Have You Ever Wondered Why the Blue Ridge Mountains Are Blue?

A natural phenomenon creates the blue haze that rests over the region.

The blue haze that rests over the Blue Ridge Mountains is a familiar sight experienced by travelers worldwide. A 1964 article from The New York Times paints the picture, "The Blue Ridge Mountains, which twist from Pennsylvania to Georgia with as many moods as the sea, display a wide variety of shades—all of them blue. Some summer days, the mountains are a powder blue that is almost gray. Other days, they are robin's egg blue, or they may be cerulean, turquoise, blue‐black, or purple." It describes the many ways—over many decades—scientists have tried to determine why the mountains appear blue.

As described by the National Parks Service, "The Blue Ridge province is a mountainous belt […] made of highly deformed metamorphic rocks of largely Precambrian ages. These include schists, gneisses, slates, and quartzites, and are extensively intruded by igneous bodies." The region is covered in many species of plants and is blanketed by thick forests, making it a very biologically diverse area. It's certainly a sight to see, but the region's telltale hue was a mystery for a long time.

Blue Ridge Mountains
Franz-Marc Frei/Getty Images

Several people tried to get to the bottom of it. The 1964 New York Times article describes the theory of Dr. F. W. Went. Went's theory, then tested by Dr. Reinhold A. Rasmussen and others, explains, "In 1960, Dr. Went advanced the idea that the blue hazes originated in vapors thrown off by trees—'molecularly dispersed organic substances derived from plants,' as he expressed it. He went on to theorize that 'under the influence of light, this material condenses and produces a blue haze.'"

UNC-TV summarizes the reasoning and writes, "The amazing amount of vegetation in the Blue Ridge Mountains, especially the conifers, release what are called Volatile Organic Compounds. VOCs are organic chemicals that easily form vapors at normal temperatures and pressures. The classes of VOCs called terpenes are naturally occurring hydrocarbons emitted by conifers. In the wild and in large numbers, all of those tiny molecules react with natural ozone molecules already in the air to form new particles and scatter blue light from the sun." Light scattering creates the bluish haze the eye can detect over the mountains.

You can learn more about the natural phenomena of the Blue Ridge Mountains at nps.gov.

Have you ever visited the Blue Ridge Mountains? What's your favorite natural wonder in the South?

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