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2005 Geology
Higher
Finalised Marking Instructions
These Marking Instructions have been prepared by Examination Teams
for use by SQA Appointed Markers when marking External Course
Assessments.
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SECTION A
All questions in this section should be attempted. Forty marks are allocated to this section.
1.
(a)
Marks
Figure Q1(a) shows the atomic structures of quartz and biotite mica.
Figure Q1(a)
Quartz
Biotite mica
Key
tetrahedron of silicon and oxygen (SiO4)
potassium ion
hydroxide ion
iron or magnesium ion
Using diagram Figure Q1(a), explain the following.
(i) Quartz has no cleavage.
No planes of weakness OR
...........................................................................................................................
the arrangement of SiO tetrahedra gives equal strength
4
...........................................................................................................................
in all directions
...........................................................................................................................
1
(ii) Biotite mica has very good cleavage in one direction.
Planes of weakness run parallel to the sheets of SiO
4
...........................................................................................................................
tetrahedra
...........................................................................................................................
...........................................................................................................................
1
(iii) Biotite mica is denser than quartz.
Biotite
contains iron. Its high atomic mass would confer a
...........................................................................................................................
high density on the mineral. OR
The atoms in biotite are more closely packed than in quartz.
Page two
1
(continued)
(b)
Figure Q1(b) shows the radii and charges of some metal ions.
Marks
Figure Q1(b)
150
140
potassium K+
130
120
110
100
Ionic radius (picometres)
1.
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calcium Ca2+
sodium Na+
90
80
iron Fe2+
70
nickel
Ni2+
magnesium Mg2+
60
50
aluminium Al3+
40
30
20
10
0
1
2
3
Positive charge
Use the information in Figure Q1(b) to explain the following observations.
(i) In sodium plagioclase, (NaAlSi3O8), calcium (Ca2+) can completely replace
sodium (Na+).
Calcium ions are the same size as sodium ions. This allows
...........................................................................................................................
them to replace each other.
...........................................................................................................................
...........................................................................................................................
1
(ii) Ores of nickel may form from weathered rock rich in olivine (MgFe)2SiO4.
1 mark
1 mark
2+
The nickel ion has the same size and/or charge as Mg and
...........................................................................................................................
2+
2+
Fe . Thus Ni replaces these ions in olivine. On
...........................................................................................................................
weathering, the Ni remains in the weathered residue.
...........................................................................................................................
Page three
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2.
Marks
Figure Q2 is a map showing an ancient sedimentary basin and surrounding deposits.
Figure Q2
deltaic
deposits
N
desert
sandstones
5
6
4
3
r
nta
e
im
sed
2
n
asi
b
y
1
50 km
marine
shales
(a)
Table Q2(a) shows the numbers of species of animal fossils collected at positions 1–6
on the map Figure Q2.
Table Q2(a)
Type of animal
fossil
Numbers of species at positions 1–6
Position 1
Position 2
Position 3
Position 4
Position 5
Position 6
Ammonites
10
4
2
0
0
0
Bivalves
92
34
15
4
2
0
196
77
22
20
22
10
75
55
30
22
6
0
Crustaceans
Fish
(i)
Give one reason to explain why the numbers of species of animal fossils change
from position 1 to position 5.
Decrease
in number of species because salinity decreases 1 → 5.
...........................................................................................................................
OR
Fewer species can exist in brackish water than in water of
...........................................................................................................................
normal
marine salinity. Accept increasing sediment in water.
...........................................................................................................................
Accept increasing turbidity in water.
Page four
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2.
Marks
(a) (continued)
(ii)
Why does position 6 have the lowest number and variety of animal fossils?
The water here would be hypersaline. Few species can
survive in such conditions. OR
Evaporation of water from this basin would make the water
...........................................................................................................................
...........................................................................................................................
very salty. Few species can live in very salty water.
...........................................................................................................................
1
Accept basin empty at low tide.
(iii)
Fossils of ferns are found only at positions 4 and 5. Give one reason for this
observation.
Ferns are land plants. They have been washed into the
...........................................................................................................................
sedimentary basin by the river which left the deltaic deposits.
...........................................................................................................................
...........................................................................................................................
(b)
1
Which two of the following statements are correct?
A
The greatest percentage change in number of species between positions 1 and 3 is
shown by the bivalves.
B
Bivalves are restricted to only a few habitats because they cannot swim.
C
The greatest percentage change in number of species between positions 1 and 3 is
shown by the crustaceans.
D
Fish are found in the widest range of habitats because they can swim.
E
Crustaceans are the animals which can live in the widest range of habitats.
F
The greatest percentage change in number of species between positions 1 and 3 is
shown by the ammonites.
C
E
Give only the letters: ...................
and ...................




% change = difference × 100 


number at


position 1


Page five
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3.
Marks
Figure Q3 shows a section through the oceanic crust and upper mantle.
Figure Q3
A
sea
level
D
B
E
diorite
magma
C
granite
magma
oceanic
crust
mantle
(a)
Complete Table Q3(a) to match the types of extrusive igneous activity with the positions
marked by the letters A, B, C, D or E.
Table Q3(a)
Type of extrusive activity
Position (Give one of A, B, C, D or E)
Eruption of basaltic lavas not forming pillow lavas
B
Eruption of rhyolites and ignimbrites
E
Eruption of basalt forming pillow lavas
C
Eruption of andesitic lavas
D or A
2
Any two for 1 mark
(b)
Describe the process by which basaltic magma is formed.
Pressure reduction on peridotite
1 mark
...................................................................................................................................
causes partial melting. Partial melt is basaltic magma 1 mark
...................................................................................................................................
...................................................................................................................................
Page six
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3.
Marks
(continued)
(c)
Using diagrams, explain why the oceanic crust on Figure Q3 has areas of normal and
reversed magnetism.
Diagrams
1 mark
Basaltic magma erupted at oceanic ridges cools and acquires
the prevailing magnetic field
1 mark
Since Earth’s field changes basalt erupted at different times may
have normal or reversed magnetisation
1 mark
oceanic ridge
normal magnetisation
⇒
field reverses
⇒
normal magnetisation
reversed magnetisation
field reverses
Stripes of normal and reversed
magnetisation parallel to ridge
3
Page seven
4.
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Figure Q4 shows an ancient ocean environment.
Marks
Figure Q4
reptile
sea
ammonite
crinoid
bivalve
sea floor
(a)
Which animal in Figure Q4 would provide the best zone fossil? Give a reason for your
answer.
Ammonite
Answer .......................................................................................................................
Free swimming and in large numbers would thus be
Reason .......................................................................................................................
common in sediment deposited over a wide area.
...................................................................................................................................
...................................................................................................................................
(b)
2
In the geological timescale, how does a period differ from an era?
An era is divided into periods OR
...................................................................................................................................
Eras are longer than periods
...................................................................................................................................
...................................................................................................................................
(c)
1
Explain the difference between relative and radiometric dating.
Relative dating: putting events in order using cross-cutting and
...................................................................................................................................
superposed relationships
Radiometric dating: using radioactive elements to date a rock,
...................................................................................................................................
mineral or organic material in years
...................................................................................................................................
(d)
1
Why is it difficult to date sedimentary rocks using radiometric dating techniques?
Do not often contain a radioactive mineral formed at the same
...................................................................................................................................
time as the rock OR Sourced from rocks of various ages OR
Consist of minerals, eg quartz, calcite, clay, which have no
...................................................................................................................................
radioactive elements.
...................................................................................................................................
Page eight
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5.
Figure Q5 shows the results of research on a sample of fossil brachiopods of the same
species.
Figure Q5
100
75
Percentage of
surviving
brachiopods
50
25
0
5
10
15
20
25
Age of brachiopods (years)
(a)
Describe the general relationship shown by graph Figure Q5.
Death rate very high among young brachiopods. After the age of
...................................................................................................................................
four, death rate much less. OR
87.5% die by the age of five. From 5–25 the remaining 12.5% die
...................................................................................................................................
off slowly.
...................................................................................................................................
(b)
1
Do the brachiopods shown in graph Figure Q5 represent a life or death assemblage of
fossils? Give one reason for your answer.
Life assemblage
Answer .......................................................................................................................
Reason has to be valid—even if weak
All ages fossilised so has to be a life assemblage OR Only a
Reason .......................................................................................................................
life assemblage would give a smooth, continuous curve OR
This form of curve is shown by present-day populations
...................................................................................................................................
(c)
1
In graph Figure Q5, in obtaining the age of the brachiopods, the scientist assumed that
the ages of the brachiopods are proportional to their lengths. Give one reason why this
might not be true.
Better fed, disease free young brachiopods may be bigger than
...................................................................................................................................
poorly fed, diseased old brachiopods OR
In preset-day populations, age plotted against length gives a
...................................................................................................................................
spread of points. Thus, there is no absolute relationship between
age and length.
...................................................................................................................................
Page nine
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6.
(a)
The graph Figure Q6, shows the total volume of lava from Etna produced during the
last 200 years.
Marks
Figure Q6
2000
1500
Total volume
of lava erupted
since 1800
(millions of
cubic metres)
1000
500
0
1800
1850
1900
1950
2000
Year
(i)
Describe the trends shown by the graph from 1800 to 2000.
1800–1950:
lava erupted at a moderate but constant rate.
...........................................................................................................................
1950–2000: rate of eruption speeded up. Lava erupted at high
constant
rate. OR
...........................................................................................................................
At
1950 rate changed from 5.5 x 106 m3 yr–1 to 23.5 x 106 m3 yr–1
...........................................................................................................................
(ii)
2
What volume of lava was produced each year between 1900 and 1950?
.
6
3
5 5 x 10 m
...........................................................................................................................
Space for working
1950 Total vol = 825 x 106 m3
1900 Total vol = 550 x 106 m3
Volume produced in 50 years = 275 x 106 m3
Volume per year
= 275 x 106 m3
50 years
= 5.5 x 106 m3 yr–1
Page ten
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6.
Marks
(continued)
(b)
Etna has a shape which is nearly conical.
equation.
The volume of a cone is given by this
Volume = 1 × 3 ⋅14 × (radius of the base) 2 × height
3
Etna is 3 km high and the radius of its base is 10.6 km.
Calculate the volume of Etna.
352.5 km3
Accept 352.8 km3
...................................................................................................................................
1
Space for working
V = 1 × 3 ⋅14 × (10 .×6) 2 × 3 km 3
3
(c)
(i) Since records began in 1800, Etna has been producing, on average, 0.008 km3 of
lava per year. Use this figure to calculate the age of Etna.
44057 years
Accept 44 100 years
...........................................................................................................................
1
Space for working
. 6) 2 × 3 km 3= 352 .⋅4575896 km 3
V = 1 × 3 ⋅14 × (10 ×
3
Divide by 0.008 km3 yr–1 gives age = 44057.2 years
(ii) Give two reasons to explain why this may not be the true age of Etna.
• The shape of Etna is not exactly conical so its
volume is not exactly known.
• Using an estimated volume can not give an exact age
...........................................................................................................................
Reason 1 .............................................................................................................
• The average rate of lava production may have been
Reason 2 .............................................................................................................
more or less than the figure given from 1800
•
The rate of 0.008 km3 is an estimate. The average
...........................................................................................................................
rate may have been more or less since 1800.
Page eleven
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7.
Figure Q7 is a field sketch of a rock exposure taken from a geology student’s fieldwork book.
Marks
Figure Q7
greywacke
fossil soil
zone of vesicles
andesite lava
sandstone
metamorphic rock A
zone rich in chromite and
olivine
mudstone with
worm burrows
sill of basic igneous rock
metamorphic rock B
(a)
Give three pieces of evidence suggesting that all the rocks below the lava are the wrong
way up?
Worm burrows
1 Answer ....................................................................................................................
n
Here, they are -shaped. When formed they would be
Reason ....................................................................................................................
U
U-shaped. Thus, they have been inverted.
...............................................................................................................................
Chromite-olivine layer in sill
2 Answer ....................................................................................................................
These are early-formed dense minerals which would
Reason ....................................................................................................................
sink to the base of an intrusion. Here, they are at the
top so the sill has been inverted.
...............................................................................................................................
Cross-bedding in sandstone
3 Answer ....................................................................................................................
When deposited the layering would be concave
Reason ....................................................................................................................
upwards
. Here, the layers are concave
...............................................................................................................................
downwards so they have been inverted.
Accept grain, firming in the wrong direction
Page twelve
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Marks
7.
(continued)
(b)
(i)
Name metamorphic rock A.
Metaquartzite OR quartzite
...........................................................................................................................
(ii)
Name metamorphic rock B.
Hornfels
...........................................................................................................................
(c)
2
Give two reasons to explain how the student would have known that the andesite was a
lava flow and not an intrusion.
• The underlying sandstone has not been metamorphosed.
Reason 1 ......................................................................................................................
Also, the overlying rock has not been metamorphosed.
A sill would have metamorphosed rocks below and
....................................................................................................................................
above.
....................................................................................................................................
• There is a zone of vesicles at the top of the andesite.
Reason 2 ......................................................................................................................
Gas escapes easily from lava so vesicles are
characteristic of lava flows
....................................................................................................................................
• There is a fossil soil on top of the andesite. A sill would
not be exposed to the atmosphere so the andesite forms
....................................................................................................................................
a lava flow.
• The top of the andesite is very
uneven. Lava flows tend to be rubbly
and uneven. Sills tend to have more
even tops.
Section A: Total (40) marks
• The andesite does not transgress into the rocks above
and below. A sill would possibly do this.
Page thirteen
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SECTION B
This section consists of three questions. Only ONE question should be attempted. Fifteen
marks are allocated to this section.
Marks
Candidates should write their answer on pages 15, 16 and 17.
Additional space for answers may be found at the end of this book.
Credit will be given for the use of maps and diagrams.
8.
9.
Write an essay on Earth physics. Give details as follows.
(a)
The types and properties of earthquake waves
3
(b)
The use of earthquake waves in working out the internal structure of the earth
5
(c)
The origin and properties of the Earth’s magnetic field
4
(d)
The origins of the Earth’s internal heat
Write an essay on the formation of ores by surface processes. Give details as follows.
(a)
Placer deposits
3
(b)
Residual deposits
4
(c)
Deposits of iron ore formed in:
(i) Precambrian times
(ii) post Cambrian times
4
(d)
10.
3
(15)
Deposits formed by secondary enrichment
4
(15)
Write an essay on sedimentary rocks. Give details as follows.
(a)
The formation and classification of sedimentary rocks
6
(b)
The formation of sedimentary structures
5
(c)
The environments in which non-marine sediments are deposited
4
(15)
Section B: Total (15) marks
Page fourteen
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SPACE FOR ANSWERS
8.
(a)
Properties of P, S and L waves.
1 mark each
(b)
Changes in speed; reflection; refraction.
Crust, Moho, lithosphere, asthenosphere (LVZ), mantle, outer
core, inner core
10 points, ½ mark each
(c)
Properties: dipole and non-dipole fields, magnetic poles,
reversals, changes in strength
4 points, ½ mark each
Origin: electric currents in outer core. Currents flow generally
→E). Changes in strength and
parallel to lines of latitude (W→
direction of currents cause similar changes in magnetic field.
2 points, 1 mark each
9.
(d)
Decay of radioactive isotopes; heat remaining from origin (KE of
impacting asteroids and mini planets); gravitational energy from
core formation; slowing of rotation.
3 sources, 1 mark each
(a)
Placers—water and wind; locations; properties of minerals
6 points, ½ mark each
(b)
Residual—formed in situ; chemical weathering; formation of Al
and Ni deposits
8 points, ½ mark each
(c)
Iron Ores
(i) Precambrian—BIFs; atmosphere reducing; Fe2+ carried in
solution; precipitated by blue-green bacteria
4 points, 1 mark each
(max: 2 marks)
(ii) Post Cambrian—limonitic bog iron ore formed in swamps;
siderite nodules and bands in Carboniferous rocks; Jurassic
volitic ironstones (chamosite + siderite).
4 points, 1 mark each
(max: 2 marks)
(d)
Secondary enrichment: chemical weathering of chalcopyrite
vein. Cu2+ carried down to water table. Above water table
Cu + CO2 → carbonates. Below water table Cu displaces Fe from
chalcopyrite so copper ore enriched.
4 points, 1 mark each
Page fifteen
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SPACE FOR ANSWERS
10.
(a)
Biological: eg coal, coral limestone
Chemical: eg evaporites, some limestones
Detrital:
eg conglomerate, breccia, sandstones, siltstone,
mudstone.
12 points, ½ mark each
(b)
Descriptions of 5 structures
1 mark each
(c)
Descriptions of 4 environments
1 mark each
Page sixteen
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SPACE FOR ANSWERS
Page seventeen
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SECTION C
All questions in this section should be attempted.
section.
11.
Forty marks are allocated to this
Marks
Look at photograph Q11 below.
Photograph Q11 (An aerial view of a desert landscape)
A
Road
(a)
Identify geological feature A.
Alluvial fan
...................................................................................................................................
(b)
1
Using diagrams, explain how this feature was formed.
Flash flood produces sediment-laden stream which changes
speed on running from canyon onto flat valley floor. Distributaries
deposit sediment in fan shape.
coarse-grained
sediment
fine-grained
sediment
Layering
from
repeated
flash floods
Explanation 1 mark
Diagrams 1 mark
sediment becomes finer towards fan margin
2
Page eighteen
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12.
Marks
Look at photograph Q12 below.
Photograph Q12
All
exposure of
volcanic
ash
0
10
cm
(a)
Identify the geological feature shown in Photograph Q12.
Volcanic (breadcrust) bomb, pyroclast, lava bomb
...................................................................................................................................
(b)
1
Using diagrams, explain how this feature was formed.
A mass of liquid but viscous lava thrown from a volcano acquires
a round shape in flight. On cooling, the bomb forms a hard skin.
On further cooling the hard skin is broken and pushed apart by
expansion of the bomb interior. Expansion caused by release of
gas and formation of vesicles.
Explanation 1 mark
Accept origin of pyroclastic material
Diagrams 1 mark
for explanation 1 mark
lava rounds
off in flight
solid
hard skin forms
as bomb cools
inside expands
as gas released
liquid
bomb
vesicles
volcano
solid skin broken
and spread
ash
Page nineteen
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13.
Study the map Figure Q13 on the separate worksheet and answer the questions based on it.
(a)
(i)
How many unconformities are shown?
Two
...........................................................................................................................
(ii)
1
In which direction does the fold plunge?
South
...........................................................................................................................
(b)
Marks
1
On which side of fault F1 have the rocks moved up? Give a reason for your answer.
West
Answer .......................................................................................................................
Gneiss abuts on younger sedimentary rocks so west side
Reason .......................................................................................................................
must have moved up
...................................................................................................................................
(c)
2
Which statement is correct?
A
Both F1 and F2 are normal faults.
B
F2 is a normal fault; F1 is a reverse fault.
C
Both F1 and F2 are thrust faults.
D
F2 is a reverse fault; F1 is a normal fault.
E
Both F1 and F2 are reverse faults.
D
Give only the letter: ....................
1
Error on map
Felsite should cut breccia
Page twenty
Page twenty-one
X
F1
F2
shale
siltstone
F1 - 1 mark
F2 - 1 mark
anticline - 1 mark
breccia and arkose - 1 mark
relationships under - 1 mark
breccia
arkose
breccia
conglomerate
Figure Q13(e)
felsite
dolerite
metamorphosed
dolerite
gneiss
Key (Rocks not in order of age)
fault with dip of
fault plane in
degrees
directions of
strike and dip
30 with dip in
degrees
F1
55
P
Y
Position P: Junction between
dolerite and metamorphosed
dolerite
dolerite
metamorphosed
dolerite
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13.
(continued)
(d)
Figure Q13(d) shows a junction between dolerite and metamorphosed dolerite at
position P on the map Figure Q13.
Figure Q13(d)
dolerite
metamorphosed dolerite
mineral C
3 mm
mineral A
(i)
mineral B
junction
Name minerals A, B and C.
pyroxene
Mineral A ...............................................................
plagioclase
Mineral B ...............................................................
amphibole or hornblende
Mineral C ...............................................................
(ii)
3
Explain why the metamorphosed dolerite shows no foliation close to the dolerite.
Gneissose
metamorphosed dolerite has been subjected to
..........................................................................................................................
contact
metamorphism by dolerite. Contact metamorphism
..........................................................................................................................
(e)
takes
place under hydrostatic pressure so foliation destroyed.
..........................................................................................................................
1
On the topographic profile Figure Q13(e) (on the separate worksheet), draw a
geological section between points X and Y on the map Figure Q13.
5
Page twenty-two
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13.
(continued)
(f)
Write a geological history of the area shown on the map, Figure Q13.
Rock of unknown type intruded by dolerite
Regional metamorphism then intrusion of dolerite
Uplift, erosion
Deposition of conglomerate, siltstone, shale
above unconformity
}
1 mark
}
1 mark
Folding
1 mark
Uplift, erosion
Deposition of breccia and arkose above unconformity
}
1 mark
Faulting
1 mark
Intrusion of felsite
1 mark
6
Page twenty-three
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Marks
On the map Figure Q14, a thin coal seam of uniform dip outcrops at A, B and C.
Figure Q14
600 m
60
0
40
0
C
0
400 m
40
300 m
0
B
200 m
0
30
0
20
N
500 m
50
30
0
100 m
100
0
20
A
500 m
Key
0
C
10
14.
outcrop of coal seam
surface contour with height in metres
(a)
Draw structure contours for the coal seam onto the map Figure Q14.
2
(b)
Draw in the outcrop of the coal seam onto the map Figure Q14.
2
(c)
Calculate the angle and direction of dip of the coal seam.
30–35 °
Angle ...................
south
Direction of dip ...................
2
Space for working
500 m ≡ 34.3 mm
10.8 mm ≡ 500 x
157.43
32.4 °
10.8
34.3
≡ 157.43 m
100
10mm
145.77
34.45 °
Page twenty-four
15.
Study the map Figure Q15 and answer the questions based on it.
Figure Q15
500
600
700
800
900
1000
1100
900
N
800
800
700
600
600
700
800
300
600
600
L
900
1000
900
800
700
600
500
400
0
90
N
100
700
500
0
80
M
70
500
700
0
1000
1000
900
900
800
800
700
700
600
600
500
500
400
400
60
0
50
0
700
800
Key
400
500
600
700
800
surface contour with
height in metres
00
50
0
600
900
0
8
1000
200
400
metres
borehole
L
300
borehole with depth to
coal seam in metres
500
500
structure contour
for fault plane with
height in metres
depth from
surface to
coal seam
Page twenty-five
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15.
Marks
(continued)
(a)
(b)
Structure contours have been drawn for a fault of uniform dip. Draw in the outcrop of
the fault plane.
2
A thin coal seam of uniform dip is found in boreholes L, M and N at the depths shown
from the surface.
(i) Draw structure contours for the coal seam over the whole area of the map.
Number the structure contours north of the fault.
3
(ii) Draw in the outcrop of the coal seam on the north side of the fault.
1
(iii) On the south side of the fault, the coal seam is 100 m lower than it is on the north
side of the fault. Number the structure contours on the south side of the fault.
1
(iv) Draw in the outcrop of the coal seam on the south side of the fault.
1
Section C: Total (40) marks
[END OF MARKING INSTRUCTIONS]
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