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Plate Tectonics… A Spreading Zone… and a Slab of Chocolate

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Here is an explanation of how a plate tectonic spreading zone works…. using a slab of chocolate…. as you do…. and a bit of imagination.
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The choc' based explanation, may help visualise how the spreading process works and could help understand what can be seen on the geological map, shown below.


A brief on plate tectonics general
:
Plate tectonics is the name given to a process that takes place all over the Earth surface crust. The entire crust comprises, not one continuous crust, but a crust that has broken up into pieces (plates). Each plate is being shoved around by huge forces below it, from moving molten magma.
There are three main consequences that occur at plate edge zones / margins, depending on  the direction, relative to each other, that they are being shoved.
1. Both plate edges spread apart from each other (Spreading)
2. One plate edge is shoved under the edge of the other plate (Subduction)
3. Both plate edges collide and are often together, thrust upwards (Collision)


This article explains an example of 1. A Spreading Zone / Margin.
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This choc' based explanation below, should help understand what can be seen on the geological map, shown here:

Image depicting: Atlantic Ocean with Mid Atlantic Ridge (Spreading Zone) revealed

Image courtesy of The Open University**


Earth has a thin rock crust all over….. Made mainly of two sorts….. Continental Crust (the bit we jump around on and grey in the map picture)…. and Oceanic Crust (the bit that is between the chunks of Continental Crust and is red/yellow/green in the map pic).
This whole crust is broken in variously sized, solid pieces (plates)
 

There are many spreading zones between the plates and here we focus on one… The Atlantic Ocean Mid Atlantic Ridge.
You can learn how the spreading zone works, using a slab of chocolate and a bit of imagination:
Take slab of choc… this is your Continental Crust.
Before the Atlantic Ocean existed, South America used to be connected to Africa…. It used to be 'one land'…. as is our slab of choc.


You can demo how the 'one land', separated to form what is seen in the map, as it is today…. using the choc slab (plus imagination)

Place choc on table and snap it in two…. keep both bits together…. this represents the long ago 'one land'…. take a look at the map…. we will now create the Atlantic Ocean area and separate South America from Africa.


Look at your snapped choc slab…. imagine a flow of smooth melt choc comes out of the table below (all along the snap line)…. Then, as it flows up…. move the snapped choc slab slowly apart so the flow spreads thinly out on the table and you keep pulling the choc slabs further apart as the melt flows out…. STOP…. let melt choc 'sea floor' harden (all this held in your mind)
 

You should have:
1. A center line where the melt always flowed out from
2. An area of melt flow either side of the center line
3. Two slabs of choc, now separated by 1 & 2 above
 

That is what is seen on the map pic:
1 = spreading mid ocean ridge (redish line all up the mid ocean)
2 = Oceanic Crust (red yellow green areas, both sides of 1.)
3 = Continental Crust….. (grey chunks)
 

This shifting apart of the tectonic plates at a spreading zone, moves the 'choc slab' (Continental Crusts) apart…. causing continental drift. The melt choc is molten magma, pouring out, all along the center-line of the Mid Atlantic Ridge.
The Mid Atlantic Ridge is a huge long, still active volcano. This ridge is still spreading today. The Atlantic spreads further apart each year, by several centimeters
 

That's it….. You may now eat your chocolate.

** The Open University… Plate Tectonics Introduction (study course) S279… LINK HERE
** The Open University… Oceanography (study course) S330… LINK HERE



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The Author of this Post is Prof Puckit

Filed under: Earth and Oceanographic Processes · Tags: , , , ,

8 Responses to "Plate Tectonics… A Spreading Zone… and a Slab of Chocolate"

  1.  admin says:

    Use the tabs under the post – ‘Previous Post’ ‘Following Post’ – First Post’ ‘Latest Post’ – to move along the stories of Prof Puckit… in order of writing.
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    Use the CATEGORIES headings, in the top right column of page, to show all stories under the category.

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  2.  cwm says:

    Tested this post out a week or so ago, in a social media platform for education. It was adapted from it’s then, draft form, for explaining Continental Crust fragments in a spreading zone…. what they are.

    The explanation…. including use of chocolate…. was added as a comment to help explain Continental Drift in a speading zone.
    It included the choc slab concept and a bit of imagination….. as you do.

    Seems that the style proved out,… as helpful.
    Comment and Feedback on fb page “The Earth Story” — LINK HERE

  3. Elizabeth Aldrin Elizabeth Aldrin says:

    This is tremendous idea to explain the process. An established style to the Isostatic Changes article you have done..

    Superb for passing on educationally. Thankyou.

    I’ll get extra chocolate in case of severe “spreading”.

  4. Catherine Catherine says:

    Superb – This is another very clever style on imparting an understanding.

    I can use this as an education story for Earth Science.
    I can use this also, in modern day typical discussions, regarding climate change, as the Earth itself is still in flux – The chocolate is a fantastic idea for allowing a visual demonstration and will allow a greatly desired, very fresh angle, to be placed “in the mix”.

    More to follow? A series? I would hope.
    Very helpful. Amusing and very fresh thinking. Thankyou

  5. Mike Palmer Mike Palmer says:

    Saw you drop this onto Earth on facebook and noted it got top kudos award from their editor. Well deserving. Very nice style to put the oceanographic concept out to general public. Nice.
    Mike Palmer

  6. Bethany Harper Bethany Harper says:

    Love chocolate. Now I can eat during my lectures, as I describe the plates at the spreading axis.
    Excellent thinking on how to visualise this process. Thankyou

  7. Sam Sam says:

    Great article idea to put across in easy terms how some of the plate tectonics occurs. Subduction zones an hotspots are some more activities and would love you to cover those in your neat method of describing things. PLEASE :)

  8. Charlie Dean Charlie Dean says:

    Superb analogy. Well simplified for general public grasp / interest in the bit that gets taken for granted under our feet (and elsewhere).
    I can use this for Oceanography, Geography and Physics. I also know someone that will study this (practise studying this original concept) whenever they just fancy a munch of chocolate.
    Thanks

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