# What is the Earth made of?
**URL:** https://boards.straightdope.com/t/what-is-the-earth-made-of/457155
**Category:** Factual Questions
**Created:** [July 20, 2008, 1:38pm UTC](https://boards.straightdope.com/t/what-is-the-earth-made-of/457155 "2008-07-20T13:38:41Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@Thinktank](https://boards.straightdope.com/u/Thinktank)
#### Post date: [July 20, 2008, 1:38pm UTC](https://boards.straightdope.com/t/what-is-the-earth-made-of/457155/1 "2008-07-20T13:38:41Z")
Actually now that I have your attention, more specifically:
What 1 rock/stone (that is in _solid_ form) is the Earth most composed of?
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### Author:  [@mks57](https://boards.straightdope.com/u/mks57)
#### Post date: [July 20, 2008, 1:50pm UTC](https://boards.straightdope.com/t/what-is-the-earth-made-of/457155/2 "2008-07-20T13:50:56Z")
Basalt.
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### Author:  [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)
#### Post date: [July 20, 2008, 3:04pm UTC](https://boards.straightdope.com/t/what-is-the-earth-made-of/457155/3 "2008-07-20T15:04:37Z")
Oxygen, silicon and [aluminum](http://en.wikipedia.org/wiki/Aluminum)
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### Author:  [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)
#### Post date: [July 20, 2008, 3:12pm UTC](https://boards.straightdope.com/t/what-is-the-earth-made-of/457155/4 "2008-07-20T15:12:49Z")
[QUOTE=WarmNPrickly]
Oxygen, silicon and [aluminum](http://en.wikipedia.org/wiki/Aluminum)
[/QUOTE]
Those are not rocks.
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### Author:  [@puppygod](https://boards.straightdope.com/u/puppygod)
#### Post date: [July 20, 2008, 3:32pm UTC](https://boards.straightdope.com/t/what-is-the-earth-made-of/457155/5 "2008-07-20T15:32:57Z")
Monocrystal iron?
Well, it’s one of the theories.
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### Author:  [@chrisk](https://boards.straightdope.com/u/chrisk)
#### Post date: [July 20, 2008, 3:44pm UTC](https://boards.straightdope.com/t/what-is-the-earth-made-of/457155/6 "2008-07-20T15:44:40Z")
A lot of the substances that make up most of the earth are probably not ‘rock’ or ‘stone’ in the traditional sense, if you consider the interior as well as the relative surface. Then again, a lot of that is indeed guesswork, because we can’t go and test substances at the center of the earth.
This link, especially the ‘chemical composition’ section, seems to have some useful and authoritative-sounding info: [http://www.austmus.gov.au/geoscience/earth/structure.htm](http://www.austmus.gov.au/geoscience/earth/structure.htm)
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### Author:  [@Derleth](https://boards.straightdope.com/u/Derleth)
#### Post date: [July 20, 2008, 4:39pm UTC](https://boards.straightdope.com/t/what-is-the-earth-made-of/457155/7 "2008-07-20T16:39:14Z")
Is silicon definitively out of the running? I thought most of the solid crust was silicon, but I guess most of it is broken up and mixed with other stuff.
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### Author:  [@Apex\_Rogers](https://boards.straightdope.com/u/Apex_Rogers)
#### Post date: [July 20, 2008, 6:58pm UTC](https://boards.straightdope.com/t/what-is-the-earth-made-of/457155/8 "2008-07-20T18:58:27Z")
[QUOTE=Derleth]
Is silicon definitively out of the running? I thought most of the solid crust was silicon, but I guess most of it is broken up and mixed with other stuff.
[/QUOTE]
The crust makes up a minuscule portion of the earth’s volume, less than 1% according to Wikipedia.
> **[Crust (geology)](https://en.wikipedia.org/wiki/Crust_(geology))**
>
> In geology, the crust is the outermost solid shell of a planet, dwarf planet, or natural satellite. It is usually distinguished from the underlying mantle by its chemical makeup; however, in the case of icy satellites, it may be defined based on its phase (solid crust vs. liquid mantle).
> The crusts of Earth, Mercury, Venus, Mars, Io, the Moon and other planetary bodies formed via igneous processes and were later modified by erosion, impact cratering, volcanism, and sedimentation.
> Most terrest...
I think a more likely place to look is the mantle, which Wikipedia describes as containing around 70% of the earth’s volume. Someone more knowledgeable than I with chemical structures and geology can parse through and determine which item that qualifies is most prevalent.
> **[Mantle (geology)](https://en.wikipedia.org/wiki/Mantle_(geology))**
>
> A mantle is a layer inside a planetary body bounded below by a core and above by a crust. Mantles are made of rock or ices, and are generally the largest and most massive layer of the planetary body. Mantles are characteristic of planetary bodies that have undergone differentiation by density. All terrestrial planets (including Earth), half of the giant planets, specifically ice giants, a number of asteroids, and some planetary moons have mantles.
> The Earth's mantle is a layer of silicate rock...
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### Author:  [@TheLoadedDog](https://boards.straightdope.com/u/TheLoadedDog)
#### Post date: [July 20, 2008, 7:33pm UTC](https://boards.straightdope.com/t/what-is-the-earth-made-of/457155/9 "2008-07-20T19:33:32Z")
> **[Mantle (geology)](https://en.wikipedia.org/wiki/Mantle_(geology))**
>
> A mantle is a layer inside a planetary body bounded below by a core and above by a crust. Mantles are made of rock or ices, and are generally the largest and most massive layer of the planetary body. Mantles are characteristic of planetary bodies that have undergone differentiation by density. All terrestrial planets (including Earth), a number of asteroids, and some planetary moons have mantles.
> The Earth's mantle is a layer of silicate rock between the crust and the outer core. Its mass of 4...
(fixed link)
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### Author:  [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)
#### Post date: [July 20, 2008, 7:44pm UTC](https://boards.straightdope.com/t/what-is-the-earth-made-of/457155/10 "2008-07-20T19:44:34Z")
[QUOTE=TheLoadedDog]
> **[Mantle (geology)](https://en.wikipedia.org/wiki/Mantle_(geology))**
>
> A mantle is a layer inside a planetary body bounded below by a core and above by a crust. Mantles are made of rock or ices, and are generally the largest and most massive layer of the planetary body. Mantles are characteristic of planetary bodies that have undergone differentiation by density. All terrestrial planets (including Earth), half of the giant planets, specifically ice giants, a number of asteroids, and some planetary moons have mantles.
> The Earth's mantle is a layer of silicate rock...
(fixed link)
[/QUOTE]
That’s what you think.
[Actually fixed link.](http://en.wikipedia.org/wiki/Mantle_(geology))
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### Author:  [@exastris](https://boards.straightdope.com/u/exastris)
#### Post date: [July 20, 2008, 10:48pm UTC](https://boards.straightdope.com/t/what-is-the-earth-made-of/457155/11 "2008-07-20T22:48:48Z")
I was thinking [peridotite](http://en.wikipedia.org/wiki/Peridotite), though wiki says it’s the most common in the upper mantle. Not sure if that’s because the lower mantle is a mixture that can’t really be discussed as “rocks,” or if there’s another more common composition to that portion.
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### Author:  [@Gus\_Handsome](https://boards.straightdope.com/u/Gus_Handsome)
#### Post date: [July 20, 2008, 11:17pm UTC](https://boards.straightdope.com/t/what-is-the-earth-made-of/457155/12 "2008-07-20T23:17:10Z")
I’m going with Carl Sagan’s answer:
Starstuff.
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### Author:  [@Great\_Dave](https://boards.straightdope.com/u/Great_Dave)
#### Post date: [July 21, 2008, 1:11am UTC](https://boards.straightdope.com/t/what-is-the-earth-made-of/457155/13 "2008-07-21T01:11:00Z")
[QUOTE=Q.E.D.]
> [@WarmNPrickly](#):
>
> Oxygen, silicon and aluminum
Those are not rocks.
[/QUOTE]
Good point. But those elements (really just Si and O) do combine to make most of the non-core earth. The problem with geology is that it is too complicated to speak in such simple terms as “What 1 rock/stone (that is in solid form) is the Earth most composed of?” We’ve only gone what, 10 kilometers in? Seismic studies and analysis of magma gives us a slim glimpse at what is going on below the Moho.
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### Author:  [@Fubaya](https://boards.straightdope.com/u/Fubaya)
#### Post date: [July 21, 2008, 3:00am UTC](https://boards.straightdope.com/t/what-is-the-earth-made-of/457155/14 "2008-07-21T03:00:40Z")
The question needs to be more specific. Basalt covers all the ocean’s floor’s which is 2/3 of the earth’s surface, so most people say it is the most common rock in the earth’s crust.
But on the continents, sedimentary rock cover 3/4 of dry land. Shale is the most common.
Deeper into the earth gets complicated. You’re getting into the rock cycle, where rocks can change form and rocks aren’t really named until they reach the surface anyway. But, just for the fun of it… the lower mantle is the deepest section of the mantle. I’m not sure if it has the most volume, but I assume it does. It’s solid rock and believed to be composed primarily of the minerals aluminous silicate perovskite. That could make it the most common rock on earth, although it isn’t really a named rock. I doubt that’s the answer the OP is looking for.
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### Author:  [@MrDibble](https://boards.straightdope.com/u/MrDibble)
#### Post date: [July 21, 2008, 2:02pm UTC](https://boards.straightdope.com/t/what-is-the-earth-made-of/457155/15 "2008-07-21T14:02:42Z")
Something in the peridotite range compositionally, but with elements of eclogite and other ultramafics. Something with olivine, pyroxene, garnets, spinels…diamonds! OK, maybe no diamonds.
At a really, _really_ rough first approximation, **garnet [lherzolite](http://en.wikipedia.org/wiki/Lherzolite)** is a best fit for the _ **rock** _ most common in the “solid” Earth (since the lower mantle is more plastic than solid). If I were to pick a single _ **mineral** _ (and the OP’s usage of the decidedly unprecise term stone makes me uncertain if it’s rock or mineral s/he wants here), it’d be [forsterite](http://en.wikipedia.org/wiki/Forsterite), [olivine](http://en.wikipedia.org/wiki/Olivine), although its wadsleyite and ringwoodite polymorphs may be more common _en masse_. Or perovskite polymorphs thereof, haven’t really looked into it. I’m going by my cursory knowledge of kimberlite xenoliths and greenstone belt genesis here.
The core, of course, is a Fe/Ni ball bearing. But only in the middle.
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### Author:  [@Thinktank](https://boards.straightdope.com/u/Thinktank)
#### Post date: [July 21, 2008, 9:59pm UTC](https://boards.straightdope.com/t/what-is-the-earth-made-of/457155/16 "2008-07-21T21:59:11Z")
Well folks to be honest I really didn’t think the question would make so much trouble for yous guys.
Like with Fubaya for instance, on one part of the Earth 1 kinda stone is the most common and another part something else is more common- but really doesn’t it just come down to what is bigger/denser? I’m not interested in what we don’t know folks, I’m interested in “thus far”.
I don’t really care if it’s a gem or a mineral, a stone, a plate or whatever else is a category.
And really the question was more in tune to the words " What 1 solid (fill in the blank)is the Earth _most composed of_?"
Basically, based on what knowledge we have of the density of the layers of the Earth, common sense would tell me to pick the densest solid layer of the Earth and try and figure out what the most plentiful, nameable, solid form exists there. That in my mind would be the (at least for our current knowledge) rock or stone that the Earth is composed most of.
If my tone sounds incorrect any, please forgive it. It was only through the many submissions here that I was able to narrow the choices down to some kind of volcanic rock or peridot… much stranger results than I was originally thinking.
I have to be so vague so that my use for this knowledge doesn’t influence the replies.
But basically anything goes as long as it’s a solid of some kind that the Earth is made of.
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### Author:  [@MrDibble](https://boards.straightdope.com/u/MrDibble)
#### Post date: [July 22, 2008, 1:58pm UTC](https://boards.straightdope.com/t/what-is-the-earth-made-of/457155/17 "2008-07-22T13:58:54Z")
Density’s got nothing to do with it - it comes down to volume. I’ll stick with olivine for an answer, closely followed by enstatite pyroxene.
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### Author:  [@septimus](https://boards.straightdope.com/u/septimus)
#### Post date: [June 14, 2014, 1:14pm UTC](https://boards.straightdope.com/t/what-is-the-earth-made-of/457155/18 "2014-06-14T13:14:52Z")
> [@MrDibble](#):
>
> Something in the peridotite range compositionally, but with elements of eclogite and other ultramafics. Something with olivine, pyroxene, garnets, spinels…diamonds! OK, maybe no diamonds.
>
> At a really, _really_ rough first approximation, **garnet [lherzolite](http://en.wikipedia.org/wiki/Lherzolite)** is a best fit for the _ **rock** _ most common in the “solid” Earth (since the lower mantle is more plastic than solid). If I were to pick a single _ **mineral** _ (and the OP’s usage of the decidedly unprecise term stone makes me uncertain if it’s rock or mineral s/he wants here), it’d be [forsterite](http://en.wikipedia.org/wiki/Forsterite), [olivine](http://en.wikipedia.org/wiki/Olivine), although its wadsleyite and ringwoodite polymorphs may be more common _en masse_. Or perovskite polymorphs thereof, haven’t really looked into it. I’m going by my cursory knowledge of kimberlite xenoliths and greenstone belt genesis here.
>
> The core, of course, is a Fe/Ni ball bearing. But only in the middle.
Ringwoodite is back in the news. [“Earth may have underground ocean three times that on surface”](http://www.theguardian.com/science/2014/jun/13/earth-may-have-underground-ocean-three-times-that-on-surface); this link links to a pay-to-view _Science_ article.
(Should I have resurrected this zombie, started a new Mundane-Pointless thread, or just abstained altogether?)
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### Author:  [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)
#### Post date: [June 14, 2014, 2:53pm UTC](https://boards.straightdope.com/t/what-is-the-earth-made-of/457155/19 "2014-06-14T14:53:04Z")
[Another article, not behind pay wall](http://phys.org/news/2014-06-evidence-oceans-deep-earth.html).
You can’t think of this water as a liquid, though. It’s a form of bonded hydrogen and oxygen atoms.
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### Author:  [@susan](https://boards.straightdope.com/u/susan)
#### Post date: [June 14, 2014, 6:01pm UTC](https://boards.straightdope.com/t/what-is-the-earth-made-of/457155/20 "2014-06-14T18:01:35Z")
> [@](#):
>
> (Should I have resurrected this zombie, started a new Mundane-Pointless thread, or just abstained altogether?)
In geological time, it’s not dead yet.
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