2840: Earth Layers

Explain xkcd: It's 'cause you're dumb.
Jump to: navigation, search
Earth Layers
The Earth's magnetic field is primarily generated by currents in the liquid outer core, though some geophysicists argue that an unexplained mismatch with models suggests that the Kinder toy contains a magnet.
Title text: The Earth's magnetic field is primarily generated by currents in the liquid outer core, though some geophysicists argue that an unexplained mismatch with models suggests that the Kinder toy contains a magnet.


This comic reimagines the internal structure of the earth, mixing the real geological layers of the planet with fictional ones. Some of the fictional layers are appropriated from the layers of other objects that have cross-sectional diagrams, such as the layers of a piece of fruit, an eyeball, an item of confectionery or a building.

Layer Explanation
Lithosphere/Crust (50/50 Blend) A “50/50 blend” is a common description of clothing, such as a t-shirt made of equal parts cotton and polyester. Wearing multiple items of clothing over one another is commonly referred to as 'layering'.

The lithosphere is any outermost rocky layer of a planet. On Earth it consists of the crust and any parts of the upper mantle (see below) that do not convect. To say they are two distinct layers that could be blended together is rather nonsensical.

The upper limit of a planet's lithosphere is usually taken as where it meets the hydrosphere/atmosphere (wherever either may be present, otherwise the vacuum of space) but may or may not include the rock-derived pedosphere (for Earth, especially) or distinct overburden of loose regolith. All of these overlaid layers would typically be far too thin to be reliably distinct in the depiction of this Earth-like planet, and the diagram depicts the surface details only as a 'painted on' blue/greens/browns/etc to distinguish ocean areas and land heights with vertical depths/elevations that are already effectively insignificant at the scale of this diagram, before even considering the such relatively narrow layers of interface material.

Upper mantle An actual layer of the earth's structure.
Deep mantle A pseudo-correct layer of the earth's structure. There is a layer called the lower mantle, which could be what Randall refers to.
Filler This suggests there is space in the earth that was empty, so the creator(s) added some low-cost material which has the sole purpose of filling up the extra space.
Vitreous humor Vitreous humor (vitreous body) is the transparent gel inside the eye, located between the lens and the retina.
Mechanical/HVAC layer HVAC is an abbreviation for 'Heating, Ventilation and Air Conditioning' - the system used to heat or cool a building. Tall buildings may have a dedicated "HVAC floor" or "mechanical floor" between regular floors, like an extra layer.
Guacamole Guacamole is a dip or sauce made from avocados. Originating from ancient Mexico, it often includes onions, tomatoes and spices. Notably, guacamole is a major component of seven layer dip, and is shown here to be the seventh layer (from the surface).
Cytoplasm Cytoplasm is the "flesh" of both eukaryotic and prokaryotic cells; a jelly-like substance that fills all the otherwise empty space within the cell.
Cork Due to the proximity of the cork layer and the insulation layer, this may possibly be referencing cork-lined walls, which are used today mostly for high quality soundproofing, but have a considerable history. Another potential reference could be the fact that baseballs (another spherical shape) have a layer of cork in them (though it is usually in the center). Finally, the cork is a real layer of tissue in many woody plants, part of the bark. This comic was posted the day after Birkenstock Holding plc was listed on the New York Stock Exchange; Birkenstock sandals include a layer of cork.
Insulation Possibly a reference to the building insulation installed in the walls and ceilings of buildings. Technical fabrics used to make clothing also often include an insulation layer, combined with, for example, a waterproof/water-resistant membrane and an inner contact layer.
Seeds Part of a fruit which often appear in a distinct layer within, or sometimes on the surface of, the flesh.
Pith Part of a tree trunk or the thick spongy layer of the skin of a citrus fruit. Notably, this layer is below Seeds, which implies the seeds are outside of the pith. Although rare, some fruits do, in fact, have their seeds on the outside of their skin, such as Cashews. However, this is not present in any well-known citrus plants, or, if there are citrus plants like this, they are not discovered yet, let alone well-documented.
Nougat Nougat is a family of confections made with sugar or honey, roasted nuts, whipped egg whites and, sometimes, chopped candied fruit. It often appears as layers within confectionary items (such as Snickers, Double Decker and Mars) and, notably in relation to the comic, it constitutes the second-innermost layer of Mozartkugeln, a spherical confection.

Geography teachers sometimes hand confectionery like this to their students to give them an idea what "concentrically layered structure" means. Most of the time it turns out that this is their least concern, while at the same time a general consensus emerges that this is one of the best ideas said teacher has had in a long time. This layer is possibly an allusion to that practice.

Outer core An actual layer of the earth's structure.
Inner core An actual layer of the earth's structure.
Secret core Likely references secret compartments that may be hidden in the hardest to find recesses of other objects or structures, for the purposes of concealing precious items or closely-guarded secrets. Could also be interpreted as a section of the core that only certain people, such as Randall, are aware of. In the context of "inner core, outer core, secret core" may also be a riff on Leonard Cohen's Hallelujah, à la 2583: Chorded Keyboard.
Kinder toy capsule A Kinder toy is a reference to a chocolate egg-shaped confection by the Kinder brand, the Kinder Surprise, a chocolate shell with a plastic 'yolk' capsule in the center. Though that is loose within a void, unlike this 'Earth model', it closely matches this philosophy despite (or because of) being a banned food item in the United States, due to a 1938 FDA rule prohibiting a "non-nutritive object" (the plastic egg 'yolk' containing the toy) to be encased inside of an edible item (the outer chocolate layer) unless it has a specific function related to the edible part. It is widely believed that this is because the 'yolk' can be a choking hazard, despite the fact that you'd have to be swallowing a chicken egg-sized confectionery in a single mouthful for that to happen accidentally, or deliberately try to consume the plastic capsule whole. The toys within, however, may contain small pieces that can pose a choking hazard, especially in the toys that are packed as components, requiring some assembly, in order to fit into the capsule. Rules about small components (in toys for young children) and the inclusion of non-food contents within food-items have been used to prohibit this product within the US. To specifically overcome the latter regulations, the Kinder Joy was developed; an egg-shaped packaging containing the chocolate treat in one half and the toy separately within the other.

Randall's punchline of the comic is that there may indeed be a hidden toy at the center of the Earth.

The Title Text alludes to how kids like to guess what toy might be inside their Kinder treat. In this case, "some geophysicists" can do more than guess; they can infer that the Kinder toy core has a magnet (a popular type of toy) because it would explain a mysterious "mismatch" of current magnetohydrodynamic models not fully explaining observable phenomena. In this scenario, Earth's geomagnetic field is amusingly explained to be generated both by currents in the liquid outer core as well as the contents of the Kinder Toy Capsule core.

The text refers to a single Kinder toy, which is presumed to be huge, scaled to the size of the Earth's core, and to contain a proportionally-sized magnet.

As a thought experiment though, if we assume that the "Kinder Toy Capsule" actually contains multiple normal-sized Kinder Eggs, there would be approximately 50 sextillion of them. Here's the math:

  • The radius of the earth is 6371 km
  • If the diagram is to scale then measurement of it gives the Kinder Toy Capsule a radius of about 900 km.
  • This gives the Kinder Toy Capsule a volume of just over 3 billion km3.
  • Assuming a real Kinder Egg has a volume of 60 cm3, and a packing density of 63.5%, the Kinder Toy Capsule could contain 5×1022 (50 sextillion) actual Kinder Eggs.
  • (Current magnetohydrodynamics models of the Earth's core fail to contemplate the contribution of 50 sextillion Kinder Toy Capsules.)


The layers of the Earth
[Cutaway diagram of the Earth, a sphere with abstract sea/land/elevation surface, except for a slice removed (quarter-arc in three axes) to make visible a number of roughly equally-sized 'strata'/shells, all the way down to the intact smallest sphere. From surface downwards, these are:]
Lithosphere/crust (50/50 blend)
Upper mantle
Deep mantle
Vitreous humor
Mechanical/HVAC layer
Outer core
Inner core
Secret core
[The central sphere:]
Kinder toy capsule

comment.png add a comment! ⋅ comment.png add a topic (use sparingly)! ⋅ Icons-mini-action refresh blue.gif refresh comments!


Why are the seeds outside of the pith? Is there a fruit that is organized this way? SDSpivey (talk) 18:01, 11 October 2023 (UTC)

If there's one that's this way that contains pith, i can't find it, but raspberries, cashew apples, and blackberries all have their seeds on the outside SomeoneIGuess (talk) 20:09, 11 October 2023 (UTC)
The pith is the innermost part of a tree trunk. The part of a fruit is the pit, which is basically the same thing as a seed.-- 20:19, 11 October 2023 (UTC)
Ummm...the white, fibrous stuff within fruits that wraps around the seeds (like in oranges, for example) is called "pith", whether trees contain something by that name or not.Yorkshire Pudding (talk) 21:43, 11 October 2023 (UTC)
Strawberries are an (albeit rare) example of a fruit with the seeds on the outside of the pith (and skin, for that matter) 15:52, 12 October 2023 (UTC)
Actually, the white specks on strawberries that we commonly call seeds are achenes, which are actually individual, smaller fruits. It's the seeds within these achenes that are the actual strawberry seeds. SomeoneIGuess (talk) 20:43, 12 October 2023 (UTC)
Clear tootsie roll tootsie pop joke miss (awwaiid) 01:40, 12 October 2023 (UTC)

Something that seemed to be excessive to edit into the Explanation, but noting here in passing, the additional issue of magnets (in a Kinder context) is the problems of ingesting them. In addition to other issues, they can attract each other/separate bits of metal across folds of the digestive system and cause problems beyond merely their passage through the system (which they might not now be able to do). I don't even know if Kinder has ever included magnets, but I think they'd be extremely limited even outwith the US. (Though, as counter-example, there are Cow Magnets, designed for ingestion but not further digestion. And not for humans, nor the size of either a standard Kinder-yoke or a planetary one.) 08:50, 12 October 2023 (UTC)

When I saw guacamole in the comic, I assumed it was a reference to Apache Guacamole, as might be seen in a diagram of the different layers involved accessing some complicated computer system. Sandor (talk) 17:49, 12 October 2023 (UTC)

Some parts of the explanation, particularly the last paragraph, seem to assume that the diagram is supposed to be to scale. I don't think it is, since all the layers except the kinder toy capsule at the center are about the same size. Barmar (talk) 16:32, 13 October 2023 (UTC)

I've gone in and altered the last paragraph (it looks like the author of that wasn't too concerned about the near-similar thicknesses of the sliced-through strata, but I presume that it was a basic measurement and calculation of the relative radii of innermost and outermost spheres that came to the 900km conclusion). A very quick glance didn't suggest anything about the similar thicknesses in the list (may have missed it, it was a very very quick read-through!), but note that there is obvious variation, belying it being a "just line 'em up regularly" diagram but maybe just happens to be semi-accurately representing a semi-similar set of thicknesses. Because sometimes the things just turn out to be semi-regular like that, maybe? (Ok, so it's in a fiction/imagination, already, but if we're not allowed to be meta in xkcd then where else can one?) 20:36, 13 October 2023 (UTC)

> In the context of "inner core, outer core, secret core" may also be a riff on Leonard Cohen's Hallelujah, a la 2583: Chorded Keyboard. < ...How does this relate to the inner and outer core? Surely this should just say '"Secret core" may also be a riff on Leonard Cohen's hallelujah.'? 16:41, 14 October 2023 (UTC)