Wednesday 27 April 2011

‘Geology and Food – a Geologists Cookbook’

Geology and Food are two of my great interests, it seemed natural, therefore to tie them together within this blog, I have produced a series of recipes to fit within a geoscience outreach event (documented below) that are intended to explain the theory behind the geological principles. They are further fitted into the United Kingdom’s Key Stages, which dictate education – for more information please consult the earlier post.

The recipes described below:

Geological Idea
Concept, Key Stage and Area of study within National Curriculum,
Boiled Egg
Layers of Earth
Ks1-2 KS2 Sc4 Physical Processes> The Earth and beyond
Chocolate Brownies
Cumulate Textures
KS2 Sc3 Materials and their properties*> Separating mixtures of materials/ Changing materials
Flapjack and Slate
Slate Formation
KS2 Sc4 Physical processes> Forces and motion
Layered Cake
KS2 Sc4 Physical processes> Forces and motion & KS1 Sc4 Physical processes > Forces and motion
Jam Tarts
2 – Expansion 2 (KS2 Sc3 Materials and their properties*>Changing materials)
Crispy Jelly Sandwich
Crustal Rheology
 Sc3 Materials and their properties*
Lasagne Sheets 
Thrust Fault generation
KS2 Sc4 Physical processes> Forces and motion
Sugar crystallization
Mineral crystallization
KS2 Sc3 Materials and their properties*>Changing materials & KS1 Sc3 Materials and their properties > Changing materials
Making Chocolate Pillow Lavas
Pillow Lavas chilled margin
KS2 Sc3 Materials and their properties*>Changing materials
Expansion KS2 Sc3 Materials and their properties*>Changing materials & KS1 Sc3 Materials and their properties > Changing materials
Fizzy Drink
Gas Exsolution – felsic volcanism
Expansion KS2 Sc3 Materials and their properties*>Changing materials


Egg and Earth

What you will need
Free Range Egg

What to do:
 Bring a saucepan of water to the boil.
Add egg.
Leave for 5 minutes (need to ensure centre is fully cooked)
Remove from saucepan and allow to cool
Once cool, remove half the shell (in the event it falls off, retain shell)

Once the egg has been cut in half you should be able to see the layers of the egg. A simple comparison between the thickness of the layers of the earth and the layers of a chicken egg can be made. With a think outer shell, a thicker white (mantle) and a ‘core’ of yolk. The different makeup of all three layers is clear. This is very similar to the earth, where the mantle is made a set of minerals known as ‘peridotite’ while the core is made of Iron and Nickel - Just as within an egg the yolk is made of different material (more fat and protein within the yolk) compared to the white.   

Ultra Gooey Chocolate Brownie – Cumulate Textures
Makes 12

Before Cooking - the chocolate is evenly distributed
throughout the cake mixture

What you will need:
Plain chocolate
beaten (free range) eggs
Caster Sugar
1 teaspoon
Vanilla essence
Walnuts (or hazelnuts)
Plain white flour
½ level teaspoon
Baking powder
100g – 250g; works better with more
Milk chocolate bar or drops

Once cooked

What to do:
1> Grease an 18cm square tin
2> stand a large basin in hot water, put the margarine and plain chocolate within it, allowing to melt. Then cool
3> Stir in sugar, nuts, vanilla essence and eggs (I’d recommend in this order to stop over enthusiastic scrambled egg making), mix well, sift flour and baking powder – fold into mixture. Add chocolate drops
Aligning the cake slices one on top of each other gives
an example of the cumulate textures. 

4> pour into tin. Allow to sit for 5 minutes. Bake @ 180°C/350°F for 40 minutes. Then leave in tin to cool. Cut and enjoy!

Real world example of cumulate textures

While enjoying the brownie look into the slice can you see how the pieces of chocolate are at the bottom of the slab. If we imagine these represent minerals in a magma chamber that have crystallised first we can see that they have separated from the rest of the melt (or brownie mixture) and floated down to the bottom. While the nuts have crystallised last and are at the top of the magma chamber.  If you put slices on top of each other you can see a similar pattern to that observed in cumulate textures. 

Flapjack and Slate

In the pan

What you will need:
125g butter or margarine
100g dark brown soft sugar
3 tablespoons golden syrup
250g rolled oats
40g sultanas or raisins (optional)
What to do:
1.            Preheat the oven to 180 C / Gas mark 
Pushing down in the baking tray
2.            In a saucepan over low heat, combine the butter, brown sugar and golden syrup. Cook, stirring occasionally, until butter and sugar have melted. Stir in the oats and sultanas until coated. Pour into a baking tin – 30cm by 10cm works quite well. The mixture should be about 2 to 3cm thick – now push down really hard on the mixture, with washed hand – better still cover the flapjack with greaseproof paper/ clingfilm and place heavy objects over it while pushing down – the oats should all be lying flat. Flapjacks are notoriously good at getting stuck to whatever they are baked in so it’s a good idea to line the tray with either greaseproof paper or plenty of butter.

Once cooked
3.            Bake for 30 minutes in the preheated oven, or until the top is golden. Cut into squares, then leave to cool completely before removing from the tin. Enjoy! However, note how the oats are lying flat – like those in slate

view of flapjack slate (normal)
Slate is formed from individual minerals all facing the same way under intense pressure, the minerals are shaped like little plates, and oats provide a good comparison of this. We compress the flapjack (either in our hands or on the baking tray) to simulate the forces experienced by the slate during mountain building.  The non-squeezed flapjack shows the random and non ordered texture of– just like in a mudstone, where the minerals are all disorganised. We use slate in roofs because it splits into thin sheets – along lines of minerals. The minerals are much too small to see in slate but in this recipe, we can make a good comparison if we view a very zoomed up image of slate.
The small grains, if you look really carefully look a little bit like oats, which in our flapjack are closely forced together.

thin section image of slate - note similarities 

Angle Cake and Faulting

An unfaulted area of rock

What you will need: 
Either can be made or purchased (I bought it, however there are plenty of recipes for angle cake floating about). 
Stack three different cakes on top of earth other (ie chocolate, vanilla and choc chip... choices are yours!)

Normal fault exists when pieces of rocks are being pulled apart.
The block on the left has fallen – relative to the block on the right. 
This has allowed the cake to occupy more of the chopping board.
 If you get a stack of books and pull them apart, 
you will see many of these faults each pulled apart. 

A thrust fault exists when pieces of rocks are being pushed together,
 because the cake can’t be squashed – instead the block on the left has moved up
 against the block on the right – the cake now occupies less of the
What to do: Now get a knife and cut through all three stacked cakes at approx 40 degrees .

Faults exist because the rocks that make up the earth cannot take up all the movement between the plates by themselves, they bend and stretch, eventually a fracture develops and the two packages of rock are separated by what geologists call ‘faults’. Movement along the fault is often not smooth – because of bumps and grooves of the fault’s surface – eventually the pressure between the blocks is so intense that the fault suddenly gives way, slipping and generating an earthquake.

This cake represents a slice of an area of the earth’s crust. The layers in the cake are different beds of rock (and make it easier to see what is going on!)

Jam Tarts - Volcanoes 'Jamcanoes'

For the Pastry:

Flour (white or wholemeal)
½ level teaspoon
Butter or lard cut into 2cm2 cubes
2 tsp
Cold water

Equipment you'll need
What to do:
Mix flour and salt in a bowl, cut fat into small pieces then place into bowl and rub between fingers until mixture has a breadcrumb like consistency. Slowly add water and using a table knife stir until the mixture starts to bind. Then use your hands until you can form a ball. Alternatively if you have a food processor simply place ingredients in there in the respective order.
Ready to be cooked
Close up of eruption
On a clean, floured surface roll out the dough.  Cut the dough into circles that are twice the diameter of the tin you are going use.
Grease the tin and add the pastry circles. Add a tablespoon of jam to the pastry cases and fold the pastry over, push out air and seal with milk. Ensure that the jam is completely enclosed in the pastry.
Bake at 220°C/350°F for 20 minutes, or until golden brown. 

If you have an oven with a clear door you can see into watch the tarts as the jam warms, it will ‘erupt’ out of the pastry. Otherwise simply remove the tarts at the end of cooking, thy still continue to erupt. 

Once cooked - the jam is erupting out
As the temperature within the tart increases, this warms the water in the jam tart turns to steam, this increases the pressure within the tart, which traps some of the steam as bubbles within the jam.  Eventually the pressure within the pastry gets to high and the jam is forces out of the pastry cases to erupt out. This is a similar analogue to what occurs within a ‘real’ eruption where pressures within the magma are increased when it is heated.
The heat commonly comes from a fresh batch of magma from further down; obviously, this cannot be done with food so using an oven is as close as we can get! The sealing in of the jam within the pastry mimics magma being trapped within a volcano prior to eruption. Although, as the example above shows the seal is rarely perfect – this is a good analogue of how magma moves along faults in the crust to the surface... the jam has moved along faults in the pastry, under pressure, to leave the jam tart

Crispy Jelly Sandwich

Serves 1
What you will need:
Two slices of bread

What to do: Toast one of the slices of bread, spread jam on the untoasted slice and put the toasted slice on top.


the rheological differences are easy to see
This foodstuff is a good representation of the earth’s crust with a strong, but brittle and elastic layer (the toasted bread) sandwiched between a weak, ductile (can flow) layer with another strong elastic layer (the bottom bread) is a good analogy for the earth’s mantle and crust. But why do these layers form?
The crust we walk on is composed of different material to the mantle, further inside the earth. The material that makes up the crust is brittle (which is why we have earthquakes) but elastic enough to flow, so while the crust is a lot stronger and cooler than the mantle at the surface; as you go down in the crust it becomes warmer, this means that it is a bit molten (like a Slush Puppy) but still fairly solid – because of this it is weak, it can flow and move – like jam.  Once you move into the mantle, it is made of different materials, which are more solid than the overlying crust at high temperatures; this causes the upper mantle to be stronger than the lower crust, which is represented by the lower piece of bread. Under this model the plates move over the hard, dense mantle on a ductile layer - just like you can easily move the top slice of bread over the jam

Lasange Sheets and Thrust Faults

What to use: Ten or so sheets of lasagne sheets, if possible using green lasagne (Lasagne verdi) makes it easier to see how the folds change into faults
Bowl of water – to soak the sheets in.
What to do:
The images show that as force is applied from the left the sheets deform, first by moving up to accommodate the movement of my left hand right, then by folding, after extra pressure is applied the lasagne sheets cannot bend any further, this results in them behaving in a brittle manner – and snapping. The snapped sheets how form a small fault

The Sciency Bit:
Although we’ve only used a few sheets of lasagne to explain how folds can change into faults in the real world, it still provides a good example of how faults can develop. The lasagne can cope with a certain level of pressure – it does so by bending. Eventually it cannot take any more and snaps. This happens with rocks too, they respond a little like lasagne sheets, deforming until they snap and break apart. 

Sugar Crystallisation – Hot Vs. Slow 

NOTE: If being used for teaching this should be performed before the chocolate pillow lavas


Crystalline Sugar
What you will need: Saucepan/ non-stick frying pan and sugar (probably some decent washing up liquid too)
What to do: First the night before (or for as long as possible) put a plate or baking tray in the freezer. While you heat the sugar, place a plate or oven tray over a boiling pan of water
On the day, heat some sugar in a pan, over a medium-high and stir continuously until it is molten. It will darken significantly, but if it smokes, remove from the heat.
> Pour one third onto the baking tray/plate which has been in the freezer (or at least very cold)
> Pour another third onto a baking tray/plate at room temperature
starting to melt...
> And the final third can be poured to a baking tray which is over the pan of water – turn the gas/electric off immediately.  
Allow the sugar to set (obviously will take different times for each temperature of cooling)
Once the sugar has set, compare the three different trays/plates:
The sugar that was in on the coldest tray has the smallest (if any) crystals, while in the progressively warming trays the crystal size increases. The sugar can be eaten or dissolved in water to discuss dissolving
fully molten - ready to cool
Unfortunately, in the run I have done here the grain size difference was not large enough to be picked up by my camera – but using a hand lens I assure you it can be seen!

Sciency bit:
When the sugar is molten all the crystals have lost their shape, the molecules that make up the crystals are not in any real pattern or arrangement, as they have enough energy to not need to form bonds with each other. When you put the molten sugar onto a very cold surface suddenly the molecules have to try to make a pattern – but cannot because there is not enough time before they become cold enough to make bonds between themselves.
When the sugar has longer to cool down and make bonds between itself (at room temperature) some crystals can grow a little bigger, when the sugar has plenty of time to grow they can become big enough to see easily. This is what happens in igneous rocks – when magma cools down really quickly the molecules that make up the minerals do not have enough time to make organised bonds between each other – and have small minerals, when they have a longer time to bond together bigger minerals can grow.  

If the crystals are cooled very quickly (ie running under a cold tap) they form an analogue to volcanic glass. 

The change in colour of the sugar (from white) to toffee/brown can be used to discuss how rocks are melted to form magma (granite) different coloured sugars (muscovado, 
light/dark, granulated, icing etc)

Chocolate Pillow Lavas

What you will need: 60g of milk chocolate (pretty much any brand)
NOTE: If being taught it is recommended that, the sugar crystallization is done first.

Molten Chocolate

What to do:
Melt chocolate in a Bain Marie (bowl in hot water) until all molten, do not allow to ‘boil’ or burn.
Fill a bowl or jug with very cold water; but ensure that no ice is within it (although keep some nearby)

Using a spoon add the warm chocolate into the cool water, add ice afterwards to lower the water temperature further. Leave the chocolate ‘blob’ to cool until hard (dependent on size; takes about 5 minutes)

Adding the chocolate to very cold water
Remove chocolate pillow lava from the bowl and cut in half. Note the different size of crystals within the pillow basalt. Large crystals are in the middle, where the chocolate was warmest for longest, while the outside rim, that cooled quickly has a small grain size.  In comparison to ‘real world’ pillow basalts the differences in grain sizes is very subtle. In real world pillow lavas <<<< awesome video of pillow basalts off YouTube.>>>

Magma is forced into water – the magma is much hotter than the water (typically around 800°C)  so cools very quickly, this causes the crystals to form very quickly – as they have no time to grow. Crystals in the middle also cool down, but the rock which has already crystallised insulates them for a little while longer, which means that they grow bigger. 

Finished Product - note the grain size

 The Bag once shaken
Cornflakes & Liquefaction

What you will need: Cornflakes (still in bag)

First crunch up some of the flakes, then shake the bag of Cornflakes vigorously

Note how the larger flakes move to the top. The smaller flakes can fall between the larger ones as shaking continues.  Within sediments that have not yet become hard enough to be rock (for example in a river) soils are shaken by the seismic waves and smaller pieces of rock fall between the larger ones when sediments are shook.

This provides geologists with clear evidence that those sediments were changed by an earthquake event – which could happen again. This means that people can look back into the history of old earthquakes and try to predict how strong they were. 

The shaking in action

Fizzy drink Volcano

What you will need: Can of fizzy drink (shaken, not stirred)

What to do: Shake the can vigorously, then open it – stand away from anything that doesn’t need to get sticky. Observe how the drink gets sprayed out of the can very quickly.

Sciency bit:
When the can is shaken and then opened, the bubbles that were in the liquid suddenly expand, at a quicker rate than the liquid was leaving the can – this caused the gas to partially force the liquid out – spraying the drink everywhere. This is similar to what happens in a volcano; the gas dissolved in the magma (as it is so hot) suddenly bubbles out – creating an explosive eruption. In volcanoes that do not have a huge amount of dissolved gas in their magma (for example, Hawaii) the eruptions can be discussed using a non-fizzy drink (or partially), shaking it, and then opening it, the ‘eruption’ is much less exciting.

Note: this works best with small cans of fizzy sugary drinks (i.e. not alcohol) – the video is alcohol as we’d managed to drink / already sprayed the fizzy sweet drinks


Hopefully the recipes above have provided some food for geological thought – they are not designed to look like to rocks, but explain the theory and processes behind it, but more than that, the recipes are designed to be cooked, so please give them a go! Feel free to post comments, questions or successful attempts (or email me – top of the page), one quick thing though, I accept no responsibility for injury or illness caused through attempting to cook these foodstuffs . I hope that this is another way that geoscience can be communicated.

Happy Geology/Cooking!

Picture that caught my eye – bit of inspiration! 

From the Geological Society of London