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What is the composition of the Earth's surface?
Question Date: 2020-03-12
Answer 1:

The composition of the Earth varies from place to place. The average composition of the Earth crust is about 60% Silica about 10 % alumina and the rest is CaO, FeO, MgO, Na2O and K2O.

70% in ocean basins is basaltic in composition; 30 % on continents is granitic in composition. You can look these up to get the oxide composition. When this is averaged you get an ANDESITE bulk composition.

Answer 2:

There are 8 major elements that make up the Earth's crust: O, Si, Al, Fe, Ca, N, K, and Mg (see graphic below). There are also a LOT of other what we call 'trace elements' that make up just a TEENSY bit of the Earth's crust (like 1.5%).


Answer 3:

The wording of this is ambiguous, with a couple of possible meanings. Using the interpretation of surface as being more or less "what can be seen from space", roughly 70% of Earth's surface is oceans while essentially all of the remaining 30% is exposed crust. Considering instead that the surface is the entire outer layer, or crust, of Earth (extending to a depth of ~70 km), the chemical species may be of more interest. The oceans are nearly all water (H2O), while the crust comprises various types of rocks and minerals. The most prevalent elements in these are oxygen (46.60% of the crust by weight fraction of the elements), silicon (27.72 wt%), aluminum (8.13 wt%), iron (5.00 wt%), calcium (3.63 wt%), sodium (2.83 wt%), potassium (2.59 wt%), and magnesium (2.09 wt%). About 92% of the crust consists of various silicate minerals (i.e., minerals containing silicon, oxygen, and possibly some other elements).

Answer 4:

Continental crust is predominantly granite, and oceanic crust is mainly basalt and gabbro. These are the main rocks, and the minerals that they are made out of are mostly silicates, especially feldspars.

Silicate minerals are based on groups of one silicon atom and four oxygen atoms. Because of this, even though the crust is made out of rock, the most abundant element is oxygen!

Answer 5:

Earth's surface is made of a lot of things: rocks, dirt, ice, ocean, and, in places, even human-made materials such as concrete and steel.

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