E is for earth

Brooke Wisdom

May 1, 2010

E is for Earth

The planet’s layers — particularly the earth’s crust — provide many of life’s essential building blocks.

By Bill Langer


‘The Earth is a great lump of dirt rolled up together, and … hanged in the Air.’ (Culpepper, 1658, Astrological Judgement [sic] of Diseases, p. 31).

Actually, the Earth is not quite that simple. Our planet is made up of three main layers — crust, mantle, and core. The crust is very thin compared with the mantle and core, and makes up less than 0.5 percent of the Earth’s mass. Crustal plates drift atop the soft, underlying mantle, and these plates are made of rocks and minerals that are the source of … well … practically everything we use.

Our homes contain concrete foundations made with limestone and aggregate; drywall made from gypsum; paint that contains titanium dioxide; window glass made from silica sand; electrical wiring and plumbing made from copper; sinks and toilets from ceramic clays; and stainless steel faucets and appliances made with iron, chromium, nickel, and molybdenum. All these mineral resources come from the Earth’s crust.

Plants ultimately get their nutrients from minerals in the crust. Humans enhance the growing process of plant crops by fertilizing fields with phosphate, potash, and lime. Food processors add a variety of minerals to their products including: calcium carbonate and sodium bicarbonate (leavening agents); calcium silicate and silicon dioxide (anti-caking agents); iron or ferrous sulfate (nutrients); sodium carbonate (an acidulant); and sodium chloride and sodium nitrate (a preservative). Diatomite and bentonite clay are used to clarify beer, fruit juices, and wine. Food and drink is packaged in cans made from aluminum or steel, in glass made from silica sand, or plastic packaging made from oil, natural gas, or coal. All those minerals come from the Earth’s crust, too.

Even the human body is dependent on elements that ultimately come from the crust. Carbon occurs throughout the body. Oxygen and hydrogen are found in all body fluids, tissues, bones, and proteins. Calcium and magnesium are in the lungs, kidney, liver, thyroid, brain, muscles, heart, and bones. Some elements occur in extremely small amounts. For example, cobalt (less than 0.00001 percent of the mass of the body) is a constituent of vitamin B12, which is important for metabolism, the formation of red blood cells, and maintenance of the central nervous system. Some trace elements do not yet have any identified biological role.

Our bodies obtain most of these essential minerals through the food we eat. However, some people take mineral supplements that often are products of mining the crust. Minerals that have been extracted from the earth’s crust for use as supplements are commonly sent to manufacturing laboratories. There, they go through a purification process and are combined with other ingredients to make them stable, non-toxic, and more absorbable.

A good example is Selenium, which is a byproduct of copper mining. When used as a mineral supplement, selenium is refined to sodium selenite or selenate. When marketed as an organic product, selenium is provided to yeast cultures where the yeast incorporates the selenium into its cells as an amino acid complex called selenomethionine. Selenium helps the pancreas and heart function properly, helps protect blood cells from certain damaging chemicals, and helps our immune system produce antibodies. Selenium is also needed to make our skin elastic.

And if our skin was not elastic, it would break apart into chunks like the plates that float around on the Earth’s crust. But that’s another story.

Bill Langer is a geologist with the Mineral Resources Team of the U.S. Geological Survey and can be reached at 303-236-1249 or via e-mail at blanger@usgs.gov.

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