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Visualize the scale and composition of the earth’s crust
Ever since humans roamed the top of the earth’s crust, we’ve been fascinated by what’s inside.
And the makeup of the Earth has been vital to our advancement. From finding the right types of rocks to make tools, to building efficient batteries and circuit boards, we rely on minerals in the earth’s crust to fuel innovation and technology.
This animation by Dr. James O’Donoghue, planetary researcher at the Japan Aerospace Exploration Agency (JAXA) and NASA, is a visual comparison of the Earth’s outer layers and their major constituents in mass.
What is the composition of the earth’s crust?
The combined mass of surface water and the earth’s crust, the rigid outer layer of our planet, is less than half a percent of the total mass of the Earth.
There are over 90 elements found in the earth’s crust. But only a small handful make up the majority of the rocks, minerals, soil, and water we interact with on a daily basis.
Silicon dioxide (SiO2), found in pure form as the mineral quartz. We use quartz in the manufacture of glass, electronics and abrasives.
Why is silicon dioxide so abundant? It can easily be combined with other elements to form “silicates, “a group of minerals that make up more than 90% of the earth’s crust.
Clay is one of the most well-known silicates and micas are silicate minerals used in paints and cosmetics to make them shine and sparkle.
|Mineral||Major elements||Percentage of crust|
|Plagioclase feldspar||O, Si, Al, Ca, Na||39%|
|Alkaline feldspar||O, Si, Al, Na, K||12%|
|Pyroxene||O, Si, Mg, Fe||11%|
|amphibole||O, Si, Mg, Fe||5%|
|Micas||O, Si, Al, Mg, Fe, Ca, Na, K||5%|
|Clay minerals||O, Si, Al, Mg, Fe, Ca, Na, K||5%|
|Other silicates||Oh yes||3%|
2. Aluminum and calcium
SiO2 binds very easily with aluminum and calcium, our next most abundant constituents. With a little sodium and potassium, they form feldspar, a mineral that makes up 41% of rocks on the surface of the Earth.
Although you may not have heard of feldspar, you use it every day; it is an important ingredient in ceramics and it lowers the melting point of glass, making the production of screens, windows and glass cheaper and easier.
3. Iron and magnesium
Iron and magnesium each make up a little less than 5% of the mass of the crust, but they combine with SiO2 and other elements to form pyroxenes and amphiboles. These two important mineral groups make up about 16% of crustal rocks.
Perhaps the best known of these minerals are the two varieties of jade, jadeite (pyroxene) and nephrite (amphibole). Jade minerals have been valued for their beauty for centuries and are commonly used in countertops, construction, and landscaping.
Certain asbestos minerals, now widely banned for their carcinogenic properties, belong to the group of amphibole minerals. They were once in great demand for their insulating and flame retardant properties and were even used in brake pads, cigarette filters and as artificial snow.
Surprisingly, even though it covers nearly three-quarters of the Earth’s surface, water (H2O) compose Less than 5% of the mass of the crust. Part of the reason is that water is significantly less dense than the other constituents of the crust, which means it has less mass per volume.
Breaking down the earth’s crust by element
While there are many different components that make up the earth’s crust, all of the above include oxygen, among others.
When the crust is broken down by element, oxygen is indeed the most abundant element with just under half the mass of the earth’s crust. It is followed by silicon, aluminum, iron, calcium and sodium.
All the other remaining elements make up a little more than 5% of the mass of the crust. But this little section includes all metals and rare earth elements that we use in construction and technology, which is why discovering and extracting them economically is so crucial.
What is below?
As the crust is only the outermost layer of the Earth, there are other layers to contemplate and discover. Although we have never directly interacted with the Earth’s mantle or core, we do know enough about their structure and composition thanks to seismic tomography.
The upper mantle
AT some specific points on Earth, volcanic eruptions and earthquakes have been strong enough to expose pieces of the upper mantle, which are also mostly silicates.
The mineral olivine makes up about 55% of the composition of the upper mantle and causes its greenish color. Pyroxene comes in second with 35%, and calcium-rich feldspar and other calcium and aluminum silicates represent between 5 and 10%.
Go even further
Beyond the upper mantle, the makeup of the Earth is not as well known.
Deep mantle minerals have only been found on the Earth’s surface as components of alien meteorites and as part of diamonds high from the deep mantle.
One thing the lower mantle is believed to contain is the silicate mineral bridgmanite, at an abundance of up to 75%. The Earth’s core, meanwhile, is said to be made up of iron and nickel with small amounts of oxygen, silicon, and sulfur.
As technology improves, we will be able to discover more about the mineral and elemental makeup of the Earth and better understand the place we all call home.