What is the Earth's composition (by compounds not elements)?

[James Nelson]

I have tried looking for papers on the composition of earth, but none of them seem to list the abundance of compounds. They just list the elements. So, what are the abundances of the most common compounds, by mass and/or percent of Earth?

 

[mfb]

As the mantle has 2/3 of the mass: Googling "earth mantle chemical composition" gives this article which summarizes several estimates of the chemical composition of the mantle on page 3. The outer core is liquid and doesn't have well-defined molecules, and the inner core should be more like a massive alloy where the concept doesn't make sense either. The crust is complicated, but I guess the main components can be found in some publications as well.

 

[Borek]

As mfb wrote - the main problem is that in many places it is hard to speak about "compounds". Many minerals are what we call a solid solution - mixture of several compounds forming a continuous solid (one that doesn't have to have a uniform composition!). Most rocks in the crust and mantle are composed mainly of silicates and if anything, I would assume silicates are the most common "compounds".

 

[Kevin McHugh]

Since the planet is c.a. 3/4 ocean, I think it is safe to say dihyrogen monoxide is one of the more plentiful compounds.

 

[Borek]

Since the planet is c.a. 3/4 ocean

Definitely not.

I think it is safe to say dihyrogen monoxide is one of the more plentiful compounds.

Definitely not.

 

[phyzguy]

Seconding Borek's "definitely not". The oceans are a very thin skin on the surface of the Earth.

 

[mfb]

To add numbers: As 0.45 of the mantle is SiO₂ and the mantle is 2/3 of the mass of Earth, 30% of the total mass is SiO₂ in the mantle (there is also SiO₂ in the crust). The whole crust has 0.5% of the mass of Earth, and the mass of the oceans is just 0.025% of the total mass of Earth.

SiO₂ beats H₂O by a factor of 1000.

 

[TeethWhitener]

SiO2 beats H2O by a factor of 1000.

This ignores the possibility of hydrated minerals in the mantle:

http://www.nature.com/nature/journal/v507/n7491/full/nature13080.html
http://www.nature.com/nature/journal/v507/n7491/full/nature13080.html
At least as far as I'm aware, we really have a terrible handle on how wet the mantle actually is.

 

[mfb]

Forgot "in the oceans" in my comment.

SiO₂ in the mantle beats H₂O in the oceans by a factor of 1000.

 

[ProfuselyQuarky]

Shouldn't the Earth's atmosphere be considered as well? I'm not saying that the percentage of compounds within the atmosphere would surpass that of the mantle and whatnot--I'm just asking whether the atmosphere should be considered as part of "Earth".

 

[Borek]

That's what I would do. Not that it will change things by much (perhaps for the noble gases?).

 

[mfb]

Looks like most of Earth's Argon atoms are gone in the atmosphere. A small contribution is in the crust (still about as much as tin and uranium, for example).

 

[Kevin McHugh]

Definitely not.
Definitely not.

My bad, I was thinking of the surface, not the whole planet.

 

[ProfuselyQuarky]

Looks like most of Earth's Argon atoms are gone in the atmosphere. A small contribution is in the crust (still about as much as tin and uranium, for example).

That's what I thought.

Edit: I hope that pun was intended.