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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 2003
GEOLOGY
INTRODUCTION
The marking schemes which follow were those used by the WJEC for the 2003 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.
GEOLOGY
GL1
Marks
Q.1
(a)
A = Joint/Fracture
[1]
B = Bedding plane/Bed
[1]
(b)
Calcite.
[1]
(c)
Erosion.
Weathering.
Weathering.
Erosion.
4 correct = 2 marks, 3 correct = 1 mark
(d)
[2]
Freeze thaw
reference to moisture
expansion (on freezing),
causing opening up of joints/block separation/breaking off.
Also credit
related to temperatures at altitude fluctuating
above and below freezing,
[4]
Solution/carbonation
acidic, rainwater
solubility of/reacts with limestone
causing opening up of joints/block separation/breaking off.
[4]
or
(e)
(i)
Reduction in size.
Rounding.
[1]
[1]
(ii)
Abrasion or corrosion/attrition.
Collision between transported particle and bed/bank.
Collision between two transported particle.
"Knocks off corners".
[3]
14 marks
1
Q.2
(a)
1
2
Arrow parallel to horizontal line (pointing North).
Arrow dipping away from diagram at approximately
67 degrees from the horizontal.
[1]
[1]
(b)
Iron.
Moving/convection current/fluid/self exciting dynamo.
(c)
(i)
Iron/mafic/magnetic minerals.
Alignment.
Become fixed/solid/Curie temp.
Remnant magnetism.
(ii)
Shade of bar SB 180-65 Ma-part of 65 Ma.
[1]
(iii)
India was decreasing its latitude/
moving towards the equator/
moving Northwards.
[1]
(d)
[1]
[1]
Credit the following on diagram or text.
Strong.weak/positive.negative/above.below average magnetic readings
Normal and reverse magnetism
Magnetic poles reversal/flip
Take on alignment of magnetic field at time of eruption
MOR or constructive/divergent plate boundary
Stripe anomalies are parallel to MOR
Stripe anomalies are symmetrical about MOR
Rising magma/lava is erupted at MOR
Movement of ocean floor away from MOR/older away from MOR.
[5]
14 marks
(N.B. MOR = mid ocean ridge)
2
Q.3
(a)
E = Solar energy/the sun.
I = Radioactive decay/geothermal.
[1]
[1]
(b)
(i)
Crystalline/crystals.
Foliated/schistose.
Porphyroblastic.
Only credit "groundmass" if supported by
"medium grained" or "finer" or size measurements.
[2]
(ii)
Metamorphic.
Foliation/schistocity/alignment.
Presence of garnet.
[1]
[1]
(i)
Pre-existing rock (mantle, metamorphic, subducted).
Heat source.
Partial melting.
Minerals with lower melting points melt.
Minerals with higher melting points remain solid.
Melted portion forms the magma.
[3]
Plate tectonic activity/mountain building/uplift.
Erosion.
Xenolith in a lava/intrusive igneous body.
[1]
(c)
(ii)
(d)
Accept reference to
Folding, Faulting, Slickensiding, Dipping beds.
Credit:
Quality of diagram/fieldsketch.
Reference to Scale.
Detail of feature, e.g. "normal fault", "anticline".
Specific location of feature, e.g. field location.
Nature of stress involved, e.g. compression or tension.
Labelled or descriptive features of the structure.
Total 16 marks
3
Q.4
(a)
(i)
(ii)
Trilobite.
Trace fossil/track/trail/print/burrow/imprint.
[1]
[1]
(b)
(i)
Random orientation/no alignment.
(accept that they all lie flat on the bed).
[1]
(ii)
(c)
Weak current
because:
they would be aligned by a strong current
they are unmoved/still present
they are undamaged.
[1]
[1]
Annotations to include some of the following:
Original shell buried/trapped.
Soft parts already destroyed.
Lithification (of sediment to sedimentary rock)
shell dissolved/decomposed
by acidic fluids.
Minerals infill
Precipitated from fluids passing through the rock.
**Cast (reserved mark)
Cast is a replica of the original.
Original hard parts no longer exist.
** Mould (reserved mark).
External mould.
[6]
N.B.
Mould and cast are both reserved marks; they have to be present to achieve
full marks.
(d)
(i)
(ii)
Transported.
[1]
From life position/before burial/after death/before fossilised.
[1]
3 of the following
[3]
Death assemblage
broken
aligned
sorted
can be derived
out of life habitat
Life assemblage
unbroken
non-aligned
unsorted
never derived
in life habitat
16 marks
4
MARK SCHEME
GL2(a)
SUMMER 2003
SPECIMENS
A = QUARTZ
B = SPOTTED ROCK
C= BIVALVE (ONE VALVE OF A COCKLE SHELL)
5
Q
1
response
a
b
mark
(i)
cuts across folded/horizontal/tilted beds
1
1
(ii)
(porphyritic) crystalline texture
1
1
(i)
scrape mineral across an unglazed tile
1
white powder 1
scratch mineral with equipment specified
1
no scratch with any 1
(accept > 5.5 but not = 7)
look for regular breakage
c
2
1
quartz
1
(i)
patches of new mineral growth
1
rock recrystallised (waterproof)
loss of bedding, etc
1 mark
spotted rock/hornfels
1
3
(ii)
(contact) metamorphism (not regional)
1
1
(iii)
position on Map 2 (anywhere with B in SE corner 1
of map)
1
a
drawing shape
square (or rectangular
)
quality of detail
scale
labels pallial line/teeth and sockets/
hinge/muscle scars/ligament/
crenulated margin (not ribs or pallial
sinus)
1
2 max
1
2 max
6
bivalves are equivalve, inequilateral (including
plane of symmetry)
3 max
brachiopods
are
inequivalve,
equilateral
(including plane of symmetry)
3 max
4
(i)
Completion of beds 2 – 5 (treat labels as a guide
to the beds) 1 reserved mark for thicknesses shale
texture/irregular base bed 4/coarse bed 4/grading
beds 2 + 4 (any 3)
1
4
(ii)
15/20mm
1
1
Graptolite
But 2 stipes/pendant habit/Didymograptus
Therefore Ordovician (not Silurian)
(older than Silurian)
1
1
1
3
look for diagrams which suggest that
a
b
6
(ii)
b
3
1
only irregular fracture 1
6
c
(flutes) scour and fill
passage of turbidity current
d
4
a
1+1
1
2
2 max
2
3 correct for 2 marks
2 correct for 1 mark
3 in right place but wrongly labelled = 1
2 marks
2
inclined
folds are asymmetrical
1
1
2
east
1
younger beds on downthrow (hanging wall goes
down)
1
2
the azimuth/bearing measured from north
NW (315º) to SE (135º)
south west
1
1
1
3
thrust/reversed
1
1
horizontal base of C and labeled (uncon)
discordant edge of pluton
1+1
1
fault F1 (dip/arrows/label)
2 max
folding





4 max
graptolite
graded beds
shale
fossils replaced by pyrite
black colour
greywackes/turbidites
(i)
(ii)
b
c
(i)
(ii)
5
a
b
antiform and synform/labelled axes = 1
limbs to show asymmetry = 1
inclined axes 1 = 1
base of Unit B beneath synform = 1
either fold beneath uncon
superposition:
E dips beneath G therefore
apparently older
cross-cutting: dyke (rock unit A) younger than
other units/fault F3; x-cut: fault younger than
Units
include fragments: G contained in E therefore
older
(superposition:
cannot apply as beds are
overturned) other explanation for fossils in E =
7
1 max
10
1
1
1
1
1
4
GEOLOGY
GL3
Q.1
(a)

Ash fall
 Lahar (1)

(water from lake or
melted ice cap)
Pyroclastic flow (1) 
(nuees ardente)
Volcanic gas (1)
[3]
(b)
A-
Ash FallWeight of ash (1)
Ash from fine powder - bombs (1)
Rapid - can be up to 1 metre /hour (1)
Often mixed with water from torrential rain (1)
Causes roofs/walls to collapse (1)
Examples - Pinatubo, Vesuvius, Krakatoa (1)
Other sensible qualification (1)
B-
Lahar Rapid burial by forceful flow of mud/ash plus rock (1)
Rapid Speed - qualified (45km/hr) (1)
Hot (1)
Caused by lake overflowing/torrential rain/melting ice cap (1)
Little warning given to evacuate (1)
Sets like cement (1)
Examples - Nevado del Ruiz/Mount Ruapehu (NZ)/Pinatubo (1)
Other sensible qualification (1)
C-
Pyroclastic flow (Nuees ardentes)Rapid flow of hot gas/debris (1)
Rapid - 100km/hr (1)
Hot - 800degC (1)
Little warning (1)
Moves over water (1)
Examples : Pinatubo//St. Pierre/Monserrat etc (1)
Other sensible qualification (1)
D-
Volcanic gas Flow of volcanic gas causes suffocation (1)
Rapid (1) quiet (1)
Little or no warning (1)
Gases include Carbon dioxide, Carbon monoxide and chlorine.(1)
Gas disperses to leave no trace/no damage to buildings (1)
Example - Lake Nyos, Cameroon (1)
Other sensible qualification (1)
e.g. Overturn of volcanic lake, density of gases in hollows
(max 3 each)
8
[6]
(c)
Reference to particular hazard
Holistic - 3 valid points/examples.
e.g. Lava
Evacuation, hazard mapping,
diversion/blocks, dropping-spraying with water,
explosion of flow margin,
prediction devices.
e.g. Etna
[3]
Total 12 marks
Q.2
(a)
(i)
22 - 23hrs (1)
[1]
(ii)
9750/15 (1)
= 650 km/hr (1)
[2]
Too close to epicentre/no time for warning (1)
[1]
(iii)
(b)
(i)
Wavelength

wavelength decreases (1)
Amplitude

amplitude increases (1)
Velocity

slows (1)
[3]
(ii)
(c)
A-
B-
C-
Small amplitude (1)
Large wavelength (1)
Indistinguishable from other waves/swell (1)
Evacuation road/Access for relief work (1)
Barrier (1)
Above projected height of flood (1)
Associated with Chamel for flood water (1)
Barrier to inland flooding (1)
Above projected height of flood (1)
Absorb energy of wave (1)
Associated with Chamel for flood water (1)
Waves pass through piles/easily drains (1)
Offer least resistance to force of water (1)
Strength of Orientation (1)
Above protected wave height (1)
9
[2]
D-
Trees dissipate wave energy (1) as they are flexible (1)
Trees – barrier (1)
Slow/breaking waves (1)
No development to destroy (1)
Provide run-up for waves to dissipate energy (1)
(Max 2 each)
[4]
Total 13 marks
Q.3
(a)
Describe the geological hazards that may result when engineering activities
associated with a major construction project interfere with natural processes
in coastal areas.
[10]
Holistic approach.
Problems of interference with coastal systems - erosion/deposition
Engineering activities include coastal defences (groynes, rip rap, sea walls etc)
Hazards areas
Coastal deposition – longshore drift pattern changed in unprotected
Reduction in amount of sediment deposition available to
provide a beach to protect the coast.
Increased marine erosion in unprotected area.
Base of cliff undercut - loss of stability for toe of landslide etc increase in mass movement
Increase lubrication of coastal sediments by sea water - mass
movement
Reference to case studies credited.
[10]
(b)
Explain the geological factors that need to be considered when selecting a
suitable site for a dam and associated reservoir.
[15]
Size & shape of valley and catchment
Rock strength of dam site
Porosity and permeability of reservoir site
Structure
Stability of site
Examples
Holistic approach
Long, narrow, deep to reduce evaporation
Suitable rock types explained. Clay/shale v
limestone/sandstone/crystalline rock
Leaking, need for grouting. Suitable rock
types - shale/clay/crystalline rock
Fold/faults/cleavage
(related
to
stability/seepage) Favourable and
unfavourable features – sedimentation rate
Rock beneath, mass movement on sides.
Earthquake risk
Credited
[15]
Total 25 marks
10
Q.4
(a)
Describe the distribution of earthquake epicentres around the world.
Describe:
(b)
Definition of epicentre
Narrow zones (few hundred kms wide, thousands of kms long)
in oceans
Wider zones on continents (Himalayas - Asia)
Sometimes join/divide e.g. Indian ocean
Associated with belts of mountains, ocean ridges, volcanoes,
rift valleys, island arcs, trenches. (e.g. Himalayas/ Atlantic,
Circum-Pacific)
Associated with plate boundaries - crustal tension/compression
Divergent (constructive) - plates moving apart (MOR/rift
valley) Convergent (destructive)- plates coming together
(trenches, fold mts)
Conservative - plates sliding past (San Andreas)
Mid plate examples/volcanic origin.
(max 5)
[5]
(1) Groundwater levels and pressure – Water in pores migrates into cracks
prior to earthquake (dilation) water levels decrease. Water levels increase as
more water diffuses prior to earthquake. Pore pressure changes with water
diffusion. Earthquake following increase in well levels/pore pressure. Credit
actual examples
(max 7 plus 1)
(2) Tilting and ground elevation- expansion of ground (by opening of
microcracks formed by stress) prior to an earthquake. Recorded by changes in
angles of slope and elevation . Use of tiltmeters/laser beams to accurately
measure variation across faults. EDM (electronic distance measurements)
from known fixed points.
Credit actual examples
(max 7 plus 1)
(3) Seismic activity - Variation in the seismic rate. Increase in the background
rate of minor earthquakes prior to a major quake. Seismic gap. The
Measurement of the velocities of P and S waves passing through and area.
Reduction indicates influx of water into rock as micro-fractures open. On
returning to normal, pore pressure rises = quake. Rate of return to normal =
Prediction of timing imminent. Duration of anomaly = predicted magnitude of
quake. (max 7 plus 1)
[15]
(c)
Explain how the destructive effects of earthquakes might be partly managed by
controlled stress release along faults.
Release of "locked" areas of fault by injecting fluids along fault to produce
smaller controlled earthquakes or underground explosions.
Denver - waste fluids injected into deep wells in fractured rock triggered
minor earthquakes until pumping stopped. Water lubricates fault zone.
Colorado - pumping water from deep wells - reduced water pressure/decreased
earthquakes
Both considered as a possible method of releasing the strain in "locked" parts
of San Andreas fault. Very expensive and not proven to be safe or feasible yet. [5]
Total 25 marks
11
Q.5
(a)
Explain how the geological problems associated with domestic waste
disposal in landfill sites might be overcome by good site selection and
engineering practice.
Site selection
Site capable of retaining waste
Free from disturbance (tectonic or subsidence).
Topography and structure- Existing hole/quarry-stable slopes
Bedrock and surface geology -Impermeable rock base to site – clay with low
permeability rates for leachate containment.
Hydrological regime - Dry site - above water table is preferred- (pore pressure
Gradient and rate of groundwater flow. Proximity to groundwater extraction.
Engineering Practice
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.
Combination (max 15 marks) Max 10 only if only site OR engineering.
(b)
Describe the potential uses of former landfill sites after waste disposal ceases
and the problems associated with their development.
Uses - Parkland, recreation, open spaces, greenbelt, low level industrial
development. Domestic development limited - problems of methane gas
hazard- leakage through permeable rock. (e.g. Loscoe - Derbyshire)
Ground instability on completion - subsidence.
Other problems associated with maintaining containment - groundwater
pollution. Must be accessible over 25 years to maintain.
Credit examples.
Total 25 marks
12
[15]
GEOLOGY
GL4
Question 1
(i)
Temperature at base of the crust (Moho)
Actual temperature.
Temperature at which dry (non-hydrous)
granite would begin to melt.
Temperature at which wet (hydrous)
granite would begin to melt.
Temp 0C
720
(710 - 730)
1075
(1065 - 1085)
740
(630-650)
[3]
(ii)
(iii)
(b)
275/10 (accept 250 to 300/10) (1)
= 300 C/km (1)
[2]
Less/lower in mantle (1)
Gradient is steeper in crust (1)
Rate of temp change with depth decreases (1)
(max 1)
[1]
(i)
(ii)
(iii)
Geothermal gradient is not high enough/crust not hot enough (1)
Temperature at Moho/base of Crust is not hot enough (1)
to cross the melting point curve (1)
Water reduces melting point (1)
[2]
Area above melting point curve (1)
below geothermal gradient (1)
[2]
The rising magma falls below/crosses the melting point curve (1)
It will crystallise before reaching the surface (1)
Between 8 -12 km from surface (1)
(2 max)
[2]
(c) Gas content affects
- Viscosity (1)
- Buoyancy (1)
- Explosion (1)
- Density (controls buoyancy)
(1)
- Fluid pressure (forcible intrusion if fluid pressure exceeds
confining pressure)
(1)
(Max 3)
Total 15 marks
13
[3]
Question 2
(a)
(i)
(i)
500 0C (1)
3.70 k bar (3.60 – 3.80) (1)
[2]
Pathway A1 → A2
Type - contact or thermal metamorphism (1)
adjacent to igneous intrusions/metamorphic/aureole/
baked margins (1)
plutons, magma chambers, sills, dykes (1)
range/high temperature – low pressure
Pathway B1 → B2
Type - regional (or dynamothermal/burial) metamorphism (1)
subduction zones/fold mountain root/deep burial
orogenic (1)
associated with destructive plate margins/organic belt
(1)
high temperature – high pressure (1)
[1]
[2]
[1]
[2]
(b)
Rock in Figure 2b (formed at X on Fig 2a)
Texture
Rock name
Rock in Figure 2c (formed at Y on Fig 2a)
Porphyroblastic or
Texture
Foliated or gneissose
Hornfelsic (1) Non foliated
banding (1)
Hornfels or spotted rock (1) Rock name Gneiss (1)
[4]
(c)
(i)
clay (1)
[1]
(ii)
most chemically diverse of rocks (1)
composed of clay minerals (1)
clay is rich in Al, Si and O (1)
other rocks do not contain aluminium (1)
mica from clay minerals (1)
Accept reasons for not including others (max 1)
(max 2)
[2]
Total 15 marks
14
Question 3
(a)
(i)
(ii)
(iii)
(b)
(c)
[2]
Thorax are free, pygidium are fused (1)
Other sensible (e.g. shape, number etc)
[1]
Function
- Allows for movement - rolling up (1)
- Protection/support internal viscera (1)
[2]
Benthonic –crawler (credit swimmer/burrower if qualified) (reserve
1)
Evidence:
Eyes on dorsal surface – can only see above (1)
Eyes small – lives on muddy bottom (1)
Eyes - light enough to see (sometimes) (1)
Flattened with wide cephalon/pygidium - stop sinking into soft mud
(1)
Cephalon shape as a shovel for burrowing in mud (1)
Other sensible - must relate to evidence (1)
(i)
[3]
Correct plot
Length – 20-22mm/Width – 30-32mm
[1]
Distribution in clusters (reserve 1)
Positive correlation/width/length directly proportional (1)
Credit range giving values (2-22/5-32) (1)
[2]
B (1)
Reasons - any two from:
Clumping representing successive moults (1)
Range from small (infant) to large (adults) (1)
Shows steady growth (1)
or
A - Death Assemblage would give only one area of
clustering/ sorting (1)
C - Gradual evolution unlikely to be preserved on same
bedding plane/would show continuous development. (1)
(3 max)
[3]
Trilobites extinct or
Fossil bivalves and brachiopods have modern living forms (1 max) –
do not double credit
Allowing direct comparisons to be made from modern to ancient or
Uniformitarianism (Present is the key to the past) (1)
(max 1)
[2]
(ii)
(iii)
(d)
Feature X - Eye (1)
Feature Y - Glabella (1)
Total 16 marks
15
Question 4
(a)
(i)
Fold element
Amplitude (in metres)
Description
 6m
Wavelength (in metres)
 40 m
Hinge shape
 Angular
Axial plane attitude

UPRIGHT
Axis orientation

PLUNGING to NORTH
[3]
(ii)
Anticline "v'ing" in direction of plunge (1)
Syncline "v'ing" opposite direction to plunge (1)
[2]
(b)
(c)
Stresses at X = tension/extension (1 plus 1)
Stresses at Z = compression (1 plus 1)
(max 3)
[3]
(i)
Arrows on CORRECT side of fault showing movement (1)
[1]
(ii)
Tension/extension (1 plus 1)
W-E or σ max (1)
[2]
Describe Upthrow to the West/downthrow to East (1)
Reversed fault movement/ (1)
Reference to displacement of unconformity (1)
Account Fault reactivation (reserve 1)
Post unconformity (1)
Compression (1)
(Max 3 - 1+ 1 (reserve) + 1)
[3]
(iii)
Total 14 marks
16
SECTION B
Question 5
(a)
(i)
Quaternary/recent sediment cover (1)
[1]
(ii)
Till (1)
[1]
(iii)
3. Youngest

Alluvium
2.

Till
ROCK HEAD
1. Oldest
 Ing (Silt/Sandstone
Conglomerate)
[2]
(b)
(i)
(ii)
Describe:
Along valley floor (1)
Dimensions: 4500 - 5000m long by 250m (widest
point) (1)
Trend – NE to SW (1)
Explain:
Flood plain deposit/meandering river (1)
(Max 1 describe plus 1 explain)
[2]
Describe:
Follows contours (1)
Parallel to valley sides (1)
Explain:
Horizontal/near horizontal/very gentle dip (1)
(Max 1 describe plus 1 explain)
[2]
Total 8 marks
17
Question 6
(a)
(i)
(ii)
(iii)
B (1)
60o dip to the SW (1)
(or reasons why others are incorrect involving dip and bed
orientation)
(max 2)
[2]
Unconformity (reserve 1)
Limestone (Garsdale) (1)
Ing (silt/sand/cong) (1)
Dip of beds - 60o (1) and horizontal (1)
Accept many others - swallow hole, joints, bedding planes,
limestone pavement, resurgence, clints, grikes, irregular base
to unconformity (1 mark each)
(max 3)
[3]
Limestone permeable/jointed (1)
Allows water to move vertically (1)
Ing. Impermeable (1)
Forces groundwater/water table to surface (1)
(max 3)
[3]
Total 8 marks
18
Question 7
(a)
(i)
(ii)
[6]
NW - SE
Fault characteristics
RF Hollintree Fault
Direction
Angle (degrees)
SW
74
Dip direction and angle
(degrees)
Downthrow direction
Throw (in metres)
N.E

Orientation (direction)
of the principal stress 
component (σmax)

Fault type
(b)
[1]
South Craven Fault
Direction
Angle
(degrees)
 SW
82

SW.
325 m (300-350)
SW-NE (or either)
No data
Not required
Reversed/compressional/  normal
tensional
(i)
Graben/rift valley (1)
[1]
(ii)
Rocks are less resistant to south (1)
UCM are mudstones/ more prone to erosion (1)
GL DBL are limestones/less prone to erosion (1)
No credit for they have been downfaulted)
(max 2)
[2]
Total 10 marks
19
Question 8
(a)
(b)
(i)
Horizontal line at ~250 m (1)
[1]
(ii)
Overlying horizontal limestone (1)
Description of folding (1)
- NE - SW axial plane trend (1)
- overturned in places (1)
- isoclinal/vertical/steeply folded Ing.(1)
- anticlines/synclines (1)
Reference to faulting (1)
(max 3)
[3]
Dam site
Advantage
- Limestone and Ing. - strong suitable support for dam
Disadvantage - Limestone may be prone to collapse
- Carbonation, underground caverns, karst features
- Leakage through/under dam
- dam site wide - large dam needed
- boulder clay impermeable but questionable stability
- strongly folded rock may be prone to fracturing
Reservoir
Advantage
- elongated, deep glacial valley that narrows reduces
evaporation
- Ing. proven to be impermeable (spring line)
- Spring/river to provide water supply
- clean water supply through limestone
- Boulder clay - impermeable.
Disadvantage - leakage through limestone - permeable/pervious
- will not fill to capacity above unconformity
- need for grouting joints/fractures/faults
- river silting
- faulting (reactivation!) leakage along shatter zone
- mineral vein contains lead – pollution
(max 6 marks)
[6]
Total 10 marks
20
GEOLOGY
GL5
THEMATIC UNIT 1
QUATERNARY GEOLOGY
Q.1
(a)
(b)
Western terminal moraine identified (Reserved 1)
Till (lodgement) showing orientation stops at terminal moraine (1)
(No till west of) terminal/end moraine (1)
Fluvio-glacial deposits to west of terminal moraine (1)
Fluvio-glacial deposits show flow to the west. (1)
(Max 2)
(i)
(ii)
(c)
(d)
[2]
Fluvio-glacial/river (1)
Outwash from melting glacier/meltwater (1)
Cross bedding/produced/indicates river direction (1)
[2]
Ice deposition/recessional moraine (1)
Formed when glacier was static (1)
During deglaciation/ablation/warmer period (1)
(Max 2)
[2]
Laminated clay = low energy of lake (1)
Pebbles = drop stone from ice blocks adrift in the lake (1)
(Alternating layers =) seasonal fluctuation in melting/energy level (1)
Coarse - spring melt (1)
Fine winter freeze.(1)
More energy / less energy related to grain size (1)
(Max 4)
[4]
Radiocarbon / radiometric dating (1) of
organic material washed in (1)
from top and bottom of the sequence (1)
Counting annual varve layers (1)
(Max 2)
[2]
Total 12
21
Q.2
(a)
(i)
(ii)
(iii)
Current ripples (1)
No bedload movement/not enough energy / velocity (1)
Greater amplitude / thickness / depth (1)
Greater wavelength/distance between crests (1)
[1]
[1]
[2]
(b)
Internal structure (1 Reserved)
Current (wind accepted) flow direction (either direction to match sketch) (1)
Erosion of stoss slope (1)
Deposition on lee slope by eddies (1)
Evidence of advancing ripple crests relating to internal structure (1)
(Max 3)
[3]
(c)
Coarse-grain (lag deposit) on base
= Upper planar beds. (1)
= High velocity flow/energy conditions of deeper channel (thalweg) (1)
Medium-grained sand
= Cross bedded aqueous dunes (1)
= Moderate energy of point bar/ lower water velocity (1)
Fine-grained sand
= Cross laminated current ripples (1)
= lowest energy / velocity shallowest water at top of point bar (1)
Fining up sequence - as meander migrates and energy decreases. (1)
Cycle repeated with subsequent meander (1)
(Max 4)
[4]
(d)
Difference - symmetrical ripples formed by waves (1)
Reason - orbital movement of water rather than unidirectional (1)
[2]
Total 13
22
Q.3
Describe and explain how variations in the Earth's rotation and orbit (as proposed by
Milankovitch) and the distribution of continents and mountains in the Quaternary may
affect global climate.
Eccentricity of orbit - shape of the Earth's orbit changes over 100,000yrs from circular
to elliptical
Axial Tilt - angle varies between 24.5 and 21.5 deg every 41,000yrs
Procession of equinoxes - Earth wobbles on its axis. The time of the year at which
Earth is nearest to sun changes over 23,000yrs.
Effect of each is minor but they may combine to significantly alter distribution of
solar energy between hemispheres. Results in climatic fluctuations - warmer and
colder conditions (Interglacial/glacial).
Credit diagrams.
Distribution of continents and mountain ranges controls oceanic and atmospheric
circulation. Climatic belts influenced.
Continents at poles/surrounding poles - Ice Caps form (Antarctic/Arctic.)
Northern Hemisphere - continents surround the Arctic Ocean preventing warm
influence of major ocean circulation from Tropics.
Southern Hemisphere - Antarctica - land cold covers S Pole. (radiant energy from
sun at low angle / reflected)
Position of mountain ranges - restricts or encourages the movement of winds e.g.
Himalayas Rain shadow effects.
Total 25
23
Q.4
With reference to examples, describe and explain how geological structure and
lithology control river drainage patterns, underground river courses and groundwater
flow.
Structure -
joints, folds, faults, bedding planes, other boundaries (unconformities,
igneous contacts etc.) Dip of strata.
Lithology -
resistance of rock to weathering/erosion.
Examples - crystalline rock versus drift/sedimentary rock.
Degree of lithification/cementation.
Composition of rock (e.g. sandstone versus clay)
Related to above:
Drainage patterns
- Radial drainage (Lake District, volcanic peak
etc.)
- Trellised drainage (e.g. related to cuestas).
- Effect of dip/joints.
Underground river systems
- Limestone caverns and water courses.
- Dry valleys. Springs.
Groundwater flow - nature of rock
- porosity/permeability.
Credit examples and diagrams.
Holistic - depth v breadth.
Total 25
24
Q.5
(a)
Describe the principles of the radiocarbon (14C) dating technique.
14
N changed to 14C by cosmic rays.
Decays back to 14N at a constant rate. 5730 years (half life)
14
C in atmosphere is constant - replenished by cosmic rays.
14
C is absorbed by living organisms - thus proportion in living organisms is
constant with atmosphere.
Detailed consideration of method of age determination sufficient for high/full
marks:
On death the 14C decays but is no longer absorbed. Proportion of 14C
compared to non-radiogenic carbon decreases compared to atmosphere with
time.
Decay curve. Labelled/discussed.
Used to date death of organism in years B.P.
Unreliable over 50, 000 years - thus only recent organic material can be dated.
Other errors - carbon pollution of the atmosphere etc.
(b)
Discuss the extent to which fossil plant remains provide evidence for climatic
fluctuations in Britain during the Quaternary period.
Fluctuations relate to changes from glacial to interglacial periods.
Maximum marks only if discussion is made of the "extent."
Plant - Pollen diagrams in particular
Fluctuating climate causes changes in vegetation recorded in pollen samples
Relative abundance of pollen species indicates climate (interglacial
lake deposits)
Glacial/pre-temperate climate - birch dominates
As climate warms - oak, elm, alder and hazel become abundant
As climate cools the pattern is reversed with deciduous trees replaced by
evergreens (fir and pine) and finally birch.
Plant fossils mainly on land - poorer environment for preservation but often
washed into lakes/sea where preservation is better.
Pollen is small and grains are tough - better for preservation.
Pollen is very abundant and widespread.
Other plant remains - leaves/ stems/ roots - evidence of type and climatic
regimes based on Principle of Uniformitarianism.
25 marks
25
THEMATIC UNIT 2
Geology of Natural Resources
Section A
Q.1.
(a)
gravity (settling)/of dense /early-formed / high M. Pt. minerals /
non-turbulent (1)
e.g. Li / Be / Sn / W / U (1)
hot aqueous (circulating) solutions/volcanic association/black smokers (1)
Cu ( Mo / Au / Ag ) (1)
(b)
(i)
[4]
Description:
1 of : pockets where limestone well-jointed/weathered/eroded (1)
Explanation:
2 of: due to jointing and faulting (1)
increases porosity / permeability (1)
increases water activity / solution (1)
pockets restrict erosion of bauxite (1)
[3]
(ii)
Wet and dry seasons (1) / intense chemical weathering (1)
[2]
(iii)
3 of: chemical weathering of limestone (1) /removed in solution (1)/
insoluble residue (1) / hydrated aluminium oxides (1)
[3]
12 Marks
26
Q.2.
(a)
(i)
(ii)
(b)
(i)
(ii)
thicknesses / dips (1)
symbols (1)
[2]
fold (1)
unconformity (1)
[2]
Cap rock:
halite (1)
Reason(s):
permeable sandstone / reservoir rock /
beneath impermeable (halite / shale)
prevents upward migration of hydrocarbons (2)
Name:
[3]
unconformity (1)
Description : folded / antiformal / source and reservoir rocks
eroded / truncated against(erosional) surface/
(plane of) unconformity (2)
[3]
(c)
Small/abundant/preserve well/widedistribution/environment
al indicators
/easy to recover/age/stratigraphy/P-T indicator/use in
identifying source
rock. [3]
13 marks
27
28
Section B
Q.3
(a)
Describe briefly the method of extraction of one named geological raw
material.
(b)
Discuss how the extraction might impact on a nearby community and how the
impacts may be reduced or controlled.
Named
Method of extraction:
e.g.
Environmental problems :
removal of overburden
description of quarrying/mining methods
strategy
relate to shape of "deposit"
blasting ? removal/machinery
accept labelled diagrams
waste/ground pollution including visual/
noise/dust / drainage / wildlife etc.
conservation
buffer banks/tree barriers/timings of
blasts
drainage/treatment/reclamation etc.
Total 25
29
Q.4
Describe one geophysical and one geochemical technique use to prospect for mineral
resources. In each case name a mineral for which the technique might be suitable and
explain any limitations that the technique might have.
Geophysical:
Named resource
Techniques
-
Description
-
e.g.
e.g.
oil / gas
seismic
gravity
explosions/ land/ ship/ reflection/ record of 2way time/ graphical representation to identify
structures/ oil traps
-
magnetometer/ land/ plane/ ship/ graphical
representation of magnetic readings/ depends on
changes in magnetic properties or distribution of
rocks i.e. structures
-
gravimeter/ land/ plane/ ship/ changes in
gravity/ changes in density of the underlying
rocks/ reflects the structure(s) graphical
representation (including labelled diagrams)
Geochemical:
Named resource
-
Technique
-
Limitations :
e.g.
tin / copper / (name of mineral)
stream sampling / water / sediment / soil (auger)
/(vegetation)
laboratory investigation / chemical analysis
(atomic absorption) spectrometer
laboratory and site for mineral/sediment
identification
plotted on map to locate (approx?) location of
source / deposit
e.g.
e.g.
gravity requires sharp density contrast
stream sampling / laboratory back-up
Total 25
30
Q.5
Describe and explain how rock properties and geological structures influence the
accumulation and flow of ground water.
Properties:
Porosity
N.B. Need descriptions for full marks
=
Permeability =
Grain size
permeability
% age pore space
rate of flow of fluid through rock in m/s
=
smaller the grain size higher the porosity lower the
(unless perfect spheres! – accept lower permeability but same
porosity)
Grain shape
=
greater the sphericity greater the porosity and permeability
Sorting
=
greater the sorting higher the permeability / porosity (?)
Packing
=
tighter the packing lower the porosity and permeability
Compaction
=
greater the compaction lower the porosity and permeability
Cementation =
greater the cementation lower the porosity and permeability
Structure:
Structure of aquifers e.g. confined (as London Basin) (credit perched in correct
context i.e. structure)
Diagrams. Must be well-labelled or explained.
(Properties/structure
Macro / micro fracturing = greater the fracturing higher the porosity and permeability)
Accumulation/flow
Porosity
=
Permeability =
%age pore space = accumulation
rate of flow of fluid through rock in m/s = flow
Holistic: breadth versus depth.
Total 25
31
A2 THEMATIC UNIT 3
Geological Evolution of Britain
Section A
Q.1
(a)
Evidence :
Cross-cutting/truncation/overlie/overstep/overlap/strata
(ages) missing
e.g. between Skiddaw Slate and Mell Fell
Conglomerate
or between Ordovician/Devonian
or Ordovician/Carboniferous
or Devonian/Carboniferous) (Any 2)
Stratigraphic age :
as chosen (1).
[3]
(b)
(i)
(ii)
(iii)
Type of plate boundary: destructive/subductive (1 Reserved)
Reasons:
2 of:
volcanicity with qualification (e.g. andesitic/
pyroclastic etc) (1)
plutonic igneous activity with qualification
(e.g. granitic/silicic etc) (1)
folding (1) regional metamorphism/slate (1)
[3]
Trend:
NE/SW (1)
Reason:
strike of Ord strata / strike of axial planes /
NW – SE compression (1)
[2]
Caledonian (1)
[1]
(c)
Marked as a whole such that palaeoenvironment / evidence / explanation match.
Palaeoenvironment:
fluvial/deltaic/alluvial/(terrestrial) (1)
Evidence:
channels/rounding/sorting/fans/red/
cross-bedding to the east (1)
Explanation:
water transport / flash floods / red (oxidation) etc (2)
[4]
13 marks
32
Q.2
(a)
Description:
Name:
3 of:
angular (to sub-) (1)
non-interlocking (1)
(very) poorly sorted/unsorted / stated grain sizes (1)
fine-grained matrix / matrix supported (1)
sandstone/arkose/feldspathic sandstone (1)
[4]
(b)
Two of:
Fossil:
Rock-type:
Environment:
poor preservation/destroyed/washed away (1)
medium/coarse grains poor for preservation (1)
subaerial (accept "float away" or equivalent)
high energy/erosion (1)
[2]
(c)
(d)
Grain shape:
little transport / close to source (1)
high energy environment (1)
variety of possible environments/no water or wind? (1)
Mineralogy:
feldspar = little chemical weathering of feldspar/
lack of water?
(1)
little transport/close to source (1)
relevant (negative ?) comment with respect to quartz
(e.g. very poor environmental indicator) (1)
[5]
(to match answers to (c) ) e.g. terrestria/fluvio/deltaic
[1]
12 marks
33
Section B
Q.3
Discuss the extent to which the occurrence of greywackes and their sedimentary
structures, interbedded with black graptolitic shales, indicate that parts of Britain once
experienced deep-water marine conditions.
Greywackes
description:
texture/mineralogy
turbidites/bottom of
continental slope "any"
environment/ rapid deposition
Black
anaerobic/lack of
oxygen
deep
water/ocean floor could be
shallow(er) – just lack of oxygen
Graptolitic
pelagic/fragile/pyritisation
-
float into deeper waters/lack
scavengers/weathering/erosion
found in deposits of all depths
extinct - problematic
preservation/shale key feature
Shales
fine-grained / travel distance
/sorting
-
no current
any depth
Sedimentary grading
structures
description: fining upwards/rapid
deposition
from
turbidity
currents
(Any valid sedimentary structure with context e.g. current bedding; bottom structures
etc.)
Early Palaeozoic age for deep water as indicated by graptolites = zone fossils
Allow "negatives" e.g. lack of brachiopods, corals, trilobites, limestones etc, etc.
Total 25
34
Q.4.
Describe and explain the evidence that suggests the past existence of shallow, tropical
marine conditions in what is now Britain. Where possible outline any other possible
interpretations of the evidence.
Rocks:
Fossils :
Limestones:
Bioclastic:
formation of: shelly/coral/reef
(/crinoidal)
Oolitic:
Bahama Banks / warm seas rich in
calcium carbonate
Chalk:
deep-water oceanic/some shallow
fossils
Corals
warm, shallow, marine conditions
Brachiopods
warm, shallow, marine conditions / less reliable
(Crinoids etc)
All strong on Law of Uniformitarianism:
present-day reef conditions
tabulate/rugose extinct
deep-water corals ?
Accept evaporites in context.
Dolomites.
Total 25
35
Q.5
Describe and explain the palaeoclimatic and the palaeomagnetic evidence which
suggest that Britain was much closer to the equator in the Permo-Triassic than it is
today.
Red sandstones/breccias :
description/significance of textures/mineralogy (quartz/
haematite)
sedimentary structures – dune bedding etc
lack of fossils
running-water deposits/braided streams/wadi deposits
Red shales / evaporites :
description
sedimentary structures – desiccation etc.
fossils absent (/rare/exotic)
Pre and post Permo-Triassic evidence of low latitudes e.g. swamps of Carboniferous
and warm, clear marine seas of the Jurassic.
Palaeomagnetism:
iron-rich/haematite-rich beds
possible to get data from red sandstones but difficult
any reliable data would give low angle of magnetic
dip/inclination
discussion of origin of remanent magnetism in
sedimentary rock re depositional origin in water and
post-depositional (e.g. cementation)
Credit realisation of no igneous rocks on mainland Britain but:
Credit outline of remanent magnetism in e.g. basalts re Curie Pt etc.
Could use igneous rock in other regions of plate.
Total 25
36
THEMATIC UNIT 4
GEOLOGY of the LITHOSPHERE
Q.1
(a)
(b)
(c)
(i)
Arrow at appropriate location. (1)
[1]
(ii)
~90km (Accept 85 -95) (1)
[1]
(iii)
magnetic / iron minerals in magma (1)
orientation in direction of magnetic field (1)
locked when magma falls below Curie Temp / solidifies (1)
reversal in polarity from normal with time (Reserved 1)
(1 Reserved plus any 2)
[3]
(i)
Distance/Time in working (1)
~ 4.5 (accept 4.0 to 5.0 incl) cm/yr (1)
(ii)
Explanation of the radiometric dating of:
Mantle plume (hotspot) volcanic island chains (2)
Accept also
Ocean floor sediments / thickness and distance from ridge (2)
Basalt rock samples dated plus distance from ridge (2)
Thickness of lithosphere v distance from ridge (2)
(Max 2)
[2]
Pacific (1)
Ocean ridge is not central in Pacific/MAR is central in Atlantic (1)
Ocean basin biggest (wider) in Pacific (older)(1)
Pacific surrounded by trenches (few in Atlantic) (1)
Subduction well underway at edges/ minor in Atlantic (1)
Faster spreading rate in the Pacific (1)
(4 max)
[4]
Total 13
37
Q.2
(a)
(i)
Continental crust
Ocean crust
Upper mantle
Composition
ANDESITIC / Granitic
(silicic) / granodiorite
("any" non-basic /
ultrabasic)
Basaltic
(mafic)
Peridotite
(ultramafic)
Relative Density
2.7
3.0
(accept 2.9 or 3.0)
3.2
[2]
(ii)
(iii)
(b)
Mass = density x volume. (1)
Pressure related to mass above (1)
M and N have different densities (1)
and volumes above = same mass (1)
Or equivalent (max 2)
[2]
Moho will rise beneath M (1) and sink beneath N (1)
As lithosphere seeks to maintain isostatic equilibrium.(1)(max 2)
[2]
(i)
(ii)
4. Top

OCEAN SEDIMENT
3.

PILLOW LAVA
2.

SHEETED DYKES
1. Bottom

LAYERED PERIDOTITE
(4 correct = 2 marks, 2 correct = 1 mark)
[2]
Y is OLDER 1)
Ophiolite represents Ocean crust (1)
during subduction at convergent (destructive margin)(1)
Obducted/scraped into accretionary prism (1)
Younger deposits are thrust/faulted (1)
beneath older (underthrusting) (1)
Credit annotation of diagram. (1)
(Max 4 marks)
[4]
Total 12
38
Q.3
Describe and explain how a study of earthquake body waves provides evidence for
the variation in thickness and mechanical properties of the lithosphere and
asthenosphere.
Holistic approach
Define earthquake body waves.
Use of/explanation of formulae for P and S wave velocities.
Incompressibility and rigidity versus density for P-waves
Rigidity versus density for S-waves
Depth profile of P and S waves to show velocity variation.
Depth of the Low Velocity Zone with distance from spreading centre.
Thickening of the lithosphere with age and distance from ridge.
Diagrams credited
Definition of the difference between Lithosphere and Asthenosphere in terms of
mechanical properties.
Lithosphere = plate. Cold (<1300o C isotherm). Brittle thus fractures.
Asthenosphere = partially molten (5 %) - Ductile thus flows.
Total 25
39
Q.4
(a)
Describe the variation in surface heat flow across a spreading ocean basin and
active continental margin.
Ridge -
(High) Thermally varied. High range of heat flow (high to
low) temperatures. Above world average.
Abyssal plain -
(Lower) Thermally stable: low range of heat flow. Below
average heat flow. Heat loss greater further from the ridge.
May increase above average at a "hot spot" e.g. Hawaii etc.
Trench -
(Lowest) Coldest lithosphere. Lowest temperature range.
Example.
Continental margin – (May be) very high adjacent to trench. Moderately high
at passive margin. Example
Diagrams credited throughout.
(b)
Explain how surface heat flow relates to plate tectonic and mantle
processes within the lithosphere.
Ridge -
Associated with rising convection current in the mantle
at spreading centre. Constructive margin. Heat loss by
conduction/convection/radiation. Results from rising
magma, "black smoker". Examples credited
Abyssal plain -
Owing to heat loss by conduction and radiation of older
lithosphere as plate moves further from spreading
centre.
Hot spot - relates to "mantle plume".
Associated with "mantle dynamics" rather than "plate
tectonics".
Trench -
as ocean plate descends before subduction. Descending
currents. Oldest lithosphere - max time for heat loss.
Continental margin - Melting of subducting plate (and/or overlying
mantle/continental root). Rising andesitic magma.
Examples. Effect of water on melting temperatures.
Diagrams credited throughout.
Holistic approach if there is overlap between (a) and (b).
40
Q.5
(a)
Describe, with the aid of labelled diagrams, the differing geometry of flexural
(parallel) and flow (similar) folds.
Description of each using diagrams.
Quality of the diagrams to show key features (limb and hinge thicknesses, inter
limb angles etc.)
Credit field evidence and examples.
(b)
Discuss the different conditions under which rocks of the same type can
undergo either brittle or ductile deformation.
Reference to:
Brittle and ductile defined. Stress/strain curve. Hookes Law.
Brittle deformation structures (jointing, faulting - related to earthquakes etc.)
Ductile deformation structures (types of folding - flow, metamorphic effects)
Deformation variations in SAME rock type depends upon:
1.
Temperature
2.
Confining pressure
3.
Time
4.
Pore fluids
Stress/strain experiments illustrating above variables
Total 25
GCE Geology MS/(June 2003)
41
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