Geoscience, Stress and Chocolate

Royal Holloway logoHello, and I hope everything is well with you. This is my second blog. The first one had a broad introduction to the course and me. Thank you for those that responded to it. I hope the title of this blog has intrigued you to read more, and is with all things – it is not quite as you might originally think… One of the core components of this blog is geological stress, rather than any human, student or blogger stresses !

I want to try to achieve 3 things in this blog:
1. Give current or potential distance learning students some personal ideas, suggestions, advice and tactics on effectively studying remotely – that at least work for me
2. Give some practical, real-world examples and illustrations of the concepts I am being introduced to in my current module – Geological structural analysis, where I will expand on the title of this blog
3. Start to initiate and encourage some feedback, dialogue and possibly more of a discussion on the course I am on – with you – my unknown and disparate audience…

I have included some external website links and graphics to illustrate some of the information and points made here.

Topic number 1ideas, tactics and strategies for distance learning students

In some respects, this is such an individual topic – determined by people’s individual situation, circumstances, learning style. So, here is my personal perspective, which I have broken down into five main themes:

1. Most importantly, understand your own learning styles – how you really learn. For me, without getting into too much semantic discussion, I see a difference between developing understanding, and resorting to memory, for example, I have 2 traits:
a. I have a preference to start with the big picture, and fundamental concepts, so start from first principles, and what I know, or at least understand, and then work to the detail. If I don’t have these, I get bored, confused, and stuck very quickly.
b. I am very practical, so I want to know or understand real applications of the concepts and tools. I don’t like theory for theory’s sake. Application and utility is the key for me…
c. These ideas may or may not work for you based on your own personal learning style

2. If you are not enjoying, understanding, or learning from the course material, stop – re-think, come up with some similar terms, and look them up in Wikipedia. One observation about academics – they are so knowledgeable and expert about their specific fields, that they have forgotten what it is like to become familiar with the basics… So, you have to start from where you are at, which possibly means going outside of the materials they have provided. I believe there is a trend to use many terms/words for the same thing, which confuses the novice. My advice – start and try to keep things as simple as possible…

3. Time management – the usual, boring lesson for all students, but it is true: allocate, commit and stick to regular time slots. This is of course related to the element of personal discipline, which includes things like avoiding or minimising any distractions – TV, radio, phone, internet etc..

4. Find something of personal relevance and interest about the topic..

5. The other real challenge I have is actually committing the knowledge into my memory – which is kinda useful for the exams. One thing that works for me is just before going to sleep – reflecting on what I have learnt. The other benefit of this tactic is that it really does clarify what you thought you understood, but in reality – didn’t.

Topic number 2 – my current module – Geological structural analysis
My goal here is to try to give you some insight into the early content of this module. It is entitled Structural analysis and I am currently in week four of ten. This is broadly about the structural stresses and forces acting within the earth’s outer crust – and the impact on rock movements, and of course its relevance and application to finding and extracting oil and gas.

To illustrate the module content, I will discuss one concept from the module which is the strike-slip fault, and its relevance and application, particularly the forces, stresses and strains influencing the movement of such faults. An aspect of this is seismicity. Given the potential wide and varied readership of this blog I have to assume readers have a certain very basic knowledge of some core associated topics – plate tectonics, composition of the earth’s crust, forces, pressures, compression and expansion, stresses, fractures, brittle and elastic behaviour – with influence of temperature.

A short introduction can be found here.

Royal Holloway has a long history of experience in this field, and are recognised leading experts on structural geology. They have pioneered work on the modelling of structural geology by the use of initially quite simple but very powerful sand based models, and latterly with sophisticated computer modelling tools; and later in this blog I propose a much cheaper, nicer, but simpler modelling approach to the topic….

Of course, reality is very, very complex. To cope with this, from an understanding and learning, including an academic perspective, requires gross simplifications and generalisations. This blog is no different…

The first three dimensions….
Faults vary widely in size and scale, from very long, deep and wide zones like the Atlantic ‘spreading’ Mid Ocean Ridge or the San Andreas strike-slip fault in California, through to much smaller, short, shallow regional ones. But these are the fabric of understanding the range of stresses and their impact on the earth over geological time.

The fourth dimension…
Most maps portray the current situation/reality, at a moment in time. However, one of the key factors of geology is time – and there is lots of it. Billions of years and the impact of previous geological events shape and influence current structures, and can often be ‘re-activated’ e.g. previous faults from, say, a very old plate collision phase is a key factor.

If we focus not on hydrocarbon applications but on areas more relevant to the general public, then strike-slip faults are very important things, in large part due to the range of earthquakes associated with them. Examples are the San Andreas fault, and the terrible 2004 ‘Boxing Day Tsunami’ which initiated after rock movement around Sumatra.

A good reference website on these matters is provided by the BGS (British Geological Society) – link here: www.earthquakes.bgs.ac.uk, and of course Wikipedia.

I will start with the big picture and zoom in on one specific geographical area.

A continental view
I am sure whatever region you live or work, there are examples of earthquakes, small or large. However, I want to use the area around the UK as one geographical example. It is not known for its earthquakes, however there have been a few recent ones which have caught the UK news. At a continental perspective, the UK is part of the Euroasia tectonic plate, which, as its name suggests extends from the Atlantic MOR on the west and north – down to the Mediterranean sea to the south and east to China. So, the nearest major tectonic boundary to the UK is the Atlantic MOR – around 1,500 miles to the west and north of the UK – to Iceland. This MOR is pushing the Euroasia plate in a broadly south east direction. However this force is met with a corresponding force – from the south by the edge of the African continent tectonic plate. If we assume the African plate is not moving, then there are two opposing forces, resulting in compression – the UK is broadly being squeezed in a South-east / north-west axis. Although of course, when you get to more specifics, it is a little more complex than that…

A good diagram of the tectonic plates and at least their spreading rates, which is associated with the associated forces is below:

Tectonic plates boundaries

The country view
If we take the UK specifically – there are many different forces, stresses, strains and fault lines across the UK. Too many to mention – see Wiki page here.

A diagram of the stresses and strains in the UK as a whole is provided by the BGS (British Geological Society) – in its 2010 report.

Stress data for British IslesDon’t worry if you don’t understand the detail here. The main conclusion from this is that the size and direction of the stresses in the northern part of UK are very different to those in the south.

This is taken from an article written by Roger Musson in 1996 entitled, “The Seismicity of the British Isles”, for the Annali di Geofisica. This map shows the major structural divisions in the UK. This means the boundaries between the major tectonic ‘blocks’: A = Hebrides Microcraton, B = Metamorphic Caledonides, C = non-metamorphic Caledonides, D = Varescides, E = London Brabant Massif, F = North Sea Grabens. These do not equate strictly to fault lines.

One of the most intriguing and challenging aspects is that this needs to be viewed in 3 dimensions…

A region of the country view
Digging down a little deeper from this regional, macro scale view, I want to focus in one one particular area of the UK – that of the Bristol Estuary. On the 20th February 2014, around the area of the island of Lundy in the Bristol channel, there was a medium size (for the UK) earthquake measuring 4 on the ML (Richter Local Magnitude) scale. This was due to a very small strike-slip movement. Dr Ian G. Stimpson. Seismologist, geophysicist and structural geologist at Keele University has a very informative blog on this event.

The information from the BGS states that it was 5km (3 miles) down in the earth’s crust, and what I do know is that the continental crust is approximately 10km deep, and therefore this was a relatively shallow movement of rock.

This earthquake was the result of a force, pressure, stress build-up, and release in the local area, and the small resulting rock movement, or slip. This was a reflection of the regional/macro stresses/strains, and the very localised stresses and strains – in one particular area. The faults around the Bristol area have 2 specific orientations, some are north-east to south-west, and others are north-west to south-east, almost forming an ‘x’ shape. The reasons for these fault directions in this specific area go back to two large, and different mountain building periods many hundreds of millions of years ago (Caledonian and Variscan).

These periods of stress have caused significant fractures or crack in lower strata of rock. The complex fractures are illustrated below in the diagram. This is an extract from a 1989 paper from the Ussher Society Proceedings by R Gayer Department of Geology, University of Wales and J Jones of College of St. Paul and St. Mary, Cheltenham on The Variscan Foreland in South Wales.

diag 2Which exact piece of rock moved is as yet unclear… But you can begin to appreciate the complexities involved.

You can try this at home…
So, having gone through the preceding explanation, now we get to the really interesting part… this is where the chocolate comes in! There is a very wide range of chocolate confectionary and food, which can , interestingly enough demonstrate some of the structural geology concepts.

Kit KatTake a Kit-Kat…. This breaks easily into the bars at the relevant lines. This can be thought of as layers of rock underneath the earth’s surface. This is an example of brittle behaviour.

 

 

Mars BarThen take the example of a Mars Bar, or this has several layers – each with different properties –some easily flowing, some hard and brittle.

 

 

Twix fingersA good chocolate simulation of a Strike Slip fault can be achieved with a Twix bar – with the 2 fingers. Place these side by side and move them against each other – this is a great example of the friction and types of movement of such a boundary.

After Eight mint chocolatesAnother good chocolate analogy is After Eight Mints – with their hard outer layer, and soft center – they too can provide a good simulation of the various forces operating in the earth’s crust.

 

 

Liquorice_Allsorts[4]

Another simple illustration can be achieve using Liquorice Allsorts – where the three layered variety provide a great simulation for compressing, pulling and shearing of the earth’s layers.

Now that I have set your mind racing with such a metaphor – what other ideas do you have to use confectionary to simulate geological events and processes ? 

 

Topic number 3

I am new to blogging, I am still trying to work out how it works, what the engagement rules are, who reads this stuff, and why… So, all I am really saying is – give me feedback, what do you think of this, what would you like me to talk about… how can I improve ? What level of geological expertise are you ? Many thanks, stay safe, learn constantly, and have fun.

Pete

Pete is studying for the MSc Petroleum Geoscience by distance learning. He lives in the UK.

Leave a comment

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s