Wut r the sim/diff between solar elemental abundance & that observed in meteorites? Wut r the major diff between the composition of the whole Earth & crust? Wut processes have given rise 2 these diff?

Question

For an earth and planetary science class. Geology focused.

Sim: Similarities

Diff: Differences

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Answer 1

Hi Maria! These are some pretty big questions, so let's break them down into a few major concepts. I'd be happy to discuss them more in depth during a session! Also keep in mind many of these questions are still debated and researched today.

What is similar and different between the elements found in meteorites and in the Sun?

1. For this question, it's important to realize there are multiple types of meteorites. The most important for answering your question (and possibly in all of geology) are chondrites or chondritic meteorites. They form from primitive solar system materials early in the formation of the solar system. They are the oldest materials scientists can study and they represent what is believed to be a "bulk composition" of sorts within the early solar system.
2. Regarding the Sun, it's important to think about the processes happening inside of the Sun that make it a star. These processes inform the chemical composition and are, broadly speaking, nuclear fusion and decay. One common process you may have heard of is proton-proton fusion, which turns two H atoms into He, gamma radiation, and neutrinos. The fusion of elements can happen to a greater and greater extent until you make molecules about the mass of Fe, at which point fusion is no longer a favorable mechanism of forming heavier elements within the Sun.

What is the difference between the composition of the Earth and the crust? What processes have given rise to these differences?

1. When the Earth initially formed, it is thought that it was, essentially, a molten ball of magma. This then differentiated and began to cool slightly. This process is what causes compositional differences between the layers of the Earth. Simply put, heavier elements went deeper into the Earth and lighter elements formed the crust. However, other important factors about the elements, such as ionic radii, charge, and oxidation state effect which minerals/layers/phases these elements went into during differentiation.