fragments of older rocks (C, E, F) in Rock Unit B
1
1
1
NE-SW line within Rock Unit C, but not cutting through the
unconformity
1
1
(i)
25m
1
1
(ii)
F1 downthrows to the southeast
F1 is normal
1
1
2
F2 is vertical (straight line of outcrop)
Dowthrows to northwest, but is this the hanging or footwall?
1
1
(a)
see section
10
10
(b)
see table
5
5
(15)
(b)
(c)
(iii)
5.
7
2
(8)
radial dip around the
pluton

B base at 250m

symmetrical
antiform fold

edge of pluton

F2 dip

movement
Antiform fold
axis

F1 dip

movement
top & base of
Rock Unit E
either to west
of F2 or east
of
F1

both A
correct
and
 superficial deposits

 F2

D


 folding
both F and C correct

 folding
(alternative)

8
9
GL3
1.
(a)
Arrow (1R)
Glacial till impermeable – sandstone permeable (1)
– water forced to the surface.(1)
(2 max)
[2]
(b)
Rotational slip plane in tip debris.
(c)
(i)
(ii)
(d)
(e)
[1]
Loading, groundwater (spring), rainfall, lithology,
angle of slope (not dip), vibration, other (any 2)
[2]
Geological factor explained
[2]
Monitored for creep, strain, groundwater pressure,
Mapped for spring presence.
Slope stabilisation, methods – drainage, diversion etc
(3 max holistic)
[3]
Stability of rock faces, rock falls, ground subsidence,
gas explosions, flooding, surface/groundwater pollution
(2 max)
[2]
Total 12 marks
10
2.
(a)
(b)
(c)
As Richter scale increases
energy increases (1) and frequency decreases (1)
Credit use of numbers
(2 max)
[2]
(i)
32 million
[1]
(ii)
Rare for energy to build up so high before slipping
build up if strain takes time .
(2 max)
[2]
(i)
Name
Earthquake A
Earthquake B
Distance
(km)
~50
S-P lag time
(seconds)
6
(25-27)
~225
25
Aftershock C
Amplitude
(mm)
0.2
Richter
Magnitude
2
20
5
2
4
Care with follow on
(ii)
(d)
[3]
1. 32
2. 10
[2]
Increase/decrease in background rate of minor quakes
Seismic Gap.
Measurement of P and S velocities passing through fault zone.
Reduction indicates influx of water into rock as micro-fractures open.
On returning to normal, pore pressure rises = quake.
Duration of anomaly = predicted magnitude of quake.
Holistic (3 max)
[3]
Total 13 marks
11
Section B
3.
(a)
Describe the properties of rock that control porosity and permeability in aquifers.
Aquifer, permeability, porosity (specific yield) defined.
High POROSITY depends upon gaps between grains large/interconnected
Primary and secondary porosity depends upon
Packing of grains – cubic v rhombic
Fracture/joint spacing
Shape/orientation of grains – angular v rounded
Sorting of grains – small fit in between larger.
Cementation
PERMEABILITY depends upon
Connectivity of pores
Size of pores
Joints and fractures
Interconnected joints, faults, fractures, solution cavities
Examples – Limestone, sandstone, fractured/jointed igneous and met rock
Credit structures if related to permeability (artesian basins/confined/unconfined
aquifer). Good aquifer depends upon good permeability/specific retention.
Case studies given credit.
[10]
(b)
Explain how geologically related problems may result from interference with
the hydrological system.
Holistic – may include:
1.
2.
3.
4.
5.
Local exhaustion of water table – cones of depression.
Extraction exceeds recharge.
Reduction of flow from springs/wells – dry wells and valleys
– loss of wetland habitat/domestic supply in arid region.
Loss of artesian effect.
Flooding if hydrological system is blocked/throughflow restricted.
Reduction in pore pressure causing surface subsidence.
Contamination as pollutants are drawn in – pollutants identified.
Sea water contamination in coastal areas
Examples (e.g. London) and diagrams credited.
Acid Mine Drainage – mining
Reference to interference with coastal processes – longshore drift,
coastal erosion/deposition.
Pumping water into faults – earthquake reactivation – Denver, building
reservoirs increases pore pressure and instability – Vaiont dam
[15]
Total 25 marks
12
4.
(a)
Using one or more case studies, describe how one of the following volcanic
phenomena can be hazardous:
(i}
(ii)
(iii)
lahars
volcanic gas
blast/explosion
lahar
Reworked ash from volcano. Melted snow and torrential rain.
Hot, liquid. Consistency of concrete – fast flowing.
Suffocation/drowning/burial.
Difficult to predict. Lasts for years.
E.G. Armero(Columbia)/Pinatobo etc.
volcanic gases
Variety – CO2, H2S, CO, SO2 etc – contain fluorine, sulphur, chlorine –
noxious
Hot (1000C) – Suffocation/drowning/burial/burning/respiratory problems
Effect on vegetation. – Not affecting buildings but kill people – silent killer
E.G. Lake overturn – Lake Nyos – Cameroon.
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 10 – No case study – max 7)
(b)
Explain how the risk to life and property associated with a major volcanic event
largely depends upon the extent to which an eruption can be predicted or its effect
minimised.
Holistic approach
Volcanic hazard defined – i.e. Risk of the harmful effect to human life or
property of an unavoidable volcanic event.
Minimising volcanic hazards and efficient/effective prediction reduces the risk
and scale of the potential hazard.
Minimising may involve – evacuation, hazard mapping, diversion/blocks,
dropping-spraying with water, explosion of flow margin.
Case studies credited – Iceland, Etna.
Prediction may include – monitoring ground deformation, gravity and thermal
anolalies, gas emissions and seismic activity (harmonic tremors).
Effectiveness discussed and case studies given credit – Pinatubo.
Ultimately always risk of hazard if people choose to live near volcanoes.
(Max 15 to include evaluation – 12 max if none)
Total 25 marks
13
5.
(a)
Compare the changes in radon gas emissions before and after an earthquake
with the changes in groundwater levels (identified in wells) over the same
period of time. Explain your answer.
During build-up of elastic strain prior to earthquake (dilation) cracks open –
radon released and increase recorded. Water levels fall.
Radon gas emissions stabilise in diffusion stage where no new cracks open.
Water levels rise as water infills cracks. (Credit also – Radon gas increase also
associated with the movement of groundwater into the micro-cracks as it is
soluble in water.)
Fall to background levels after quake when micro-cracks close. Water levels
rise further.
(Max 10 marks)
(b)
Account for the presence of high radon gas concentrations in some buildings
located in particular areas of the British Isles.
You should consider

the sources, and pathways of the gas to the surface,

the surface geology in high risk areas and

the risk involved in high concentrations.
Radon defined. A dangerous (when in high concentrations) inert gas from
decay of uranium rich rock.
Natural release from radioactive decay.
Sources and pathways. – porosity, permeability examples.
Granite – high risk areas (SW England). Other areas associated with
shale/limestone.
Radon dissolves in water and transported in groundwater.
Released when pressure drops/near surface.
Trapped by some rock types (clay) but released to atmosphere to be trapped by
poorly ventilated/well insulated buildings (cellars, attics, roof and floor voids).
(Max 15 marks)
Total 25 marks
14
MARK BAND CRITERIA FOR AS ESSAYS.
Summary
Description
Mark out of
25
Excellent
21 - 25
Good/Very good
16 - 20
Modest/Quite
Good
11 - 15
Weak/Minimal
6 - 10
Very weak
1-5
Criteria
Not the perfect answer but purposeful,
demonstrating a secure grasp of knowledge and
understanding and few significant omissions.
Well-supported and illustrated with detailed
examples selected from named geological
situations. Ideas expressed fluently in logical form
using appropriate geological terminology. Few
errors in grammar, punctuation and spelling.
Sound answers with relevant material providing
evidence of good knowledge and understanding.
May be limited in terms of supporting material and
breadth of coverage but appropriate examples
selected. Ideas expressed with clarity with only
occasional errors in grammar, spelling and
punctuation.
A reasonably secure grasp of basics but some
deficiencies in knowledge and understanding
although use is made of geological terminology.
Examples and illustrations may lack detail or may
not relate to real geological situations. Reasonable
use of language with adequate spelling and
punctuation.
Answers show limited basic knowledge and
understanding, lacking directness and organisation;
tendency to rehash prepared material and answer
by inference.
Superficial use of examples.
Deficiencies in use of language evident;
weaknesses in spelling and punctuation apparent.
Little evidence of knowledge and understanding
with erroneous or repeated material evident.
Candidate is unable to address the question.
Largely irrelevant; possibly too brief. Language
skills poor, with spelling, grammar and
punctuation errors becoming obtrusive.
Incorporated into this mark scheme is the assessment of candidates on their ability to organise
& present information, ideas, descriptions & argument clearly & logically, taking into
account their use of spelling, punctuation & grammar.
15
GL4
1.
(a)
(i)
Bivalve (1)
[1]
(ii)
Laminated (1)
Clay minerals (1) fine grained (1)
Name: Shale (1)
[3]
Marine/low energy/near land (1)
Marine – cephalopod/marine fossil (1)
Near land – plants washed in (1)
Low energy/deep – fine grained/clay (1)
[3]
Contact/thermal met only /high temp/heat/intrusion (1R)
(don’t credit heat if in conjunction with pressure)
– lacking pressure/no cleavage/foliation (1)
(Random) Chiastolite crystals/growth of new
minerals/spotted rock (1)
Fossils destroyed/lacking (1)
[3]
Regional met/Temp & Pressure/Orogenic processes (1)
Shale to slate (slatey cleavage/relic cleavage) (1)
Then later (1R)
contact met/intrusion/high temp (1) - Random chiastolite
which cuts cleavage (1)
HOLISITIC
[4]
(iii)
(b)
(c)
Total 14 marks
16
2.
(a)
(i)
Fault
characteristics
Strike direction

N-S
Dip (degrees)

90
Throw (vertical
displacement)
Principal stress
direction (σ
max)
Type of fault
Description
0 (zero) metres

SE-NW

Sinistral/strike
slip/wrench/tear/transcurrent
[4]
(ii)
(b)
(c)
Scratches/grooves show orientation of movement (1)
May not indicate actual direction (1) unless
Smooth feel in downslip direction (2)
Possibly indicates last direction of movement. (1)
Horizontal in fig 2a (1) (2 max)
B (1)
Fault breccia (1)
Contains igneous material not likely at A/clasts of all rock types
Unless reactivation(1) – A then accepted(1)
(Accept explanation of why not C or D)
(i)
(ii)
Dyke/discordant/igneous intrusion not lava flow/
concordant (1R)
Other medium grained not fine as in lava flow
size too small,
controlled by joints/too regular
no sag structures/spherical not pillow shaped
(2 max)
[2]
[3]
[3]
Water along joints
Chemical decay (rot/breakdown of feldspar to clay) of the
minerals/oxidation, hydrolysis etc
Greater at the joint boundaries – larger surface area
Rounding to produce core stones
[3]
Holistic
Total 15 marks
17
3.
(a)
(b)
(c)
(d)
Viscosity increases (1) with increase in SiO2 %age (1)
Positive relationship (1)
(2 max)
(i)
[2]
Similarity
Both melts are less viscous at higher temperatures
(melts more viscous at lower temps) (1)
Difference
Granite magmas are always more viscous
than basaltic magmas at any temperature. (1)
Granite increases/decrease faster (visa versa) (1)
[2]
(ii)
1100 oC (1)
[1]
(iii)
Lower temp & higher viscosity range
than basalt (1)
Higher temp & lower viscosity range
than granite (1)
[2]
Basalt is non viscous (runny).
Extruded hot, with low SiO2 content,
Gas is readily able to escape in bubbles.
Flows further before it cools.
Runs in tunnels (lava tubes) many kilometres –insulated.
Holistic(3 max)
(i)
(ii)
[3]
Subduction of ocean lithosphere (basalt) at trench (1)
Seawater dragged down (seawater within sediment)
with descending plate(1)
(max 2 marks)
[2]
Lowers the melting point (1)
Allowing magma to be generated at shallower depths (1)
Lower temperatures of magma (1) More explosive
eruption (1)
(max 2 marks)
[2]
Total 14 marks
18
4.
(a)
All true (1) but pygidium smaller than cephalon (1R)
(b)
(i)
[2]
Large eyes positioned on side – 360o vision (below) (1)
Streamlined body – fast movement or equivalent (1)
Limbs – paddles (1) Spines – stability in water/protect rear (1)
Inflated glabella – buoyancy (1)
(2 max – 1 if only described)
[2]
(ii)
Morphological
feature
Genal spines
Fringe on the
Cephalon
(d)

Help to stabilise during feeding /channel water
towards fringe
Used to create a water current to allow food to
be drawn towards mouth
NOT: propulsion/swimming
Filter food from water/shovel for
burrowing/large surface area so more food can
be gathered
Credit other sensible
[3]
Can’t really use uniformitarianism
Extinct group – no current forms that have similar
morphology to study
Exceptional preservation (example: eg. Burgess Shale,
Solnhofen Limestone etc) allows soft parts preserved
Credit trace fossils for morphology/behaviour
Holistic (3 max)
[3]
(i)
(ii)
(e)


Limbs
(c)
Possible function
Constant/steady increase/straight line (1)
in morphology with time (1)
No stasis (1) (max 2)
[2]
Stepped line (1)
Stasis labelled (1)
[2]
Fossil record is biased – rarely preserves soft parts
Limited preservation - predation, scavengers, diagenesis
Missing links may not be preserved .
Fossils may not be representative of actual population
Trilobites old - Palaeozoic age but hard shell preserved
Trilobites not known to show major evolutionary changes
Sample may not be valid/ representative
Grapt/amm/gon/cer/horse examples (Max 1)
(Holistic – max 3)
[3]
Total 17 marks
19
Section B
5.
(a)
(b)
(i)
Head (1)
[1]
(ii)
Narrow, linear, dimensions (1km max, 300m min), N-S
(max 2)
[2]
(i)
[4]
Formation
Wyche Formation
(Wy)
Dip direction
West (WSW)
Apparent dip angle (degrees)
75 (80-70) degrees
Rock type (Igneous, sedimentary
or metamorphic)
Age
sedimentary
(ii)
(iii)
Silurian
Malverns
Complex
(MvC)
None
None
Intrusive
igneous
Precambrian
No metamorphic/baked margin/aureole
Included fragments
Precambrian MvC older than Silurian Wyche
(max 2 marks)
[2]
unconformity (1)
[1]
Total 10 marks
20
6.
(a)
(i)
Rising (1), levelling (1), accuracy (1)
[3]
(ii)
PT lower density – lower gravity
Silurian higher density
thicker sequence – lower gravity
effect of faulting explained
link to geol struct (isogals parallel to outcrop)
(3 max)
[3]
Total 6 marks
21
7.
(a)
Fold characteristic
Fold type
Description

Syncline/synform
Fold symmetry

Asymmetric/numbers
Orientation of
axial plane trace
Plunge direction

NNW-SSE (N-S)

South
[4]
(b)
(i)
(ii)
55mm *10 (5.5cm* 100) = 550m
(1) method (1)
(Range: 530m-570m and correct working)
[2]
Similar dips to East (1)
CF = Reverse movement (crustal shortening) (1)
EMF – Normal (crustal extension) (1)
Probably not contemporary/at same time – opposite stress
fields (1)
Credit fault reactivation arguments
(max 4 marks)
[4]
Total 10 marks
22
8.
(a)
(b)
Joints/fractures/faults make it permeable(1R)
High relief provides rainfall (1)
Springs where water forced to the surface (1)
At faults/unconformity/joints/fractures.
(Max 2 marks)
(i)
(ii)
[2]
Steep dipping mudstone/siltstone (Coalbrookdale)
lmst (Woolhope)
mudstone/siltstone (Wyche)
List of rocks (not age) : max 2.
Massive igneous (Malverns)
Low dip mudstone (Mercia)
Faults (three -four).
Small made-ground/drift
(max 4 marks)
[4]
Water problem in permeable strata
Fault reactivation – water along fracture
Igneous rock/lmst – strong/more difficult to work/but less
support needed
Mudstone/made ground – weaker/easier to work/needs
support
Wy Wyche overturned strata/steep dip – need support
(Holistic max 4)
[4]
Total 10 marks
23
GL5 THEME 1 – QUATERNARY GEOLOGY
Section A
1.
2.
(a)
(i)
West of Andros Island (1) length of the island (1) shallow water (1)
shelf (1) (distances and latitudes / longitudes credited)
(ii)
Low energy (1) allows fine sediment to be deposited (1) warm (1)
shallow sea (1) evaporation and precipitation (1)
(b)
High energy(1) nutrients brought by ocean currents(1) photic zone (1)
oxgen (1)
(c)
(i)
Concentric structure (1) nucleus (1) to scale (1 reserve)
(ii)
HOLISTIC : carbonate precipitating (1) confined to depths less than
180m(1) in higher energy environment (1) wave action moving the
grains(1) flow depositing ooids in cross-beds (1)
(a)
2 of : Moraine / till present (1) corrie (1) ice-scratched rocks (1) arête (1)
pyramidal peak (1)
(b)
(i)
Eroded basin of corrie (1) impermeable till / bedrock (1) + (1) for
development
(ii)
2 periods of glaciation (1) terminal (1) recessional moraine (1)
(i)
High on the mountains (1) above 700 m contour (1) south-facing
slope (1) edge of frost-shattered boulders (1) E-W (1) to the north (1)
(ii)
Melting of frozen soil (permafrost) (1) on slopes exposed to sun (1)
weakened soil flows down the slope (1) saturated (1)
(c)
(d)
Holistic mark for argument. Reference to time (1 reserve) ice in Cwm Cau
with periglacial conditions higher than ice limit or periglacial conditions
existed whenice had melted as climate ameliorated. High up because of steep
slopes and more rain.
24
Section B
3.
(a)
Explain how Milankovitch Cycles are thought to cause climatic fluctuations in
the Quaternary.
Eccentricity/Precession/Tilt - descriptions including diagrams
Effects on seasons
Combined - effects on climate
Cyclical nature of climate change
(b)
Discuss the importance of the distribution of continents and mountain belts in
influencing global climate in the Quaternary.
Position of continents affects oceanic circulation (and atmospheric)
Particularly with reference to Quaternary positioning in N hemisphere
Mountain belts (particularly Alpine-Himalayan) affect atmospheric circulation
Recognition of other factors - Milankovitch Cycles; solar activity; volcanic
activity etc.
4.
(a)
Explain how fossils can provide evidence for Quaternary climatic fluctuations.
Consideration of one or more (breadth versus depth) of the following :
Pollen & vegetation community reconstruction
Beetles
Mammoths and other vertebrates – use of adaptation to climate
Foraminifera and oxygen isotope data
Tree ring climate data
(b)
Evaluate the use of radiocarbon (14C) dating in determining the duration of
Quaternary climatic fluctuations.
Absolute dating
Can only date organic material
5,730 half-life
Can only date recent events accurately
Limited use during glacials – lack of dateable material
Cannot be used for much of the Quaternary period
5.
“Geological structure and lithology of an area controls drainage patterns of water
both above and below the surface.” Evaluate this statement with reference to
examples you have studied.
Effects of structure and / or lithology in production of :
Radial drainage (domes, volcanoes etc)
Trellised drainage (dipping rocks, basin & range etc)
Dendritic drainage (homogenous geology)
Superimposed drainage
Dry valleys
Groundwater flow (aquifers, aquicludes etc)
Subterranean river courses
Springs
Breadth versus depth but must cover surface and groundwater
Credit use of examples
25
GL5 THEMATIC UNIT 2 – NATURAL RESOURCES
Section A
1.
(a)
(b)
2.
(i)
oval or disc shaped (1) concentric structure (1) layered/bedded (1)
bowl / basin (1) use of scales (1)
(ii)
Calcite (1)
First to precipitate from solution / least soluble (1) forms the lower
layer (1)
Only 50-60% of seawater volume needs to be evaporated (1)
(i)
Tides (1) storm (1)
(ii)
5 cm ≡ 3 metres
100 cm (1 metre) ≡ 20  3 = 60 metres
200  60 = 12,000 metres
(iii)
Repeated sequences (of replenishment, evaporation, precipitation) (1)
followed by subsidence (due to mass of accumulated evaporites)
(1 reserve)
(c)
Atlantic too deep - unable to evaporate >60% of volume to commence
precipitation from solution (1) climate too cool - rates of evaporation low (1)
conditions (e.g., turbulence) unsuitable (1) lack of suitable environments for
playa formation (1)
(a)
(i)
S = Base of Chalk-junction with Gault Clay (1)
A = Any location vertically through the Lower Tertiary to Chalk (1)
(ii)
Synclinal structure (1)
Impermeable Gault Clay beneath (1)
Chilterns and N Downs chalk outcrops at surface acts as unconfined
aquifer (1)
higher ground - more rainfall (1)
(b)
Discussion of the following in correct context re porosity (space) and / or
permeability (interconnection). BOTH discussed for 3 marks :
Coccoliths - disc shaped with holes in centres. Loose packing / compaction of
coccoliths. Joints / bedding planes / faults.
(c)
(i)
(25 to 26)  (11 to 12) = 13 to 15 metres (or use of scale)
(ii)
Chalk acts as a natural filter and has fewer suspended particles (1) less
treatment is required (1) stored at a stable temperature, low oxygen
levels, surface waters vary in temp (1) reservoir water more likely to
contain contaminants that need treatment such as chemicals / nitrates /
other pollution sources (1) organic matter/algal blooms, etc., in surface
reservoirs (1)
26
Section B
3.
"Igneous processes are the most important processes in the formation of epigenetic
and syngenetic mineral deposits."
Evaluate this statement and illustrate your answer with reference to examples you
have studied.
Igneous processes – related to cooling and solidification of magma/lava and
pyroclastic activity
Explanation of syngenetic - formed at same time as enclosing rock
Explanation of epigenetic - formed later than enclosing rock
Processes (case studies ) one or more (breadth versus depth) of :
- cumulate/gravity settling
- pegmatitic
- porphyry copper
- pneumatolysis
- metasomatism
- hydrothermal
- black smokers
- kimberlites
Description of processes with links to the actual minerals being formed: cassiterite,
galena, sphalerite, diamonds, chalcopyrite.
Description of form of deposits – veins, lodes, reefs, stockworks
Other processes – surface processes/sedimentary part of the rock cycle. Weathering
and residual deposits, placer deposits, evaporites, supergene enrichment. Formation of
coal in tropical swamps. Oil and gas.
4.
(a)
Evaluate the relative importance of the geological factors that favour the
formation and accumulation of large scale oil and gas deposits.
(b)
evaluate the importance of anticlinal traps in the formation of large scale oil
and gas deposits.
Essential nature of :
Source Rock
-
for production of hydrocarbons
origin of hydrocarbons
from marine plankton
significance of temperature and depth of burial
idea of the oil window
argillaceous shales/clays
Reservoir rock -
for storing of hydrocarbons
high porosity and permeability, e.g., well sorted
sandstones
Cap rock
for stopping vertical migration of hydrocarbons
impermeable strata to stop oil from flowing upwards to
surface, e.g., clay/mudstone/ shale argillaceous rock type
-
27
Oil Traps
-
for large scale accumulation of hydrocarbons
anticline - just one of several types of trap
fault
unconformity
lithological
salt dome
Earliest discoveries  many anticlinal traps – most now depleted
Extraction of oil from oil shales and oil sands – future trend.
Credit diagrams and appropriate examples
5.
Evaluate the role of geophysical and geochemical techniques in the search for energy
and mineral deposits.
First step narrow down search to 'potential areas' using remote sensing and satellites infrared imaging/computer analysis plus study of already available geological
maps/surveys.
Geophysical methods - seismic - most important for locating oil and gas
- magnetic (often airborne) - dense metallic minerals magnetite
- gravity (often airborne) - salt domes + dense metallic
minerals
- resistivity – sulphides
Geochemical methods In context :
mainly metallic ores
soil sampling solids and gases
vegetation surveys
stream sediment surveys
stream water analysis
laboratory investigations
- Borehole drilling most informative / slow / expensive / to
assess 3 dimensional shape and size of ore-body
- Assessment of grade and tonnage of ore body – rock
geochemistry
- Assessment of results – decision to mine or not
Credit descriptions and examples of the above methods. Breadth v depth
Credit annotated diagrams
28
GL5 THEMATIC UNIT 3 – GEOLOGICAL EVOLUTION OF BRITAIN
Section A
1.
(a)
(b)
(i)
WNW-ESE (accept E-W) (1)
(ii)
NNE-SSW (accept N-S) (1)
(i)
Angular (1) / chevron (1) / zig-zag (1) / pointed (1)
0-15° (1)
40-55° (1)
(ii)
1 : overfold / recumbent / smaller interlimb angle / scale (wavelength
and amplitude)
3 : hinge rounded / axial plane vertical / larger interlimb angle /
scale (1)
(c)
10  6.5 = 3.5 m
3.5/10  100 = 35%
(d)
Evaluation - HOLISTIC
From Tables :
decrease in intensity from S to N as shown by folding style (1) and
cleavage (1) and degree of crustal shortening (1)
From Fig 1a :
granites / thrusts / ophiolites / low-grade regional metamorphism
explained
Evidence conclusive ? suduction ? obduction ?
Variscan orogeny - pre-Variscan rocks affected
2.
(a)
(b)
(i)
cross bedding (or flute marks)
(ii)
lose energy / velocity (1) large grains first (1) finest longer to settle(1)
(i)
shale fine grained low energy (1) far from land (1) graptolites fragile
planktonic forms best preserved in low energy water (1) chert ooze
deposit (1) black rich in carbon (1) deep sea (1) anaerobic (1)
HOLISTIC - 3 valid points
(ii)
(c)
erupted under water (1 reserve) oceanic crust / ocean floor / basaltic
ridge volcanics (1)
thickest turbidites adjacent (2) = trench position (1) deep ocean / ocean floor /
spreading ridge to south east (1)
29
Section B
3.
(a)
Interpret the geology of the Tertiary Igneous Province of north west Britain in
plate tectonic terms
(b)
Describe the evidence for rifting and subsidence in the North Sea and evaluate
its relationship to plate movements in the Mesozoic and Ttertiary.
(a)
Related to tension / rifting and ocean floor production:
Late Cretaceous early Tertiary igneous activity to NW
Basaltic dyke swarms and lavas
Varied associated plutonic activity
Mantle plumes develop under NW Britain / Greenland
Opening of N.Atlantic
(Later) Granites due to melting of continental crust.
(b)
4.
Tensional regime
Rifting and subsidence
N-S orientated (Jurassic early Cretaceous - ends late Cretaceous) grabens
Palaeomagnetic evidence suggests that during the late palaeozoic (Devonian,
Carboniferous and Permian), drifted across the equator.
(a)
Describe the evidence from sedimentary rocks and fossils which suggests an
equatorial climate in Britain in the Late Palaeozoic.
(b)
Describe and evaluate the palaeomagnetic evidence.
(b)
Devonian
-
south of Equator / arid / red beds / alluvial / fluvial /
lacustrine / lack of fossils
Carboniferous
-
Equatorial / limestones / associated fossils / coal / tropical
swamps / forests / associated fossils
Permian
-
north of Equator / breccias / sandstones / dune-bedding /
haematite cement / evaporites / mudcracks / desert /
hypersaline / lack of fossils
Formation of remanent magnetism (Curie Point)
Angle of inclination - zero at Equator re late Palaeozoic
Latitude not longitude
Polar wandering curves
Inaccuracies due to absolute ages
30
5.
(a)
Describe a range of techniques for collecting geological data in the field and
explain how the data can be presented in a variety of forms.
(b)
Evaluate the usefulness of these techniques in the interpretation of the geology
of an area with which you are familiar.
(a)
Sediments :
(b)
Hand specimen descriptions / logs / sedimentary structures /
histograms / fossils / field sketches
Igneous:
Hand specimen descriptions / contacts / associated
metamorphism / textures re cooling history / field sketches
Metamorphic:
Hand specimen descriptions / foliations / field sketches
Structure:
Dip and strike / rose diagrams / field sketches
Maps / sections / geological column
Case study.
Reliability / accuracy of data / weathering - erosion effects
Inferred boundaries / outcrop availability
31
GL5 THEMATIC UNIT 4 – LITHOSPHERE
Section A
1.
(a)
(b)
(c)
2.
(a)
(i)
parallel (1) / irregular (1) / NE-SW (1) / variable widths of stripes (1)
/symmetrical(1) aligned (1) linear (1) alternating N and R (1)
(ii)
MUST BE PARALLEL TO STRIPES FOR ANY MARK
line through "central stripe" (2 marks)
line within limits of 200 m contour (1)
(iii)
must be normal (1) / parallel to stripes (1) / within ridge 200 m
contour (1) / symmetrical(1)
(i)
Bruhnes
(ii)
8
(iii)
longer reversed than normal
(i)
210  105 (1) / 2.6  106 (1) = 8.08 (1)
(ii)
different rates of production of oceanic crust / lithosphere (1)
varying forces (1) / ridge push (1) / slab pull (1)
varying rates of movement of convection currents (1)
plates of different sizes/masses (1)
different types of plate boundaries on either sides (1)
(i)
max horizontal (1) / min vertical (1)
(ii)
NE-SW / in-out of paper / at right angles to the other (1)
(iii)
thrust / reverse (1)
(b)
graded bedding (1) / right way up (1)
cross-bedding (1) / upside down (1)
conflicting evidence (1)
(c)
HOLISTIC - both compressional thus probably same stresses / probably same
time (but fold not faulted)
32
Section B
3.
Describe how the use of seismic studies may contribute to an understanding of the
theory of plate tectonics.
Discuss the importance of the different depths of earthquake foci to the theory.
Describe
Importance
Distribution of earthquakes related to
plate boundaries.
Plate boundaries
Circum Pacific / Alpine - Himalayan /
oceanic ridges = boundaries
Plate boundaries
Shallow foci at CPM
Shallow re rising hot material / mantle /
CPM / spreading / MOR and East
African Rifting
Benioff Zone at DPM
Subduction related to convection
Conservative (mainly)shallow / complex
San Andreas / complex / tear movement
(tomography including mantle ?)
(magma / plumes)
Labelled diagrams (almost certainly) essential.
Must address "importance" for higher marks.
4.
(a)
Describe the J. Tuzo Wilson Cycle.
(b)
Discuss how the present-day distribution of rift valleys might support the
theory.
Labelled diagrams (almost certainly) essential.
(a)
Description of phases (number irrelevant).
Rising mantle / tension / thinning / CPM
Rifting / African Rifts / CPM / rifting of continental lithosphere
Spreading ocean floor
Subduction / DPM / closing ocean
Collision
(b)
African rifting and mid-oceanic rifts re theory. Connection of both (Afar).
Rifting "irrelevant" to collision / DPM = "third part of theory".
(Midland Valley of Scotland, etc., in context)
33
5.
Describe how sedimentary basins may be formed.
Evaluate the importance of isostasy in the formation of sedimentary basins.
Note: (re specification) only expect one example (compressional or tensional).
Labelled diagrams (almost certainly) essential. Case study.
Compressional :
DPM / formation of lithosphere / orogenic belts / erosion
provides sediment (on either side ?)
Faulting / thrusting / folding contribute towards basin
formation.
Tensional :
Rifting. (North Sea basin ?)
Sediment from sides of rift. Infilling. Fault reactivation.
Isostasy :
weight of sediment leads to subsidence ± fault reactivation.
Isostatic rebound re orogenesis leads to increased sediment
production and erosion of basins.
34
MARK BAND CRITERIA FOR A2 ESSAYS.
Summary
Description
Outstanding
Marks out of
25
25-23
Very good
22-20
Good
19-17
Quite good
16-14
Modest
13-11
Minimal
10-8
Weak
7-5
Very weak
4-1
Unacceptable
0
Criteria
Not the perfect answer, but a candidate could not
be expected to produce better work at this level in
the time allowed.
Arguments are purposeful, well supported & show
both balance and style. Irrefutable evidence of a
thorough grasp of concepts & principles. A hint
of flair apparent in the work.
The answer is direct & explicit; shows the ability
to use knowledge & understanding & to discuss.
May be limited in terms of supporting material &
breadth of coverage.
Shows a reasonably secure grasp of the basics, but
answer may show some slight deficiencies in
terms of either knowledge & understanding or
directness & organisation.
Material is mainly relevant & sound, but points
need more development(& support). Could be
much more direct & explicit in approach.
Work impoverished by limited knowledge &
understanding; tendency to rehash prepared
material & to answer by inference. Answer rather
hit & miss.
Little evidence of knowledge or understanding;
unable or unwilling to address the question;
essentially random in approach.
Largely irrelevant; too brief; abundant erroneous
material.
Wholly irrelevant or nothing written.
Incorporated into this mark scheme is the assessment of candidates on their ability to organise
& present information, ideas, descriptions & argument clearly & logically, taking into
account their use of spelling, punctuation & grammar.
GCE Geology MS (Summer 2007)/JD
35
Welsh Joint Education Committee
245 Western Avenue
Cardiff. CF5 2YX
Tel. No. 029 2026 5000
Fax. 029 2057 5994
E-mail: [email protected]
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