WJEC GL4 Feedback 2006

Principal Examiner

Ian G. Kenyon

Mark Range

25 to 90 out of 96

An accessible paper with only 46 of the 819 candidates scoring less than 40 out of 96

Areas of Weakness

Poor understanding of the formation of cross bedding and the internal structure of a dune

Diagenetic changes poorly understood, actual process names rarely stated

Many candidates were unable to suggest reasons to explain the lack of fossils

in the sedimentary sequence

Question 1: Sedimentary Rocks

Current direction incorrect by 180º

Internal stratification incorrect

No scale indicated on sketch

Wind/current direction incorrect by 180º

Internal structure confused

Absence of any scale on sketch

Only annotation refers to marine processes

A Good Answer!

Internal structure correct

Current direction appropriate

Dune migration correctly plotted

No scale indicated though!

Question 2: Palaeontology

Areas of Weakness

Some candidates only drew planes of symmetry on either specimen A or B

A number of candidates failed to identify the fossil groups. Howlers

included ammonite and tripod!

Shell morphology and mode of life poorly understood. Many contradictory

statements made here.

Line of symmetry on brachiopod incorrect.

Fossil groups named as geological periods!

A Good Answer!

Byssus confused with limbs here!

Specimen Y was often confused with Pecten as well as Pecans!

Question 3: Metamorphism

Areas of Weakness

Lack of explanation of origin of texture 3b. Many students simply

described the texture

Inability by many to describe two simple practical tests to distinguish between marble and metaquartzite

Limited understanding by many of the conditions of dynamic metamorphism

Answers to this question revealed glaring gaps in very basic geological knowledge by many candidates!

Quartz has cleavage!

Too easy for A2? It proved to be a really good discriminator!

Many candidates failed to link marble with calcite and metaquartzite with quartz to devise simple

practical tests to distinguish them apart.

Question 4: Structural Geology

Areas of Weakness

Drawing of Interlimb angle, overturned limb and cleavage/bedding intersection

poorly attempted by many

Amplitude is not understood by the majority of candidates

Many students are poor at evaluating geological statements. They seem to agree

or disagree with everything or contradict themselves time and again.

A typical answer scoring half marks

Only part of the interlimb angle

is indicated

Axial plane most commonly plotted

correctly

Bedding/cleavage intersection is

pointing to the middle of the bed

All 4 items plotted correctly for 2 marks

Amplitude

The same mistakes made as in previous years

Candidates simply measured the distance between the crest

and trough of the fold

Amplitude is half the distance between crest and trough

Not the perfect answer but a good attempt at an evaluation and worth full marks!

This question was another good discriminator.

Section B – BGS Mapwork

Key to symbols omitted

Slight difference in colour between map and generalised vertical column

Metamorphic aureole symbol rather faint

Candidates did not seem to be disadvantaged by this!

Question 5 (a) (i)A number of candidates regularly fail to realise that

two directions are required for the strike credit

A small hyphen was inserted in the response box to help candidates!

A small number of candidates took this as a signal to leave the box blank!

Question 5 (a) (ii)Description of folding in box A was

well done by many candidates

Weaker candidates failed to refer to symmetry or quote dip values and strike orientations

Only the better candidates referred to a basin structure or plunge directions

Question 5 (b)A good understanding shown here by many candidates.

Graben structure recognised by the majority with the central block being downthrown between 2 parallel faults

A small number of candidates found it a challenge however-see below!

Question 6 (a)Generally well answered but the answers

for the angle of dip of the Ochil Fault were bewildering at times and included:

7, 15, 45, 99, 105, 115, 129, 145, 171 degrees

Only a minority of candidates noticed that the vertical scale had been exaggerated by x 2

Credit was given for reference to apparent dip as the section may not have

been at right angles to the fault plane

Question 6 (c)

The examiners appreciate that the size of the boxes restricted candidates from giving fully detailed reasons.

A few candidates mistakenly reasoned the relative ages of the three boxes rather than each of the pairs in turn!

Question 7 (a)The majority of candidates identified (H) Pluton and (P) Dyke

The better candidates drew clear cross sections to explain how the angle of the contact affected the width of the aureole

Question 7 (b)Some excellent answers here with very detailed annotations

Some candidates mixed up baked and chilled margins

A small number of candidates left this completely blank

Question 8

Some candidates gave non-geological factors for which little credit could be given

Reference to noise, air quality and eyesore were common errors

The label on the cross section reading ‘superficial deposits not shown on the map’

seemed to cause confusion among some candidates when evaluating site G

Question 8

Some candidates ignored ‘landfill’ and referred to problems of opening up the

quarry for further extraction of rock

Most candidates decided either good or bad for each site rather than evaluating all the evidence

Candidates should be aware that all sites have the potential to be a landfill site if there is sufficient engineering employed-e.g. clay liner

Question 8

Good discussion of geological factors included:

Rock permeability and dip direction of beds

Synclinal structure of argillaceous rocks

Possibility of fault reactivation

Mining history and potential for subsidence

Impermeability of igneous rocks

Very few candidates attempted to put the three sites in a possible rank order from most to least suitable

Some candidates were quite appreciative of the examiner’s efforts in marking their papers

The End