KNO/KS3/Ex/4

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Knowle Quarry, Shropshire

KEY STAGE 3 TEACHING TRAIL: SITE 4
© 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.

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Key Stage 3 Downloads
Pupil Worksheets (pdf file, 769 KB)
Group Leader Notes (pdf file, 986 KB)

Site 4: Knowle Quarry (west)

Take the group on the path away from the ridge, a right fork, along the Lime Kiln Walk. The wide and surfaced path, suitable for wheelchairs, then gives way to a narrow track, off to the left, parallel to the road. After 200 metres the path descends a flight of wooden steps into Knowle Quarry. These steps can become very slippery when wet, so descend with care. At the bottom of the steps turn immediately to the right to find the southern face of the quarry. This is Site 3. It is owned by The National Trust and is a protected site. There is no need to damage the face, as specimens may be found along the foot of the face. Please do not remove them from here, as opportunities for some collecting occur later.

KNO7f8.jpg
Figure 8: Site 4. Knowle Quarry (west)
Take the path from the bottom of the steps, northwards for 20 or 30 metres and stop the group where there is a good view of the face to the west (left).

Do not cross the fence or approach the face.

Here ask the group to recall and apply the ideas they have used at Site 3 about reef development.

First focus attention of the rock type and the evidence it contains of the conditions at the time of deposition (about 400 million years ago).

Suitable questions at this site Acceptable responses
Describe the differences between the upper and lower parts of the face. Upper parts are thinly bedded and appear almost horizontal (in fact they are dipping slightly towards you, but it is hard to see from this angle.)

The lower parts are un-bedded “ballstone” reef.

Describe the top surface of the “ballstone” reef. It is almost horizontal with two coral “mounds” on the left. (The beds above have been compacted during burial, over the corals, they have not been folded.)
What does this mean about when growth on this reef ended? It all died back together, at the same time and does not re colonise higher up the face.
Tell the group that the black line on the worksheet sketch is a layer of volcanic ash. Ask how this might be related to the ending of the reef growth? Volcanic eruption (from a place not identified) created ash clouds which were blown across the sea, until they settled out and smothered the filter-feeding reef animals.
Ask the group what was worth quarrying from this area? Limestone. The “ballstones” were particularly pure forms of limestone.

Focus the group’s attention on the rock cycle, with particular emphasis on the carbonate cycle.

Suitable questions at this site Acceptable responses
Ask the group to identify the ways in which the limestone is being attacked by weathering? Biological weathering due to the effects of plant and tree growth.

Physical weathering due to frost action.

Chemical weathering by the effect of acidic rain.

What evidence can be seen for physical weathering of this face? There is a small scree at the foot, but it is grown over indicating it is not currently active.
What force brought the solid lumps of rock onto the scree? Gravity
What happens to the soluble products of chemical weathering? (e.g. breakdown products such as hydrogen carbonate and calcium ions). They will be removed in solution by groundwater
Assuming these ions are not precipitated, where will they end up? Springs will feed them into river flow and then to the sea.
Water will evaporate from the sea, but what will happen to the dissolved salts in the seawater? Eventually precipitated directly when evaporation is strong and circulation is weak, or used by animals to make shells.

When the animal dies what happens to the shell?

If these new limestones become buried how will they become exposed to weathering at the surface to start a new rock cycle?

Uplift by Plate Tectonic forces
Point out to the group that The Principle of Uniformitarianism suggests this same re-cycling happened to the calcite which now forms these limestone rocks. Ask how long is this last rock cycle, approximately?

[Emphasise the constant re-cycling of crustal material through geological time, via the rock cycle and that the evidence for several cycles are missing because of erosion]

At least 420 million years between chemical weathering of the ancient rock to form these limestones and the weathering today.


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