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17

The only elements that were formed on Earth are those produced by radioactive decay. There are four natural decay chains that start with transuranic elements and none terminate in iron; neither do the decay chains that are artificial or those that result from cosmic radiation. So all of our iron is from the Earth's formation or meteor impacts since then.


11

I can only answer the question of why is it mostly iron. Not too sure of the magnetic properties of iron versus nickel. As said in another answer, there is simply much more iron around than nickel. But the earth has also a large amount of other metals: silicon, magnesium, calcium, aluminium. So why is the core made of iron-nickel and not the other stuff? ...


11

All the material that eventually formed our solar system is essentially recycled star dust. All iron on Earth was produced by large stars that existed before our Sun formed: the iron was created during nuclear fusion and later released when the parent star(s) exploded, presumably supernova. After our solar nebula had formed and material had been ...


10

A few elements to complement @Siv answer, and some alternatives hypotheses: Originally the idea was that the Fe2+ oxidation into Fe3+ that lead to the formation of the BIF ("banded iron formations") was an indirect consequence of the increased atmospheric pO2 caused by the photosynthetic activity of, then freshly appeared, cyanobacteria (see e. g. Cloud ...


7

Not all the iron sank to the core. Have a look at my answer to a previous question: https://earthscience.stackexchange.com/a/7076/725 Your question is similar, but coming the other way. You're asking - why is there iron in the mantle/crust? The answer is that there was enough oxygen left in the Earth after oxidising the other lithophile elements (Si, Mg, ...


6

The main reason that there is more iron than nickel in the Earth's core, and in the universe generally, is that Nickel-56 beta-decays to Iron-56 (via cobalt-56). Much nickel-56 forms in Asymptotic Giant Branch stars and supernovae. However, nickel-56 decays with a half-life of 6 days. In nuclear fusion in stars, He-4 nuclei (alpha particles) form ...


6

At μ/g level some decade ago, they were explained as forming in relation to the oxygenation of the atmosphere, as photosynthetic life developed changing a reducing environment to an oxygenated one, iron oxides formed precipitating out of seawater in variable bands related to local (or possibly seasonal) oxygen availability. Though this traditional ...


6

I believe the element iron (Fe) is formed by stellar nucleosynthesis. stellar nucleosynthesis: it's a process of continuous fusion of the star element to reach heavier and heavier elements. starting from hydrogen (H) till iron (Fe) (the heaviest element the process could reach). Each 2 atoms of light elements fuse together to form heavier element atom. ...


5

So (naturally occurring) elements on earth can only come to be here in three ways. Either they are formed here via radioactive decay. They came via meteor. They were already here. As mistermarko stated above iron isn't normally formed via radioactive decay, so we're left with the last two choices. However if we go back far enough, earth itself was a bunch ...


5

Somewhat more from volcanic activity than meteor impacts, but both are important. The Earth has an iron-nickel ($\ce{Fe}$-$\ce{Ni}$) core that originates from Earth's formation out of the collision of planetesimals which themselves contained iron, rock and ice. The Earth was very hot at that time, and the iron along with some siderophilic elements sunk to ...


3

tl;dr If it's red, it's iron. If it's soil, it probably has iron even if it's not red. Therefore there's no point testing it for iron (in a simple way), because you can be confident it's there. I'd like to add a bit to Jezibelle's answer. First of all, you could do a simple chemical test to test for iron, but that would not give you much. Iron oxides on ...


2

Soil redness is typically from hematite (an iron oxide). The mixture of other minerals and organic products and how well-drained the soil is determines the exact shade. You can buy soil test kits that include iron, or, alternatively, run some distilled water through a soil sample over a cheese cloth or two and use a water test kit on the filtrate (water ...


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