BOU/KS4/Prep

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Boulmer Foreshore, Northumberland

KEY STAGE 4 FIELD 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 4 Downloads
Homework Worksheets (pdf file, 73KB)
Group Leaders' Notes (pdf)

Many ideas involved in this Earth-Science On-Site excursion will revise ideas from Key Stage 3 work. See KS3 preparation.

At Key Stage 4, in addition to the knowledge and understanding of geological processes gained in Key Stage 3 Physics, the pupils’ knowledge of the response of materials to deforming forces, needs to be revised and slightly extended. See parts 1 and 2 below.

Contents

Introductory Work

In addition to the Key stage 3 concepts the following themes should form the basis of the preparatory lesson in school within a week prior to the field visit. The three themes are focused on understanding faulting, folding and igneous intrusion.

Part 1: The Response Of Materials To Bending Forces Time: (about 15 minutes)

In KS3, pupils are likely to have investigated the behaviour of springs and rubber bands when they are stretched. Under lower stresses, both show a linear relationship (known as Hooke’s law) between force (load) and extension. This is called elastic deformation. However as the stress increases, the behaviour of the two materials begins to differ; neither obeys Hooke‘s law any more, but the spring becomes permanently deformed, while the elastic band becomes much more difficult to stretch further, and eventually snaps, demonstrating brittle failure.

However, it is unlikely that pupils will have investigated behaviour of materials under bending forces. For the purpose of this preparatory lesson, a few quick qualitative demonstrations should be enough to achieve the following learning objectives:

  • know that under low bending forces, a strip of material will exhibit elastic deformation;
  • know that under higher bending forces, a strip of material will exhibit plastic deformation, becoming permanently bent;
  • know that under very high bending forces, a strip of material may snap, suffering brittlefracture;
  • know that some materials deform in these ways more readily than others.

For quick demonstrations the teacher will need to ‘sacrifice’ e.g. a few (old) wooden rulers (or wooden skewers), a few (old) plastic rulers (or similar plastic strips which do eventually show brittle fracture) and a few metal (steel) rulers (or similar metal strips which can be bent by hand). If a variety of metals in strip form such as copper, zinc, aluminium, are available for comparative purposes, so much the better. A steel wire coat hanger could be used to show brittle fracture after ‘working’ in the plastic stage.

Part 2: That Folds Are Formed Gradually, Under Compressive Stresses. (Time about 20 minutes)

The beds on the Boulmer foreshore are simply tilted to the SE, and may be regarded as one limb of a fold. The activity below is taken from the Earth Science Education Unit (ESEU) workshop “The Dynamic Rock Cycle”. Contact E SEU at www.earthscienceeducation.com for free materials relating to the teaching ideas of The Dynamic Rock Cycle. Contact eseu@keele.ac.uk for details of their facilitator scheme for free In-Service Training for science departments, funded by UK Oil and Gas.

Part 3. Make Your own Folds

Learning Objectives

  • Folds are caused by compression of rocks;
  • Folds are three dimensional, and form with their axes at right angles to the major stress;
  • Folds are evidence of ancient stress pattern in the Earth’s crust.

Equipment: a box with transparent sides (a chocolate box, or component drawer.) a spatula or desert spoon, a tray (to catch spilt sand) a cardboard paddle to fit snugly across the box, 500g of dry fine sand, 25g of flour, a photograph of folded rocks, digital camera (optional).

Teachers may want to do this as a demonstration, or, with multiple kits available teachers may want pupils to complete the exercise in small groups and discuss it afterwards to draw out the learning points.

Procedure: Place the cardboard paddle vertically at one end of the transparent box. Then build up several layers of sand and flour, but DO NOT fill the box more than half full. (It is useful to place the flour layer ONLY against the front face of the box, thus using less flour, and making the sand re-useable a second and third time.) (See Figure 1)

Very carefully, push the vertical paddle across the box, so that it begins to compress the layers. When you notice the layers beginning to bend, stop pushing. Hold the paddle upright and take a digital photograph, or draw a scaled diagram of the result.

BB10f1.jpg
Figure 1: Making Folds in Sand

Continue pushing the layers with the paddle until the sand is about to overflow the box. Hold the board upright and again photograph or draw a scaled diagram of the result. It should have features looking something like Figure 2. Photographs or sketches of the intermediate stages are also instructive.

BB10f2.jpg
Figure 2: Folds in Layers of Sand and Flour

The Discussion: Describe the folded nature of the layers, bringing out the following points;

  • The layers have been compressed into about 40% of their original length.
  • In order to do this they have deformed, or “folded” into upfolds and downfolds.
  • That this bending or “folding” happened over a period of time.
  • That the view is only of the end (or profile) of the fold, which actually runs all the way across the box, and formed at right angles to the main direction of compression.
  • Real folds in real rocks are therefore evidence of ancient compression directions in the Earth’s crust.

Then add arrows to your diagram (or printed digital photograph) to show the directions of the forces which were acting whilst you compressed the layers with the paddle.

Part 4. Igneous Processes

The central feature of this Earth Science On-Site visit is observation of igneous (dolerite) intrusions. The large dyke at Boulmer, (cutting across the bedding) requires some preliminary understanding of the geometry and origins of such features and their relationship to the bedding of the country rock they intrude.

Activities

Activity 1

Although videos and three-dimensional models are useful for establishing the main ideas and definitions, the ESEU workshop demonstration “A volcano in the laboratory” and the “Lava in the laboratory” pupil activity are extremely useful for demonstrating the processes involved, using red wax as a proxy for intrusive magma, and syrup as a proxy for extrusive lava. Details are available at: http://www.earthscienceeducation.com/workshops/rockcycle/volcano.htm

Activity 2

Pupils should examine and describe crystalline igneous rocks and relate the crystal size to rate of cooling, and the overall colour to acid or basic magmas. E.g. Granite, and rhyolite (both acid rocks), and basalt and dolerite (both basic rocks).

A summary of the central ideas and definitions is given below.

  1. Magma is liquid rock underground. (In this case it is iron and magnesium rich, or basic, magma which crystallised underground as the dark coloured rock dolerite).
  2. Basic magma derives from the partial melting of an otherwise solid upper mantle.
  3. Igneous rocks, therefore, are characterised by interlocking crystals and joints which form as the solid rock continues to cool and contract. In sheet shaped intrusions these joints are perpendicular to the cooling surfaces. As a crude rule of thumb, vertical joints in sills, and horizontal joints in dykes. In ideal circumstances the stresses form hexagonal columns.
  4. Hot magma moves upwards through cold “country rock” by virtue of being less dense. It follows lines of previous fractures such as faults and joints causing an extension of the crust equivalent to the width of the intrusion. Intrusions which cut across bedding in this way are called dykes. (At Boulmer the dyke is slightly over 30 metres wide.)
  5. Lava is the molten rock erupted on the surface, and cools quickly to form Basalt. Basalt is the fine grained extrusive equivalent of dolerite, which crystallises more slowly underground and therefore has slightly bigger interlocking crystals than basalt.
  6. Where the hydraulic pressure is insufficient to drive the intrusion further upwards through the country rock, the magma may spread out sideways, often along bedding surfaces, to form a sill. Here the ground’s surface is displaced upwards by the thickness of the intrusion
  7. Both sills and lavas can be parallel to the bedding, but the heat from sills, being intrusions, metamorphose the country rock both above and below. Lavas cannot do this.
  8. Dykes and sills effectively “cut across” the country rock and so are younger than them, (even if they occur above them in the quarry.) Principle of Cross-Cutting Relationships.

TEACHERS’ NOTE

It is only possible to get an absolute age in millions of years, for a geological event if it is possible to use radiometric dating techniques. The most usual form of dating for geological events is to establish a relative age: i.e. which order the events in a sequence occurred. Thus geologists use two concepts of time, an absolute time scale, and a relative time scale. Research is constantly attempting to improve accuracy of the absolute timescale, and the match between the two.

The fundamental geological principle is The Principle of Uniformitarianism: which states that the biological, physical and chemical processes we see today, operated in much the same way in the past, i.e. “The present is the key to the past”. In establishing the relative time scale the following six laws and principles are used:

  1. Law of Original Horizontality: All sedimentary rocks were originally laid down in a more or less horizontal attitude.
  2. Principle of Lateral Continuity: In principle, a sedimentary rock is laid down in a layer (or bed) that extends sideways (originally horizontally) and a bed may therefore be found in other places.
  3. Principle of Superposition: In any sequence of strata that has not been overturned the topmost layer is always the youngest and the lowermost layer the oldest.
  4. Principle of Faunal and Floral Succession: Fossil organisms have succeeded one another in a definite recognisable order over geological time. It follows that the same combinations of fossils in rocks have a similar (relative, not absolute) age, as do the rocks that contain them. This means that the relative age of sedimentary rocks may be identified by the fossils they contain.
  5. Principle of Cross-Cutting Relationships: Any structure (fold, fault, weathering surface, igneous rock intrusion, etc.) which cuts across or otherwise deforms strata must be younger than the rocks and structures it cuts across or deforms.
  6. Principle of Included Fragments: Particles are older than rock masses in which they are included. So the pebbles in a conglomerate are from rocks older than the conglomerate itself.

In-school learning in preparation for field visit to Boulmer Foreshore

List of the concepts needed

Sound knowledge and understanding of geological processes should form the basis of the preparatory lesson(s) at KS3 in school within the 1 to 2 weeks prior to the field visit.

KS3 geological processes Time: 80 minutes

In broad terms the KS3 ‘geological processes’ is the study of the ‘Rock Cycle’.

Learning objectives for KS3

  1. be able to describe and explain ways in which rocks are weathered.
  2. be able to observe and describe the key features of a rock specimen, including colour, texture and mineral content.
  3. be able to classify specimens of common rock types, using observed features, as igneous, sedimentary or metamorphic, and name such common rock types.
  4. be able to describe and explain how sedimentary rocks may be formed by processes including the erosion, transport and deposition of rock fragments.
  5. be able to make reasonable suggestions as to how a common sedimentary rock type they have described was formed, and how long the process took.

Objective A. Weathering (10 minutes)

As the basis of a brief question and answer session, use photographs of rocks that have suffered weathering. Suggested images:

  • boulder(s) showing onion-skin weathering
  • boulder(s) split in half – e.g. Devil’s Marbles
  • jagged, broken rocks on mountain ridges, preferably with patches of snow still visible.

An internet search yields many possible images for classroom use[1][2][3][4]

Some internet images provide useful background discussion about the weathering mechanisms involved. Tasks in small groups: show the pupils the photographs and give them one minute to come up with suggested causes of the weathering depicted in each image. There is probably no single ‘correct’ answer in any of these situations because weathering is rarely one process operating on its own. Weathering is usually caused by a combination of physical and chemical weathering processes. It is the pupils’ suggestions and subsequent discussion generated that are important. If pupils do not suggest chemical weathering, the teacher may need to pump-prime the discussion by asking them whether chemical changes might be possible in any of these examples.

Objective B. The rock cycle (35 minutes)

This session is based on the rock cycle. A simplified pictorial version of the rock cycle should be used in the session and this diagram can be downloaded[5]

Animations under the heading “The formation of fundamental rock types” are useful resources[6]

Activity 1

Provide a set of six common rock types (sandstone, shale, conglomerate, granite, dolerite/basalt with crystals just visible, slate or schist or gneiss). Tasks in small groups:

  • agree key features of each specimen (colour, texture, etc.), and whether sedimentary, igneous or metamorphic
  • provide a set of name labels; groups have to decide quickly which label belongs to each specimen, and be able to justify (for able groups, provide more name labels than specimens!)
  • plenary agreement on correct labelling and why the name label is appropriate.
Activity 2

Teacher shows quick demonstrations of:

  1. sedimentation jar filled with water then 3 charges of different sediment (the last one being muddy to show slow fall of sediment)
  2. a volcano in a laboratory. This demonstration of a volcano uses wax and sand. Details are available from Earth Science Education Unit[7]
  3. effects of pressure on rocks. This simulation of the distortion of fossils by metamorphism uses modelling clay and cockleshells. Details are available at Earth Science Education Unit[8]
    Task for small groups using the rock cycle diagram:
    • decide what part of the rock cycle each demonstration is modelling
    • decide at which point in the rock cycle each specimen would have been formed
    • agree on the rough timescale needed for each rock type to have been formed, including the difference, for sedimentary rocks, between time for deposition and time for a deposit of loose sediment to be turned into a hard rock, and also how that may happen.
Activity 3

How did sediment become hard rock? This can be modelled for sandstone, as shown on the Joint Earth Science Education Initiative website[9]

Objective C. Sedimentary processes (35 minutes)

Introduction

The following ideas are used in the field:

  • rock fragments are abraded (have pieces broken off) during transport;
  • erosion and deposition happens according to the size (weight)of the fragment in a flowing current;
  • larger (heavier) fragments are usually moved by rolling along the bottom, which causes them to become rounded;
  • that rounding / angularity refers to the sharpness of the edges of pebbles and can be described on a progressive scale. (Here the scale is of 1 to 6);
  • that well rounded pebbles are characteristic of significant amounts of transport by water. (Sand grains do not become well rounded during water transport);
  • that sediments become deposited together roughly according to grain size (mass) as a current slows down: larger fragments (sand and gravel) first and finer ones (muds) settling out in very quiet water.
MOS4f5.jpg
Figure 1: Rounded and angular edges
Activity 4

The following diagram could be used in conjunction with appropriately selected specimen pebbles to practice the description of rounding.

MOS6f2.jpg
Figure 2: Rounded and angular pebbles
Activity 5[10]

Pupils place cubes of sugar in a closed container and shake for 30 seconds and then observe changes to the shape and size of the cubes. Repeat activity at 30 second intervals, weighing & measuring the cubes at each stage. Tasks in small groups:

  • decide what is the cause of the changes they have observed.
  • decide what part of the rock cycle is modelled in the experiment.
  • agree what will affect the degree of rounding and size reduction of rock fragments in the rock cycle.
Activity 6[10]

Provide three piles of sediment (one of gravel, one of soil and one of sand) and watering cans for pupils to use to pour water over the sediments to see how far the water spreads the sediment. Tasks for pupils work in small groups:

  • agree what needs to be done to ensure the test will be a fair test.
  • pour 2 litres of water slowly over each pile of sediment.
  • observe what happens and measure how far the water spreads each pile.
  • agree which type of material was spread further.
  • predict what would happen if they poured 4 litres of water over each pile of sediment.
Activity 7

Teacher shows demonstrations of river erosion, transport and deposition using a child’s slide extension or a very long tray covered with a sand and gravel (pea-sized) mixture.

Tasks for pupils in small groups:

  • decide how the different types of sediment are moved along the river bed in this model.
  • agree where erosion takes place and what evidence shows that erosion has occurred here.
  • agree where deposition occurs and why deposition occurred at this place.
  • decide what different results they could expect to see if (a) the slope of the tray is increased and (b) a greater volume of water is poured into the tray.
Activity 8

Teacher shows a demonstration of the formation of ripple marks using a fish tank (approximately 100cm long, 50cm deep and 50cm wide) and two wooden cylinders 3cm diameter and slightly longer than the width of the tank.

Put clean, well sorted sand of fine to medium grain size into the tank, sufficient to line the floor of the tank to a depth of several cm. Place the tank on the wooden rollers, and fill the tank with water to a depth of 15-20cm. Gently and rhythmically rock the tank back-and-forth in an oscillatory motion until ripples form on the sediment surface. (This does not take long, but there is the potential for disaster if the tank is rocked too vigorously!).

D. Igneous Processes

The central feature of this Earth Science On-Site visit is observation of igneous (dolerite) intrusions. The large dyke at Boulmer, and the sills at Snableazes and Cullernose Point require some preliminary understanding of the geometry and origins of such features and their relationship to the bedding of the country rock they intrude.

Activities

Activity 1

Although videos and three-dimensional models are useful for establishing the main ideas and definitions, the ESEU workshop demonstration “A volcano in the laboratory”[11] and the “Lava in the laboratory” pupil activity are extremely useful for demonstrating the processes involved, using red wax as a proxy for intrusive magma, and syrup as a proxy for extrusive lava.

Activity 2

Pupils should examine and describe crystalline igneous rocks and relate the crystal size to rate of cooling, and the overall colour to acid or basic magmas. E.g. Granite, and rhyolite (both acid rocks), and basalt and dolerite (both basic rocks).

A summary of the central ideas and definitions is given below:

  1. Magma is liquid rock underground. (In this case it is iron and magnesium rich, or basic, magma which crystallised underground as the dark coloured rock, dolerite).
  2. Basic magma derives from the partial melting of an otherwise solid upper mantle.
  3. Igneous rocks are characterised by interlocking crystals and joints which form as the solid rock continues to cool and contract. In sheet-shaped intrusions these joints are perpendicular to the cooling surfaces. As a crude rule of thumb: vertical joints in sills and horizontal joints in dykes. In ideal circumstances the stresses form hexagonal columns.
  4. Hot magma moves upwards through cold “country rock” by virtue of being less dense than those rocks. It follows lines of previous fractures such as faults and joints causing an extension of the crust equivalent to the width of the intrusion. Intrusions which cut across bedding in this way are called dykes. (At Boulmer the dyke is around 30 metres across.)
  5. Lava is the molten rock erupted on the surface, and cools quickly to form Basalt. Basalt is the fine grained extrusive equivalent of dolerite, which crystallises more slowly underground and therefore has slightly bigger interlocking crystals.
  6. Where the hydraulic pressure is insufficient to drive the intrusion further upwards through the country rock, the magma may spread out sideways, often along bedding surfaces, to form a sill. Here the ground’s surface is displaced upwards by the thickness of the intrusion. (At Snableazes and Cullernose Point this is around 20 metres.)
  7. Both sills and lavas can be parallel to the bedding, but the heat from sills, being intrusions, metamorphose the country rock both beneath and above. Lavas extruded on the surface cannot do this. Sometimes sills “step across” bedding planes and continue at a higher, or lower, level. This is called a transgressive sill.
  8. Dykes and sills effectively “cut across” or metamorphose, the country rock and so are younger than them, (even if, as a sill, they occur above them in the quarry.) Principle of Cross-Cutting Relationships.

Objective E. Regional Metamorphism (caused by pressure and heat) (10 minutes)

Activity 9

This demonstration mimics new minerals forming at right angles to pressure in clay rocks, which causes it to split, or cleave, into flat pieces, as the sedimentary shale (or mudstone) becomes metamorphosed into slate.

MOS6f3.jpg
Figure 3: Cleavage and Folding
In rocks containing clay minerals the effect of severe folding can cause a cleavage (a new direction of splitting) to form. This occurs when new minerals that grow, do so at right angles to the direction of pressure. This means that such cleavage tends to run parallel to the axes of folds and cause the beds (now called metamorphic slates) to cleave across the bedding planes.

This can be simply modelled by using several randomly scattered pencils (or spaghetti pieces etc.) and confining them between two converging surfaces. For a whole group this is best done on an overhead projector screen. In practice these new minerals are flat, or platy, in shape, not elongate like pencils. (This effect can be modelled in the air with sheets of paper, illustrating the cleavage between the flat sheets, but this can be more tricky). This demonstration should be accompanied by specimens of slate showing cleavage.

MOS6f4a.jpg
MOS6f4b.jpg

Objective E. Contact Metamorphism (caused by heat)

Intruded hot molten magma loses heat to the surrounding rocks as it cools and crystallises. This baking of rocks is known as contact metamorphism. When clay-rich rocks are baked they re-crystallise and harden. Limestone recrystallises to form marble during metamorphism. Inspection of the properties of clay, limestone and marble before and after firing in a pottery kiln is instructive. At Snableazes close inspection of baked shales is possible.

An addition feature where igneous rocks cool more rapidly against the cold rocks they intrude is that grain sizes become finer towards the contact where cooling was faster. Investigations using salol on glass slides to demonstrate crystal formation and also the formation of igneous intrusive complex are part of the Earth Science Teachers Association workshop series[12]

Follow-up Work

The suggested follow up work is a summary of the evidence for the two rock cycles seen during the visit. A completed version allowing teachers to assess pupil responses can be found in Group Leader’s Notes.

As an alternative, the more graphical, last worksheet (worksheet 9) could be used instead. A completed copy of the follow-up work can be found in the Group Leader’s Notes.

Alternatively, the final exercise on local building stone could be used.

Building Stones Survey

Using the ideas from the preparation exercises pupils conduct a survey of the use of different building materials in the area of the school, using the worksheets at the end of this document.

After the Earth Science On-Site visit, as a homework exercise, pupils are asked to describe in detail two uses of stone as part of a survey of building stone in the local area.

The term “building” may need to be very loose. Suitable sites could include a local church, gravestones (helpfully dated), school buildings, local walls, high street shop fronts, kerbstones, cobblestones, local monuments, bridges, and the pupil’s own home. In particularly unhelpful areas concrete, cement and bricks could be designated as “man-made” stone for the purpose of this exercise.

Teachers (or pupils) should identify two sites to work on (perhaps taken from the preparatory homework exercise above). Remind pupils about situations where permission is required, and appropriate behaviour is expected. Also, draw attention to thoughts about safety, if kerbstones, or a cobbled road is chosen.

Pupils should record:

  • the location or address of the building / construction.
  • a sketch of the relevant part of the site, labelling the rock being surveyed, and the use to which it has been put.
  • A description of at least two different rocks (perhaps on two buildings) and the use to which they have been put. For each describe the rock, identify it as igneous, metamorphic, or sedimentary, and give the reason it has been used for this purpose.
  • Finally record the evidence for the effects of weathering on the chosen rock, identifying the kind of weathering responsible, giving the reasons for their conclusion.

References

  1. www.geos.ed.ac.uk/undergraduate/field/holyrood/spheroids.html
  2. academic.brooklyn.cuny.edu/geology/leveson/core/topics/weathering/picture_gallery/display/new_jersey_garret_mt_1.html
  3. www.au.au.com/cameras/images/devils-marbles.jpg
  4. www.thewalkzone.co.uk/Lake_District/walk_36/180203h.jpg
  5. The Rock Cycle www.washington.edu/uwired/outreach/teched/projects/web/rockteam/WebSite/rockcycle.htm.htm
  6. The formation of fundamental rock types available from earthsci.org/rockmin/rockmin.html
  7. A volcano in a laboratory www.earthscienceeducation.com/workshops/worksheet_index.htm
  8. The effects of pressure on rockswww.earthscienceeducation.com/workshops/rock_cycle/metamorphism.htm
  9. How did sediment become hard rock? www.chemsoc.org/networks/learnnet/jesei/sedimen/index.htm
  10. 10.0 10.1 Details of Activities 5 and 6 (and of related practical activities) are available at: [http://www.kented.org.uk/ngfl/subjects/geography/rivers/Teacher%20Plans/whatiserosionanddeposition.htm www.kented.org.uk/ngfl/subjects/geography/rivers/Teacher%20Plans/whatiserosionanddeposition.htm]
  11. A volcano in the laboratory http://www.earthscienceeducation.com/workshops/rockcycle/volcano.htm
  12. ESTA workshop series - Metamorphism www.earthscienceeducation.com/workshops/rockcycle/metamorphism.htm


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