GCE MARKING SCHEME
GEOLOGY
AS/Advanced
SUMMER 2011
INTRODUCTION
The marking schemes which follow were those used by WJEC for the Summer 2011
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.
WJEC regrets that it cannot enter into any discussion or correspondence about these
marking schemes.
PAGE
Geology - GL1
1
Geology - GL3
5
Geology - GL4
10
Geology - GL5
17
GL1
Q.1
(a)
(i)
to show dextral movement (1)
i.e. to SE on NE side, and to NW on SW side
[1]
(ii)
A Divergent
[2]
3 correct = 2 marks
1 or 2 correct = 1 mark
B Convergent
C Conservative
(b)
(c)
(d)
(i)
plate movement in opposite directions/past each other (1)
stress build up (1)
friction (1)
stress release (1)
[3]
(ii)
deeper from X to Y (1)
plate subducts to Y (East) (1)
point where 2 plates meet therefore
deeper toY (or equivalent) (1)
[3]
(i)
A (1)
[1]
(ii)
Partial Melting (1)
of upper mantle/peridotite/ultramafic rock (1)
[2]
increase in width (1)
reference to spreading ridge/divergent plate boundary/
sea floor spreading (1)
addition of lithosphere at spreading centre (1)
[3]
Credit other sensible ideas
(e)
Decrease in size of Juan de Fuca plate (1)
Rate of subduction greater than rate of spreading
of plate (1)
[2]
Total 17 marks
1
Q.2
(a)
(i)
All bars drawn correctly (2)
or
Error with 1 or 2 bars (1)
or
Error with more than 2 bars (0)
[2]
(ii)
Interlocking crystals R (1)
Correct size of groundmass / phenocrysts (1)
Euhedral shape of phenocrysts (1)
[3]
(iii)
2 stage cooling (1)
Phenocrysts slow cooling (1)
Groundmass faster cooling (1)
max 2 of these
[3]
Phenocrysts formed first (1)
(or groundmass second)
Phenocrysts formed at greater depth (1)
(or groundmass shallower depth)
(b)
(c)
(i)
Biotite mica (1)
[1]
(ii)
Plagioclase Feldspar/muscovite mica/hornblende (1)
[1]
(iii)
Granite (1)
Coarse-grained (1)
Silicic/quartz/orthoclase/lacks mafic minerals (1)
[3]
F is country rock or equiv (1)
Hornfels/metamorphic rock (1)
Baked margin/in metamorphic aureole (1)
Contact metamorphism (1)
max 2 of these
[2]
or
F is igneous (intrusion/lava) (1)
Cross cutting/overlying (1)
Dolerite/Basalt (1)
Two separate igneous events (1)
max 2 of these
Credit other sensible ideas up to 2 marks each
e.g. xenolith and explanation
magmatic segregation
impact of faulting
Total 15 marks
2
Q.3
(a)
clastic/granular/fragmental (1)
sub-rounded/rounded (1)
0.3-1.5 mm (1)
medium grain size (1)
reasonably well sorted (1)
[3]
(b)
Quartz harder/feldspar softer (1)
Quartz no cleavage/ feldspar has cleavage (1)
Quartz resists erosion better or equivalent (1)
Quartz resistant to chemical breakdown (1)
Feldspar undergoes chemical breakdown/hydrolysis/ to clay
minerals (1)
[3]
max 3 of these
(c)
Sandstone G = orthoquartzite (1)
[2]
Sandstone H = arkose (1)
(d)
(i)
umbo/unbone/hinge line (1)
[1]
(ii)
bivalve (1)
[1]
(iii)
ripple marks (1)
[1]
(e)
[4]
Description of environment
(Maximum 2 marks)
Water/marine or sea /river or fluvial/lake/beach
or shoreline
Shallow
Current
High Energy
Reasons
Bivalves
Fragmented/death assemblage
Ripples
Absence of feldspar/ mostly quartz
Rounded grains
Moderately well sorted
To gain the reason mark there must be an appropriate link to the
description
Total 15 marks
3
Q.4
(a)
Time taken for half of parent isotope to decay to daughter (1)
Or equivalent.
(b)
[1]
[2]
number of halflives elapsed
0
1
2
% parent
isotope
100
• 50
• 25
% daughter
isotope
0
50
• 75
(1) per correct row
(c)
4 half-lives (1)
[2]
Credit any relevant working (1)
(d)
(i)
Dyke (1)
[3]
Discordant (1)
Sheet-like/long and thin/linear (1)
(ii)
Any reference to heat/metamorphism from intrusion K (1)
[1]
(iii)
Drawn so L cuts off dyke J on map R (1)
[4]
Conglomerate younger than dyke J (1)
Conglomerate younger than K because contains fragments of
K (1)
Dyke J older than K because K affects dyke (1)
Total 13 marks
4
GL3
Q.1
(a)
(b)
(i)
670m (accept 600 – 800)
[1]
(ii)
Damage to nuclear reactors – highly dangerous (radioactive leak)
[1]
(i)
Normal (1R)
Hanging wall(1)= downthrown (1) (footwall = upthrow)
W = Youngest rock on the downthrow side (1) & Fault dip is to W (1)
(Max 3 marks)
[3]
(ii)
After - Pliocene (5-4 Ma) (1)
Before - 125,000 yrs (1)
Younger raised beach (unconformity) not displaced (1)
(Max 3 marks)
[3]
(c)
Unlikely (1) as the fault has not moved for 125,000 years/older than 35,000
(1R)
However, no guarantee that it won't move again (1)
(Max 2 marks)
[2]
(d)
Holistic - Landslips, marine erosion, rising sea level, tsunamis etc.
Two or more discussed.
(Max 3 marks)
[3]
Total 13 marks
5
Q.2
(a)
(b)
Orientation - dip towards the cutting (day-lighting into open space) (R)
Rock type
Sandstone (permeable and competent/strong) (1)
Shale (impermeable – weak) (1)
Structure
Sandstone jointed (1)
Cracks developing (1)
Groundwater
(3 marks - R plus any 2 explained)
ABC-
[3]
Changes in height/position (1)
Rate of change increase (1)
Microseismic events as rock begins to slide (1)
Increase in number/size/rate (1)
Changes in the width of surface cracks (1)
Increase in size/rate (1)
[2]
PQR-
Laser beam measures distance between fixed points (1)
Changes in the distances – decrease (1)
Tiltmeter records changes in inclination of wall/face (1)
Change in the rate – increases (1)
Measure tilt/inclination of borehole (1)
Greater distortion from vertical with strain changes (1)
Holistic (Max 4 marks)
(c)
(d)
[2]
X-
Rock Step
Reduces slope height (load)
Allows for a steeper slope angle of face (1)
Reduces height for blocks to fall/catch falling blocks (1)
YRetaining Wall
Loads/supports toe of a potential slide/strength (1)
Prevents blocks falling on road (1)
Anchorage for rock bolts (1)
ZRock bolts
tie loose fractured strata (1)
to more stable strata (1)
on steeper slopes (1)
(Max 2 marks)
[2]
Increase the groundwater (pore) pressure (1)
Reduce friction (1)
Increase the driving force (1)
Lubricate the impermeable shale/slip plane (1)
(Max 3 marks)
[3]
Total 12 marks
6
Q.3
(a)
Describe the geological factors which control the pathways that landfill
pollutants (leachate and gas) will take in the event of their leakage from a
landfill site.
Rate of movement and direction of a pollution plume from a landfill site
depends upon Permeability &/or Porosity, structure (dip of bedding and
joints/faults)
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
STRUCTURE
Interconnected joints, faults, fractures, solution cavities. Dip direction.
Examples – limestone, sandstone, fractured/jointed igneous and met
rock
Case studies given credit
[15]
(b)
Explain the measures needed to change an abandoned sandstone quarry into
a landfill site and to reduce the dangers from decomposing domestic waste.
Site must be capable of retaining waste - sandstone permeable
(fractures/joints/porous)
Permanent containment – clay lining by compaction of clay,
plastic/geomembrane
Careful monitoring of hydrological system – wells outside landfill
Venting of methane gas – boreholes within the landfill
Leachate management system – porous pipes for removal/recycling of
leachate
Holistic approach (max 10 marks)
[10]
Total 25 marks
7
Q.4
(a)
Describe
(i)
(ii)
two potential benefits
two potential hazards
of living in an active volcanic region, dominated by frequent basaltic
eruptions.
(i)
Good soils
Geothermal power
Tourism
Other (e.g. mineral water -Volvic)
Any two stated (2 marks)
Described and developed and/or using examples (3 marks)
(Max 5 marks)
(ii)
Holistic
Hazards associated with type of magma – mafic. Expect lava flows,
ash, gases, lahars
Basaltic magma (less silica – less viscous) – divergent plate
Non-viscous - Fluid - fast moving (initially few km/hr,
cooler at front of flow thus more viscous)
- less warning but rarely kill (except - Nyirongongo,
Zaire in 1971)
- flows further - more hazard to property on lower
slopes
- hotter initially
Hazards associated with ash and gases relating to agricultural land,
roads, bridges and buildings. Also accept earthquake, tsunamis.
(Not pyroclastic flows, blast/explosion or max 7)
Examples (Etna, Nyiragongo, Iceland, Hawaii etc.)
(Max10 marks)
[15]
(b)
Using case studies, discuss the effectiveness of some of the measures used
to minimise loss of life and damage to property in volcanically active areas.
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/case study – Max. 7)
[10]
Total 25 marks
8
Q.5
(a)
(b)
Describe how ground subsidence may be related to the extraction of
(i)
(ii)
rock and minerals
water
(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]
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]
(Max 10 - 7 if only mention one)
Total 25 marks
9
GL4
Q.1
(a)
Description (Max 2 marks)
Use of numbers (size and height)
Largest size 200 m (near the top of the sill)
Smallest at base/top (chilled margins).
Account (Max 2 marks)
Cooling rate v crystal size
Effect of gravity settling and room for crystal growth further down
(Max 3 marks)
(b)
[3]
(i)
Height above
base of sill (m)
Augite
(pyroxene)
Plagioclase
Feldspar
Dominant
Plagioclase
composition
Top (300)
50
48
Ca-rich
200
30
67
Na-rich
150
32
65
Na-rich
50
Base (zero)
46
(45 - 48)
50
(63 - 67)
52
Ca-rich
48
Ca-rich
[3]
(ii)
Ca forms first (1)
higher temperature (1)
later crystallisation is more Na-rich – at lower temperatures (1)
fractional crystallisation – Ca removed from melt to make it more Na-rich (R)
(Max 3 marks)
[3]
(c)
(i)
(ii)
(d)
Associated with maximum decrease in Plag/Pyrox curve
(Credit on Figure 1a if necessary at approx. 16m/4mm)
(Max 1 mark)
[1]
Cross at top ~300m (or base ~zero m) within 2mm (R)
(on Fig. 1b if necessary)
Chilled margins (1)
Faster cooling (1)
Less time to differentiate/fractionate (1)
(Max 3 marks)
[3]
Granite contains silicic minerals e.g. quartz/muscovite
Lower in Bowen's reaction series
More in equilibrium than mafic minerals
(Dolerite vice versa/a plug/aug/oliv)
(Max 2 marks)
[2]
Total 15 marks
10
Q.2
(a)
(b)
(c)
(d)
X = Sedimentary (1)
Y = Igneous (1)
(Max 2 marks)
[2]
Temp/Depth (1) 10°C km-1 (1)
(Max 2 marks)
[2]
(ii)
Line at 25°C km-1
[1]
(iii)
B (1) (mark C correct if erroneously drawn higher than B)
Hornfels – Contact met (1)
High temperature/Low pressure (1)
(Max 3 marks)
[3]
(i)
Garnet porphyroblast correctly labelled
[1]
(ii)
Large crystals (1)
e.g. garnet (1)
Finer groundmass (1)
Mica (foliations) wrapped around garnet (1)
(Max 3 marks)
[3]
(i)
Horizontal line (left-right) (1)
[1]
(ii)
Holistic
Schistosity different orientation to inclusions in garnet
Indicates σ max has changed over time
S-shaped nature of inclusions (suggesting continuing change)
Accept porphyroblasts may have rotated
(Max 2 marks)
[2]
(i)
Total 15 marks
11
Q.3
(a)
Possible options
(Max 8 marks)
[8]
(b)
Reversed fault
[1]
(c)
Slickensides (1)
Recrystallisation of minerals/scratches along fault in the direction of
movement (1)
[2]
(d)
1. Dyke
After Trias
Tension – NE/SW
2. Fault at A
Downthrown to SW
Strike-slip
Last movement
sinistral strike-slip
(Max 5 marks)
Yes – cuts Trias(1)
Credit Jurassic is younger than Trias
Yes BUT NW – SE (as Dyke is
orientated NE/SW) (1)
Yes – Youngest rock (Trias) to SW (1)
Yes – vertical dyke offset (1)
Credit could have been formed by
oblique fault (slickensides not
completely vertical) or ref to
reactivation (strike-slip and vertical
movement)
Not according to the slickensides
which show LAST movement was
near vertical (1)
[5]
Total 16 marks
12
Q.4
(a)
Cycle
A
B
C
Cycle length (years)
• ~100,000 (1)
Possible cause
of Milankovitch cycle
Eccentricity (variations in the
shape of Earth's orbit)
• Obliquity (variation
in tilt of Earth's
axis) (1)
~41,000
• ~23,000 (1)
Precession (variation in the
wobble of Earth's axis)
[3]
(b)
(i)
(ii)
(c)
(d)
1.
2.
G = appropriate trough (15,000/135,000) (1)
I = appropriate crest (Present/120,000) (1)
(max 2 marks)
[2]
18
O is heavier than 16O
More 16O is evaporated from the sea
Returns via water cycle in interglacial – current 18O/16O ratio
16
O locked in ice during glacial – ocean richer in 18O
18
O/16O ratio is incorporated into the carbonate shells of forams
(Holistic - max 3 marks)
[3]
Volcanism, respiration of biosphere, weathering of limestone (1)
Chemical weathering of silicate rock (photosynthesis) (1)
(max 2 marks) (accept photosynthesism)
[2]
(i)
Direct correlation between CO2 and temperature variation
Positive correlation – Increase in CO2 reflects temp increase/decrease
in ice. Numbers credited
[2]
(ii)
Cause and effect not established
Is CO2 the cause of ice age or vice versa
Other contributory factors – ocean rifting, mountain building,
Other greenhouse gases
N.B. - geological time, not industrial revolution
[2]
Total 14 marks
13
Q.5
(a)
(b)
(i)
Hill Peat (1)
[1]
(ii)
Erosion, cut by rivers/streams (1)
do not accept 'weathering'
[1]
(i)
1cm = 90 m thus
13 mm (1) × 90 m = 117 m (accept 112 m -122 m) (1)
[2]
(ii)
8 cm (1) × 25,000 = 200,000 cm or 2000 m or 2 km (1)
(accept 1975 m - 2025 m)
(iii)
Effect of topography (shallow to east)(1)
Beds get thinner to west (1)
Effect of dip (1)
(max 2 marks)
[2]
Dip of beds to south (1)
in a valley (1)
[2]
(iv)
[2]
Total 10 marks
14
Q.6
(a)
(i)
[2]
Sand percentage
• 80
Silt percentage
• 10
Clay percentage
(ii)
(iii)
10
Correct 0% sand base line - must be on this line
Between 90%-100% (1)
[1]
Pendleside Sandstone (1)
[1]
(b)
Bowland shale – Low energy (shale), marine (fossils)
Pendle Grit – Higher energy – associated with land (plants washed in)
Fast moving currents (turbidites?) – graded beds/flute casts
Rational answer with evidence (submarine river, river channel with lateral
grading from meandering channel etc.)
Holistic (Max 4 marks)
[4]
(c)
Bowland Shale - impermeable - Pendle Grit – permeable (1) clay
underneath sst
Water forced to the surface at interface between shale and overlying grits (1)
Accept the proximity of a small fault (1)
(Max 2 marks)
[2]
(d)
(i)
Trilobite (accept pygidium only, not tail) (1)
(ii)
MOL – poor (1) Only tail preserved. (1)
Could be benthonic, pelagic/planktonic - swimmer/burrower/walker (1)
(max 2 marks)
[1]
Environment - extinct group - no living relatives
to compare (uniformitarianism) (1)
only that it is marine (1)
Maybe a molt or broken frag. - energy not easy to tell (1)
Credit (may be a derived fossil)
(max 2 marks)
Max 3 marks
[3]
Total 14 marks
15
Q.7
(a)
(b)
(c)
Anticline/Antiform/Monochine (1)
Plunging SW (1)
[2]
Syncline to west (1)
Plunging SW (1)
[2]
Incorrect (1)
(1 km = half wavelength measured between APT shown)
Wavelength approx 2km (1)
Need 2 peaks or 2 troughs to measure distance (1)
(Max 2 marks)
[2]
Total 6 marks
Q.8
(a)
(b)
Holistic
Bowland Shale Group – shale
Overlain by Boulder Clay
Impermeable
Less leakage
Valley bottom – catchment
Stable, very little faulting in area
(max 3)
[3]
Holistic
• Rock type :
High. Permeable Pendle grit overlies impermeable Upper Bowland Shale.
(max 2)
• Dip (angle and direction) of beds
Low. Beds dip INTO the hill and too shallow (re stable angle).
(max 2)
• Steepness of the slope
High. Contours close together. Allows material to flow more easily down over
steepened slope.
(max 1)
• Local groundwater conditions
High. Evidence of spring and stream associated with each landslip. Shale
unstable when wet.
(max 2)
• Faulting
Low. Not in the case of more northern landslip (though credit southern slip as
showing a small fault near spring). Faults may not be mapped.
(max 2)
(Max 7 marks)
[7]
Max 10 marks
16
GL5
Unit 1 - Quaternary Geology
Q.1
(a)
(i)
Scarp and vale, valleys & ridges, cuesta (1)
[1]
(ii)
Limstones/conglomerates harder than shale (1) more resistant to
erosion (1) Dipping strata (1)
[2]
Boundary between permeable & impermeable beds (1)
water table (1)
[2]
lens shaped / other reasonable description of its shape (1)
dimension(s) e.g. width 20 m (1)
[2]
(ii)
Reef (1) contains colonial coral (1) massive (1) fossil diversity (1)
[3]
(iii)
Fossils e.g. corals accumulate on the sea floor / death (or life)
assemblage / calcite precipitated / by algae / or saturated warm seas /
between fossils / burial.
Holistic mark (3)
[3]
(iii)
(b)
(c)
(i)
Figure 1a - untrue - sea level fluctuates / alternation between limestone and
shale.
Figure 1b - true - reef is covered by lagoonal sediments / shale is deeper
water sediment.
Holistic mark. (4)
[3]
17
Q.2
Evaluate the statement:
"The Glacial and Interglacial deposits and landforms in Britain provide an incomplete
record of climatic fluctations and varying sedimentary environments for the
Quaternary"
[25]
Descriptions - up to 19 marks :
Glacial
Landforms related to glacial erosion. Cwm (corrie/cirque), arête, hanging valley,
glacial trough, roche moutonee etc.
related to glacial deposition. Moraines (terminal, recessional) drumlins, crag and tail.
Deposits
–
Till. Erratics
Interglacial
Limestone Pavements. Formation of Peat. Fossil content.
Evaluation - 20+ marks :
Landforms and deposits indicate that climate change must have occurred but they are
limited in the data they provide. May be fragmentary. Erosion / no deposition leaves
incomplete record. Very difficult to date.
Landforms and deposits do indicate changes to the sedimentary environments during
the Quaternary. Need other information such as fossils for reconstruction of the climate
Sediments from a marine deposit give a more continuous record.
18
Q.3
(a)
Describe the evidence for sea level change during the Quaternary.
(b)
"Sea level change in the Quaternary is linked to continental ice sheets."
Evaluate this statement.
[25]
Descriptions - up to 19 marks :
(a)
Raised beaches, inland sea clifs, river terraces etc.
Submerged features (rias/fjords, submerged forests.)
Oxygen isotopes.
Evaluation - 20+ marks :
(b)
Isostatic sea level change in response to mass of ice locally on the
continents, displacing the mantle. Isostatic change is localised phenomenon
that can be more directly related to local quantity of continental ice.
Eustatic sea level changes in response to changing volumes of continental ice.
Evidence can be derived from oxygen isotopes for a global quantity of continental
ice. Superimposition of the two changes (and their differing rates) create the
landforms and evidence seen today.
Melting sea ice causes no change in volume. Melting continental ice adds to volume
of water in oceans.
Tectonic activity (such as in Alaska) can cause sea level change unrelated to
continental ice sheets. Also climate warming causes thermal expansion.
19
Q.4.
(a)
Describe turbidity currents how they are caused.
(b)
Evaluate the use of the sediments and sedimentary structures in interpreting
the physical processes that lead to the formation of turbidites.
[25]
Descriptions - up to 19 marks :
(a)
High density fluid (mixture of sediment and water) flows beneath less-dense
fluid (clear seawater). Flows down continental slope under gravity at high
speed (~100 kmh-1).
Accumulation of sediment on continental shelf. Often offshore from major
river mouths. Sediment becomes unstable (earthquakes, volcanic eruptions,
mass movement, storms).
Evaluation - 20+ marks :
(b)
Graded bedding, repeated cycles of sedimentation, Bouma sequences, flat
laminations and cross bedding all give good data on the cyclic changes of
energy.
Flute casts, cross bedding and sole structures (prod/bounce/groove marks
and flute casts) can give good indication of flow direction. Convolute bedding
and load casts only give an indication of the post-depositional processes as
the sediments de-water.
20
GL5
Unit 2 - Geology of Natural Resources
Q.1
(a)
(i)
Systematic sample, regular intervals, spaced 1 km apart. Grid pattern,
linear transects at right angles to each other or similar descriptive
terms.
[2]
(ii)
As above - 2 ¯ 1 mark for 50ppm + 1 mark for 200ppm.
[3]
(iii)
Disadvantage – if area has been glaciated soil may not reflect
underlying geology. On slopes soil moves downhill resulting in a
dispersal of the geochemical anomaly.
[2]
21
(b)
(i)
1 mark for drawing a linear band/line left to right at 1500ppm values,
1 mark for locating line above 1500 values and below 30 and 50 values
1 mark for not cutting through stream to the west
- max 2
[2]
(ii)
Dispersion/dilution/ erosion and addition of other sediments, chemical
weathering/breakdown of minerals.
[2]
(iii)
Boreholes / test drilling will confirm.
Supporting evidence :
Vegetation survey - ashed remains of vegetation or using indicator
species to detect areas which might have high concentrations of
metals in the soil.
Streamwater survey to detect dissolved ions of metals in solution.
Samples taken then analysed using mass spectrometer to calculate
metal concentrations in ppm
Geophysical : Seismic, electrical, gravity surveys.
Holistic
[4]
Total 15 marks
22
Q.2.
Descriptions - up to 19 marks :
Importance of water – sources: magmatic, meteoric, groundwater, seawater.
Igneous – pegmatites, porphyry copper, hydrothermal, black smokers.
Sedimentary – Residual deposits. Placer deposits. Banded Ironstone Formations.
Evaporites.
Evaluation - 20+ marks :
Other factors important not just water: source of elements, tectonic setting,
geothermal gradient, rock type, rock structure, climate, relief, sea level etc.
Q.3
Descriptions - up to 19 marks :
Planktonic life in surface waters of oceans.
Source rock - clay/shale, organic content. Reservoir Rock - porosity/permability. Cap
rock-impermeable clay/shale. Depth / temperature and length of time buriedformation of kerogen. Oil window. Traps - anticline, fault, unconformity, salt domes.
Evaluation - 20+ marks :
Source rock, reservoir rock, cap rock and trap ALL essential for commercial
accumulation.
Q.4
Descriptions - up to 19 marks :
(a)
Explanation depends upon case study of raw material. 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 - 20+ marks :
(b)
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
maximum levels of pollution.
23
GL5
Unit 3 - Geological Evolution of Britain
Q.1
(a)
inclination gets steeper towards the poles
[1]
positive values in the northern hemisphere (needles point into the ground)
negative values in the southern hemisphere (needles point up in the air
[1]
(b)
(i)
60ºS
[1]
(ii)
-50º
[1]
(i)
ONE choice = fossil / limestone / erosional surface
Explanation to match choice
[1]
[2]
(ii)
ONE choice = black shales / graptolites / turbidites / volcanics
Explanation to match choice
[1]
[2]
(i)
correct position of line approx NE-SW
[1]
(ii)
palaeomagntism – Wales and Scotland/plates separated
fossils - separate provinces / benthos cannot cross ocean
sediments – deep oceanic between continental shelves
(c)
(d)
Holistic
[4]
Total 15 marks
Q.2
(a)
Describe the location and large-scale geology of the Variscan orogenic belt in
the British area. Evaluate the extent to which the geology of the Variscan
orogenic belt enables are construction of the plate tectonic setting in which it
developed.
(b)
Evaluate the extent to which the geology of the Variscan orogenic belt
enables a reconstruction of the plate tectonic setting in which it developed.
Descriptions - up to 19 marks :
Location - main effects in SW Britain. Ages - Devonian Carboniferous rocks.
Trend of structures mainly E-W but variable further north e.g. N-S Pennine anticline.
Tight vertical and overturned folding to SW. Lizard thrust. Obduction of ophiolites.
Deformation less intense further north. Preservation of coalfields in synclinal basins.
Low grade regional metamorphism slate grade in SW. Granitic batholiths and
associated mineralisation in Cornwall. Related vulcanicity elsewhere in Britain - Whin
sill.
Evaluation - 20+ marks :
Thrusting / ophiolites consistent with desctructive plate margin. N-S compression
producing E W trending structures. SW Britain nearer centre of collision zone with
more intense deformation/ metamorphism. Melting of continental crust or mantle
wedge followed by crystal fractionation and crustal assimilation to explain the
batholith.
Lizard ophiolites and not typical (age and chemistry.) Lack of andesitic volcanics.
Where have all the mountains gone ?
Total 25 marks
24
Q.3
(a)
With reference to examples from the British stratigraphic column, explain how
sedimentary rocks and their contained fossils may be used to interpret fluvial
and deltaic environments of deposition.
(b)
Evaluate the reliability of the evidence.
Descriptions - up to 19 marks :
Fluvial (Devonian//Carboniferous/Triassic.) Meandering river systems - fining
upwards cycles, river channel, floodplain, small scale cross bedded sandstones.
Flash flood conglomerates/breccias (alluvial fans/wadi. Fossil fresh water fish,
bivalves, plants. Haematite - oxidising conditions.
Deltaic (Coal measures/Millstone Grit.) Coal, seatearth, fossil soil, swamp. Deltaic
sediments – coarsening upwards cycles. Abundant plant material. Fossil
insects/amphibians.
Evaluation - 20+ marks :
Interpretation depends on uniformitarianism the reliability of which diminishes with
the age of sediments and fossils. Some sedimentary facies can be interpreted in
different ways. Cross-bedding, red beds, shales, and fossils all open to
interpretation. Could argue a delta is a number of rivers so not easy to distinguish
unless have large amount of spacial data.
Total 25 marks
Q.4
(a)
Describe the igneous rocks and structures of the Tertiary Igneous Province of
northwest Scotland and northern Ireland.
(b)
The igneous rocks and structures of the Tertiary Igneous Province have been
interpreted as being associated with the opening of the North Atlantic.
Evaluate this statement.
Descriptions - up to 19 marks :
Late Cretaceous /Tertiary abundant igneous activity in NW Britain.
Basaltic volcanic activity and associated gabbroic and granitic centres of igneous
activity
Flood basalts. Plutons. Dyke swarms. Sills. Columnar jointing. Locations.
Evaluation - 20+ marks
Mantle plume develops beneath north west UK and Greenland. Rifting and
development of spreading centre, opening of North Atlantic. Large volume of basalt
associated with mantle plumes. Hot spot trail to Iceland. Mid ocean ridge still active.
Evidence of tension (dykes etc)
Trend of dyke swarms a problem. Later granitic intrusions due to melting of
continental crust. Backed up by polar wandering curves.
Total 25 marks
25
GL5
Unit 4 - Geology of the Lithosphere
Q.1
(a)
(i)
σx = max (1) σy = min (1)
[2]
(ii)
A : folded / shortened
B : pulled apart (boudinage) / extended
compression v tension
[3]
(b)
(c)
Best of the 3 given as L shows elastic / plastic behaviour and then
failure consistent with A and B in Fig 1a.
Use of test not a good choice. Restricted application.
Are temperatures, pressures and time accurate ?
[3]
(i)
10 (1)
(Only one which) intersects the temperature range within the pressure
range. (All 3 coincide.)
( 2 valid points relating to T and P)
[3]
(ii)
actual intersection of GTG with T / where all 3 coincide (1)
therefore good (1) or: not good because of estimates (1)
[2]
subduction zone
low GTG / lower than stable crust / cold water / ocean floor
[2]
(iii)
Total 15 marks
Q.2
Descriptions - up to 19 marks :
(a)
Island arc subduction. Oceanic / oceanic collision. Trench. Subduction zone.
Relative density / age of oceanic plate.
(b)
Cordilleran. Oceanic / continental. Trench. Orogentic belt.
For either / both : increase in temperature with depth; water content lowers
M.Pt. etc
Evaluation - 20+ marks :
Theoretically: island arcs = basalts = just oceanic lithosphere.
cordillera = andesites = oceanic + continental lithosphere.
In practice : contamination / differentiation etc potentially "ALL" types at both
locations.
26
Q.3
Descriptions - up to 19 marks :
(a)
Layers 1, 2 and 3. Layer 1 sediments.
(b)
Sedimentary stratification / metamorphic foliation / igneous limited
(pyroclastics / lavas). Examples.
Larger scale layering / sedimentary cover of metamorphics, migmatites and
igneous base to continental crust. (Conrad discontinuity ?)
Sedimentary upper layer of variable thickness. Sedimentary basins.
Evaluation - 20+ marks :
Q.4
(a)
confined to Layer 1. Thicken away from MOR. Quantitatively insignificant.
(b)
primary stratification / secondary foliation (latter may obliterate former).
Descriptions - up to 19 marks :
(a)
Example(s).Older rock surrounded by or adjacent to younger rocks.
Africa and North America provide examples. Britain older to NW and younger
to the SE.
Evaluation - 20+ marks :
(b)
Continents "grow" due to obduction at DPM. Younger material is obducted
onto older material. Destructive plate margins. Essentially older material in
the centre / progressively younger outwards (e.g. North America). Obduction
may not be from all sides and continents may be split due to plate tectonics
(e.g. Britain.) Wilson Cycle.
27
MARK BAND CRITERIA FOR A2 ESSAYS
Summary
Description
Marks
out of 25
Criteria
Outstanding
25-23
Not the perfect answer, but a candidate could not be expected to
produce better work at this level in the time allowed.
Very good
22-20
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 work.
Good
19-17
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.
Quite good
16-14
Shows a reasonably secure grasp of the basics, but answer may
show some slight deficiencies in terms of either knowledge &
understanding or directness & organisation.
Modest
13-11
Material is mainly relevant & sound, but points need more
development (& support). Could be much more direct & explicit in
approach.
Minimal
10-8
Work impoverished by limited knowledge & understanding;
tendency to rehash prepared material & to answer by inference.
Answer rather hit & miss.
Weak
7-5
Little evidence of knowledge or understanding; unable or unwilling
to address the question; essentially random in approach.
Very weak
4-1
Largely irrelevant; too brief; abundant erroneous material.
Unacceptable
0
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.
28
QUICK GUIDE
K/U
Description
Discussion
Terminology
Outstanding
23-25
Not perfect BUT
Very good
20-22
Thorough grasp
Well supported.
Hint of flair + EVALUATION
Sound
Good
17-19
Direct/explicit
Limited support - breadth.
Lacks detail - depth
Significant
Quite Good
14-16
Basics
Slight deficiencies.
Limited scope relevance
Basic
Modest
11-13
Mainly relevant
Needs much more
development
Minimal
8-10
Limited/rehash
Hit and miss
Weak
5-7
Little evidence
Question not addressed
Very Weak
1-4
Irrelevant/erroneous
Too brief
Unacceptable
Thorough
Little
0
Thus key dividing lines are:
Outstanding
-
Across the board – no significant weaknesses
Very good
-
EVALUATION
Good
-
Good read - some omissions in content/detail/discussion
Quite Good
-
Essay title has been addressed but not a convincing argument
Modest
-
Bit difficult to follow. Do they really know?
Addressed the question but need much more discussion =
mark scheme
Minimal/Weak/Very Weak
-
Rehash at best - irrelevant material/no essay to mark/mark per
point ?
29
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