Visualize the scale and composition of the Earth’s crust
Ever since humans roam atop the earth’s crust, we’ve been fascinated by what’s inside.
And the composition of the Earth has been vital to our advancement. From finding the right types of rocks to make tools to making efficient batteries and circuit boards, we rely on the 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 by mass.
What is the composition of the earth’s crust?
The combined mass of surface water and the Earth’s crust, the outermost rigid 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.
Most abundant in the crust is 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 combine with other elements to form “silicates“, a group of minerals that make up over 90% of the earth’s crust.
Clay is one of the best known silicates and micas are silicate minerals used in paints and cosmetics to make them shine and sparkle.
|Mineral||Main elements||Crust percentage|
|plagioclase feldspar||O, Si, Al, Ca, Na||39%|
|alkali feldspar||O, Si, Al, Na, K||12%|
|Pyroxene||O, Si, Mg, Fe||11%|
|Amphibole||O, Si, Mg, Fe||5%|
|Mica||O, Si, Al, Mg, Fe, Ca, Na, K||5%|
|clay minerals||O, Si, Al, Mg, Fe, Ca, Na, K||5%|
2. Aluminum and calcium
SiO2 binds very easily to 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 Earth’s surface.
Although you may not have heard of feldspar, you use it every day; it is an important ingredient in ceramics and lowers the melting point of glass, making it cheaper and easier to produce screens, windows and drinking glasses.
3. Iron and Magnesium
Iron and magnesium each constitute just under 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 constitute 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.
Some 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, although it covers almost three quarters of the Earth’s surface, water (H2O) make up Less than 5% of the mass of the crust. This is partly because water is significantly less dense than other constituents of the crust, meaning it has less mass per volume.
Breaking the earth’s crust by element
Although there are many different components that make up the earth’s crust, all of the above elements include oxygen in particular.
When breaking down the crust 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 the metals and rare earth elements that we use in construction and technology, which is why their discovery and economic extraction are so crucial.
As the crust is only the outermost layer of the Earth, there are other layers to contemplate and discover. Although we have never interacted directly with the Earth’s mantle or core, we know quite a bit about their structure and composition thanks to seismic tomography.
The upper mantle
AT some specific spots on Earth, volcanic eruptions and earthquakes have been powerful enough to expose chunks of the upper mantle, which is also made mostly of 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 aluminum silicates make up between 5 and 10%.
Go even further
Beyond the upper mantle, the Earth’s composition is not as well known.
Deep mantle minerals have only been found on Earth’s surface as components of extraterrestrial meteorites and as part of diamonds upwelling of the deep mantle.
One thing the lower mantle is thought to contain is the silicate mineral brigmanite, at an abundance of up to 75%. The Earth’s core, on the other hand, would be composed 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 composition of the Earth and have a better understanding of the place we all call home.