ERC/KS3/Ex

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The Ercall, Shropshire

KEY STAGE 3 EXERCISES
© GeoconservationUK ESO-S Project, 2014


It is anticipated that the ideas and materials presented here will be adapted by schools, and others, to be more appropriate for their own purposes and programmes of study.

In such circumstances please acknowledge the source as the Earth Science On-Site project.

Key Stage 3 Downloads
Pupil Worksheet (pdf file, 348 KB)
KS4 Pupil Worksheet (pdf)

Contents

Introduction

In order to complete these field work exercises you will need to ensure: each pupil is provided with a clipboard and copies of the worksheets; each small work group of pupils has a tape measure, a hand lens, a grain size comparator card (or graph paper), a clinometer and a compass.

In addition group leaders will need a small plastic bottle of water to demonstrate porosity and permeability.


To get to the quarries from the Forest Glen car park it is necessary to walk northwards along Ercall Lane, about 500 metres. This road is narrow, with no footpaths, so remind everyone to take care.

Access to The Ercall quarries is through a barrier on the east (right), signposted by a Wildlife Trust marker “ERCALL WOOD NATURE RESERVE”.

Follow the path between the quarries not used in this itinerary, until you come to quarry 1. This is both locality “A” and “F”: the start and finish of the Key Stage 3 itinerary. See Figure 1.

ERC7locKS3.jpg
Figure 1: Locality Map for The Ercall

Quarry 1

Looking to the north-east from the engraved rock on the left of the path (M.R. SJ 643 095) Time: 10 minutes

Locality “A”

This view point is the entrance to quarry 1. Do not enter the quarry from here. From this point there is a view of one of the Ercall quarries, which were worked for aggregates until 1986. In 2000 the land was bought by the Shropshire Wildlife Trust to set up the Ercall Local Nature Reserve.

There are a number of reasons for visiting this locality: the viewpoint gives an introduction to the quarry and allows the pupils to see the scale of the quarry. Another reason is to allow the teacher to point out part of the route that the pupils will follow as they carry out their fieldwork around the quarry.

ERC7LocaQuarry.jpg
Figure 2: View From Locality “A” Towards The North East

Activity 1

Possible questions/tasks Possible answers

(words in brackets indicate need or opportunity for further teaching)

Q1. Describe the shape of the quarry. Roughly rectangular.

Wider than it is deep.

(Although it is difficult to estimate the size of the quarry from this view point, the map shows the quarry is about 100m wide.).

Q2. On the evidence of different colours seen in the quarry face, how many types of rock appear to be in this quarry? Two. (The two colours you can pick out are pink and light grey)
Q3. Can layers be clearly seen in the light-grey coloured rock in the quarry? Yes. (The layers can be seen best on the right hand side {eastern part} of the quarry. These layers are not horizontal, they are tilted at an angle).
Q4. Can layers be clearly seen in the pink coloured rock in the quarry? No. (This pink mass of rock is cut by fractures, giving it a blocky appearance, and doesn’t show layers).
Q5. Predict whether either of the rocks in this quarry is likely to be sedimentary or not. Layering is often sedimentary bedding so the grey coloured rock is most likely to be sedimentary.
Explain that the pupils will return to this view point after a walk around the quarries.

Point out that they will take a path to the east that will lead them to the upper part of the quarry. (Here they will be able to look more closely at these pink & grey coloured rocks - & the contact between them). Point out that on their walk around the quarries they will be looking for evidence showing how the rocks formed within the rock cycle.

 

Locality “B”

Quarry 2 Looking To The North-East From The Stile On The Path (M.R. SJ 644 095) Time: 20 minutes

Continue along the path past locality “A”, taking the bend to the north to locality “B”. This is by the stile in the fence across the path. From this point there is a view of one of the lower Ercall quarries. This quarry was worked for a rock called Wrekin Quartzite. The sandstone in the Wrekin Quartzite could be broken into pieces and used as an aggregate because it is a chemically and physically resistant rock.

[NOTE: The “Wrekin Quartzite” includes sedimentary conglomerate and a quartz rich sandstone cemented by silica.]

ERC7localb.jpg
Figure 3: The View From Locality “B” To The North East

Activity 1

Possible questions/tasks Possible answers

(words in brackets indicate need or opportunity for further teaching)

Q1. Describe the shape & estimate the size (height, length & width) of the quarry.

(Clue: the average height of a teacher is 1.7m).

Approximate rectangular shape.

Size estimates will vary!

Approximate size: 50m high, 50m wide, 100m long

Q2. Describe the layering seen in the quarry. The layers are tilted at an angle.

There are thin & thick layers

(The layers are called beds; layers are separated by bedding planes).

Q3. Observe the rocks in the different beds.

What differences do you see?

Some rocks are darker in colour.

Some beds are stained with a yellow / orange colour.

The rocks break up or weather in different ways in different beds.

Some bedding planes (on the left hand side) are not flat and smooth but show parallel ridges.

(These ridges on the bedding planes are called ripple marks, as will be seen later).

Q4. Which of the main rock groups occurs in this quarry? (Igneous, metamorphic, sedimentary). Sedimentary

(The layering is sedimentary bedding)

Q5. Would these rocks have been formed as horizontal beds? Yes – they were formed on the sea bed so they would have been deposited as roughly horizontal layers. (Principle of Original Horizontality)
T1. Ask pupils to estimate (a) the angle of tilt of the beds & (b) the direction they are tilted towards.

(The angle of tilt from the horizontal is usually called the angle of dip. True Dip is the direction of the steepest angle down the bedding plane).

45-50° tilt (angle of dip)

Tilted towards the south east

Q6. Ask pupils if they can explain how the original horizontal layers became tilted in this direction. The tilting of large volumes of rock would require vast amounts of energy and the only known explanation involves tilting by earth movements, caused by Plate Tectonics.
Q7. Can you see any cracks across the layers? Yes. (Cracks are called joints or fractures)
Q8. Can you suggest how these cracks may have formed? Most probably formed during earth movements (uplift).

(Take other suggestions e.g. quarry blasting)

Q9. Look towards bedding planes showing ripple marks on the left / west side of the quarry. What can you see below the quarry face here? Broken/angular rock fragments. Heaps of broken rock. (The heaps of rock fragments form a localised scree slope).
Q10. Can you suggest where these rock fragments came from? Weathering of rock layers above.

(The rock fragments are angular and were probably weathered by physical weathering [freeze/ thaw weathering produces angular fragments]. These fragments have remained angular because they have not moved far [have only moved here by gravity]).

T2. Ask pupils to complete and label the field sketch on worksheet 1 (pdf file, 151 KB)  
Point out pupils will now look more closely at the rocks in this quarry.  

Locality “C”

On The Floor Of Quarry 2 At The Warning Signpost On The Quarry Floor (M.R. SJ 644 096) Time: 15 minutes

A Cross the fence by using the stile and advance up the slope to the warning sign which is locality “C” ( See Figure 1.) Stop at the warning sign. There is no need to go nearer to the quarry faces. Loose pieces of rock can be picked up from the quarry floor here for pupils to test and look at.

Explain that the exercise here (and at locality “Ei”) is to compare two different sedimentary rocks and summarise the information on worksheet 2. Point out that these rocks can be traced uphill from this quarry into the quarry they viewed at locality “A” at the start of their field visit.

Activity 1

Possible questions/tasks Possible answers

(words in brackets indicate need or opportunity for further teaching)

T1. Look at loose blocks and pieces of rock on the quarry floor. Collect a loose sample of sandstone.

Describe the colour and feel of the rock when you rub your fingers over its surface.

(NOTE: Conglomerate is a rock that has grains more than 2mm in size; sandstone is the rock that has grains between 0.06 & 2mm in size).

The rock is white to light grey colour. Shows some staining - mostly yellow-brown.

It feels rough to the touch.

The grains don’t rub off which means they are strongly held together i.e. are well-cemented.

T2. Use a hand lens to look at the size of the grains.

Are the grains about the same size?

Responses will vary depending on the sample chosen, but most of the grains are about the same size. (The grains are about the same size {like sugar grains} so the rock is described as well sorted).
T3. Compare the grains against a sheet of 1mm graph paper, or a grain size comparator card.

What is the average size of the grains?

Identify the rock

Estimated grain size = 0.5mm.

A sandstone (cemented grains less than 2mm in size).

Q1. Now relate to what we saw in the class demonstration to the size of the sandstone grains.

Was the deposit laid down in low, medium or higher energy conditions?

Medium to low energy conditions.
T4. Use a hand lens to look at the shape of the grains.

Are the grains rounded, angular or between rounded and angular?

[NOTE: “Rounded” does not mean “spherical”. It means there are no sharp edges, whatever shape the grain happens to be.]

Responses will vary depending on the sample chosen. Most grains are between rounded & angular, but are nearer rounded than angular).
Q2. Now relate to what we saw in the class demonstration to the grain shape.

What does the grain shape tell you about the amount of time over which the grains were transported?

Grains, originally angular, abrade (rub against) one another as they are transported and the longer the process of transportation goes on the more rounded they become.

[NOTE: This may or may not mean transport over a long distance. For example, if movement is up and down the same beach.]

Q3. Are most of the grains made of the same mineral?

What is the evidence?

Yes - on the basis of similar colour (pale or clear) and similar hardness (scratch steel).

(Most of the grains are made of the mineral quartz.)

T5. Use the water dropper bottle and ask pupils to observe. Does a small drop of water sink in or run off the surface of the rock?

What does this tell you about the rock?

Water runs off the rock surface

It is a non porous rock.

(It does not allow water to pass through it so it is an impermeable rock, although water may pass through the bed along joint planes).

Q4. Can you see any fossils in the rock?

What does this tell you about the rock?

No fossils seen, so this does not tell you very much.

Perhaps organisms (a) couldn’t live in the environment at the time the rocks formed or (b) weren’t preserved, either because their hard parts were destroyed during transportation, or they were soft bodies organisms with little chance of being fossilised.

T6. Ask pupils to complete the part of the table summarising the evidence for the sedimentary processes that probably formed the sandstone. Refer to the relevant part of the completed worksheet 2 for sites C & E. (See pupil worksheets pdf file, 348 KB)

Locality “D”

At A Warning Sign On A Track Along A Bench (A Quarry Level) On The North Western Side Of Quarry 2 (M.R. SJ 644 096) Time: 10 minutes

Locality “D”. Turn south west from locality “C” andfollow the path rising from the quarry floor. The path passes alongside the bedding planes dipping at 45º SE. Stop on the path at the warning sign. Point out the need for care close to steep slopes. Do not allow climbing on the quarry faces. Explain that there is more evidence to be investigated here that the rock is a sedimentary one and not a metamorphic “quartzite”.

500


ERC7ricksripples.jpg
Figure 4 and 5: The Sloping Bedding Plane With Ripple Marks At Locality “D”

Activity 1

Possible questions/tasks Possible answers

(words in brackets indicate need or opportunity for further teaching)

T1. Measure the dip amount and direction of this bedding plane.

TIP: Use a clipboard to get an appropriate plane surface for measurement. First use the clinometer to find the “horizontal” across the bedding plane (dip= 0 degrees), then measure the true dip at right angles to this horizontal.

Dip measurements, depending on exactly where they are taken should be close to 45-50° tilt (angle of dip) towards the south east, or 135 degrees magnetic.

(This is an optional activity, if the instruments are available. If so add 15 minutes to the time for the activity. If not draw attention to the dip and lead into the next question).

Q1. Are the beds here older or younger than the rocks you can see on the opposite (south east) side of the quarry?

What is the evidence?

Older. The layers at this locality are tilted to the SE so these beds must lie below the rocks on the opposite side of the quarry.

(The Principle of Superposition: in a succession of sedimentary layers, the oldest layers were deposited first and are found below younger layers, which were deposited later).

T2. Observe the ripple marks on one of the bedding planes.

What do you notice about:

  1. their shape (in plan view & in cross sectional view)?
  2. their spacing?
  3. their height?

(Refer to Pupil worksheet 3)

  1. Ripples in plan view have the shape of long & narrow ridges. In cross section they often have one side slightly steeper than the other i.e. have a slightly asymmetrical shape.
  2. Ripples approximately evenly spaced.
    (The average ripple wavelength is approximately 170mm)
  3. Ripple height is approximately 15mm.
Q2. Are the ripple marks running in the same direction? Yes – the ridges roughly run in the same direction.
Q3. Where can you see ripple marks forming today?

(Possibly relate to what they saw in the class demonstrations about how ripple marks can be formed).

Ripple marks are formed by wind or water currents moving over loose sandy sediment on the sea floor: on beaches, on top surfaces of river deposits, on surfaces of sand dunes in deserts, or by wave action in seas or lakes. They can be formed by oscillating wave action or flowing currents.

[NOTE: These ripples are likely to have been formed in moving water, not wind, as the Ripple Index is less than 15.]

Q4. Why may this sort of information about ripple marks help you to work out how this particular rock was deposited? By comparison with ripples forming today. (See the response to Q3).

The Principle of Uniformitarianism (The present is the key to the past): the biological, physical & chemical processes we see today, operated in much the same way in the past).

T3. Ask pupils to complete the worksheet 3 for locality “D”. Refer to the completed worksheet for locality “D” in the teachers’ notes

Locality “Ei”

View Of The Quarry Face In Quarry 1 Looking North East From A Point Close To The Information Plaque (M.R. SJ 644096) Time: 20 minutes

Follow the path back to the floor of quarry 2 and take the track to the north. The track climbs uphill, heading towards the lower part of quarry 1 and passes alongside the edge of the quarry.Stop at the warning sign near the information plaque. Keep to the path and do not climb over the barrier fence or onto the quarry faces. Loose pieces of rock can be picked up from the path here for pupils to examine.

ERC7f6.jpg
Figure 6: View Of The Quarry Face At Locality “Ei”

Explain that at locality “Ei” the exercise is to complete the comparison between two sedimentary rocks (Worksheet 2) which was started at locality “C”. First find loose specimens of a sedimentary rock which is not sandstone.


ERC7f7.jpg
Figure 7: Hand Specimen of Conglomerate


ERC7f8.jpg
Figure 8: The Conglomerate In The Quarry Face


ERC7f9.jpg
Figure 9: Igneous Rock (Granophyre)

Activity 1

Possible questions/tasks Possible answers

(words in brackets indicate need or opportunity for further teaching)

T1. Look at the loose blocks and pieces of rock on the path. Collect a loose sample of a rock which is different from the sandstone at locality “C”.

(It’s a conglomerate. Clue:Conglomerate is a rock that has grains more than 2mm in size).

Describe the colour and feel of the rock when you rub your fingers over its surface.

Light grey colour. Shows some staining (yellow-brown or green).

Feels rough to the touch.

The grains don’t rub off and are strongly held together i.e. they are well-cemented.

T2. Use a hand lens to look at the size of the grains.

Are the grains about the same size?

No, they are of different sizes.

(The grains are of different sizes so the rock is described as poorly sorted. Grains are a mixture of pebbles (grains 4→64mm across) and granules (grains 2→4mm across).

T3. Compare the grains against a sheet of 1mm graph paper, or a grain size comparator card.

What is the average size of the pebbles?

Responses will vary depending on the sample chosen.

Estimated average grain size in the range 15 to 50mm. (They are described as coarse sized grains).

Q1. Relate to what we saw in the class

demonstration to the size of the grains in the conglomerate

Was the deposit laid down in low, medium or higher energy conditions? (Give a reason for your answer).

Higher energy conditions.

It takes more energy to move larger (and therefore heavier) grains and pebbles.

T4. Use a hand lens to look at the shape of the grains.

Are the grains rounded, angular or between rounded and angular?

Identify the rock.

Responses will vary depending on the sample chosen. Most grains are between rounded & angular. (The grains are described as sub-angular to sub-rounded).

It is a sedimentary rock (conglomerate) made of cemented, sub-rounded grains bigger than 2mm in size.

Q2. Now relate to what we saw in the class demonstration to the grain shape.

What does the grain shape tell you about the length of time over which the grains were transported?

Since grains start off angular but abrade (“knock the corners off”) one another as they are transported, then they become progressively more rounded the longer they are moved about. This means these grains were not transported for the huge periods of time which would have produced well rounded grains.
Q3. Most of the pebble-sized grains are pieces of rock. Are these pebbles made of the same type of rock?

Give the evidence for your answer.

No - on the basis of different colours (striped red/pink, pale grey, black, red/pink or green) and different patterns in the pebbles (e.g. banding/ no banding) they are of different rock types.

[Most of these grains are pebbles of the following rocks: rhyolite {striped red/pink}, quartzite {pale grey}, igneous rock {black}, and more rare granophyre {dark red}].

NOTE: Law of Included Fragments: fragments are always from rocks older than the rocks in which they occur.

Q4. Can you see any fossils in the rock?

What does this tell you about the rock?

No fossils seen. This tells us very little.

It may be that organisms (a) couldn’t live in the environment at the time the rocks formed or (b) were not preserved because they were soft bodied, or their hard parts were easily broken up by pebbles rolling over them.

T5. Use the water dropper bottle. Does a small drop of water sink in or run off the surface of the rock?

What does this tell you about the rock?

Water runs off the rock/ doesn’t sink in

It is a non-porous rock.

(It doesn’t allow water to pass through it so it is a non-porous & impermeable rock).

T6. Students asked to complete part of the table on worksheet 2 summarising the evidence for the sedimentary processes that probably formed the conglomerate. A completed worksheet 2 for localities “C” & ”E” can be found in the Pupil Worksheets (pdf file, 348 KB)

Locality “E(ii)”

From the warning sign and information plaque retrace your steps and follow the path downhill for about 3 metres until you reach a low quarry face to your left running parallel to the path on its eastern side. Stop at this point. Make sure you stay on the path. There is a steep slope away from the path to the south west. At this point here is a good view of the contact between the granophyre and the conglomerate.

The activity at locality “Eii” is to examine the contact (or line of separation) between different rock types. The nature of “contacts” between rocks is an important piece of evidence for Earth Scientists in their interpretation of events. They ask questions like “Is this contact: a bedding plane?; or is it cross-cutting?; or is it intrusive?; or is it faulted?; or is it caused by erosion?”.

Explain that pupils will inspect the contact between the pink rock (granophyre) and the Wrekin Quartzite and complete Worksheet 4 here. (See the Key Stage 4 pupil worksheets] and Teachers' Notes for completed examples of the worksheets).

Activity 2

Possible questions/tasks Possible answers

(words in brackets indicate need or opportunity for further teaching)

Q1. Closely observe and describe the rock in the upper part of the quarry face.

(Hint: You will need to get very close to the rock face to see the details of the rock composition. See Figures 7 and 8).

Layering: shows thick and thin layers; layers tilted to the south east.

Colour: light grey

Composition: made up of pebbles

Q2. What is the rock type in the upper part of the quarry face? Sedimentary Conglomerate.
Q3. Observe and describe the rock in the lower part of the quarry face. It is not layered, but it breaks along joints.

Colour: dark pink/red

Composition: interlocking crystals, not pebbles or grains

Q4. What is the rock type in the lower part of the quarry face? An igneous rock (called Granophyre).
T1. Collect a loose sample of granophyre. Use a hand lens to look at the shape and size of the crystals in the rock.

Are the crystals about the same size?

The crystals have irregular shapes & interlock (fit together like the pieces of a jigsaw puzzle).

(Two different minerals form the crystals in granphyre: quartz {greasy-looking and a pale grey colour} and feldspar {pink}). (See figure 9)

Responses will vary depending on the sample chosen.

(In most samples the crystals are approximately the same size, showing the crystals formed in a single stage of cooling. Occasionally samples show a few crystals larger than others, indicating that the magma may have cooled in two stages. {Initial slower cooling formed larger crystals}). See Figure 9

T2. Compare the crystals against a sheet of 1mm graph paper. What is the average size of the crystals? 2mm. (Crystals of this size are described as medium sized crystals)
Q5. Relate to what we saw in the class demonstration to the size of the crystals in the granophyre.

What does this crystal size tell you about how this igneous rock formed?

The rock formed as a magma cooled down and crystallised. The medium crystal size indicates speed of cooling, so it can be inferred that this magma cooled more slowly than an extrusive lava, with fine crystals but more quickly than in a large intrusion (batholith) with coarse crystals.
T3. Encourage pupils to find and put a hand on: a bed, a bedding plane, a joint, the boundary (or contact) between the conglomerate and the granophyre. Explain that the kind of contact (boundary) between rock types is very important evidence and we need to look at the contact as much as we look at the rocks themselves.
Q6. What do you notice about the contact between the conglomerate and the granophyre? It is tilted very steeply to the south east.

It is uneven and not flat or planar.

  Stages in the formation of the unconformity

A

245

B

245

C

245

D

245

E

245
Q7. Can you suggest reasons why a) the unconformity is uneven and b) the unconformity and the layers above it are no longer roughly horizontal? The original erosion surface was irregular.

Earth movements have tilted the unconformity and the rock layers.

T4. Ask pupils to complete the worksheet 4 for locality “E”, Activity 2. Refer to the completed worksheet 4 for locality “E”, Activity 2. (See ERC8 Pupil Worksheets pdf file, 348 KB)

Locality F

Quarry 1 Looking North East From The Engraved Rock To The Right The Path (M.R. SJ 643 095) Time: 15 minutes

From locality “E” follow the path, carefully, back down the slope. Approach the fence and cross the stile marking locality “B” and retrace your steps to return to the engraved rock beside the path, locality “A”, (which is also locality “F”). Stop at this view point.

Explain that at locality “F” the pupils will complete a field sketch of the view of quarry 1 looking to the north east.

ERC7f10.jpg
Figure 10: View of Locality “E” From Locality “F”

Activity 1

Possible questions/tasks Possible answers

(words in brackets indicate need or opportunity for further teaching)

T1. Allow pupils to view the quarry.  
Q1. Relate the features to what they saw in their walk around the quarries and summarise their observations so far.

What did they find out about:

  1. the pink coloured rock and how it formed?
  2. the grey coloured rock and how it formed?
  3. which of these two rocks formed first? (Ask for the evidence)
  4. The contact between the pink coloured rock & the grey coloured rock?
  1. Made up of interlocking crystals and has joints but no bedding. This is therefore an igneous rock (called granophyre) formed by the cooling of magma
  2. Made up of grains, showing bedding and ripple marks. This is therefore a sedimentary rock, (conglomerate and sandstone).
  3. Granophyre, because the conglomerate and quartz sandstone lie on top of it and the conglomerate contains some pebbles of granophyre.
  4. It is uneven, formed by erosion before the grey rock was deposited. It is an unconformity
T2. Ask pupils to complete the field sketch on worksheet 5, of quarry 1 looking to the north east from this view point. A field sketch is included on the completed worksheet for locality “F” and can be found in the Pupil Worksheets (pdf file, 348 KB).
T3. Draw pupils’ attention to the information board that is close to the path and approximately 20 metres to the right of the view point at the engraved rock. This board gives the information they will need to complete worksheet 5.

(Pupils may wish to read the information on the board and make additional notes about the Ercall quarries).

A table summarising some of the information about the Wrekin Quartzite & the granophyre is shown on the completed worksheet for locality “F”. (See Teachers' Notes )


Return to the path and on to Ercall Lane. Turn left and proceed back to the Forest Glen car park.

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