Wood Craft Part 2 : Why Mountains Look Blue.

A strange natural phenomenon occurs in summer when it’s hot out in the backwoods. Trees like oak and popular trees release a gas naturally called isoprene. This gas combines with humidity in the air and oxidizes. This forms a natural barrier to heat and sunlight to produce a type of ozone at the ground level to protect the plants from excessive sunlight that might interfere with photosynthesis.

Maine is mostly comprised of coniferous trees and is generally cooler, so we don’t see much in the way of isoprene production. Instead of isoprene, many North American pine species emit a related volatile compound called monoterpines. In pine forests, this acts in much the same way isoprene does for other plants—defending against heat and insect stress.

But in the mountains where I grew up in western NC, this is a fairly common sight. This particular part of the Appalachians where I once lived is called the Blue Ridge. The terrain in Maine has a lot of conifers but it’s mostly deciduous trees that produce isoprene to protect the trees from heat and humidity. The ozone formed from the isoprene bends the light to show more scattering of the blue spectrum. The blue haze tends to form at outdoor temperatures starting at 77*F, and becomes very visible at temperatures from 95*F and above. Isoprene is a natural hydrocarbon that worsens air pollution, especially in areas that already have poor air quality. This is one of the reasons why I chose to move to Maine years ago. Since I have lung problems, I can actually breathe better in Maine’s backwoods versus staying and hiking in western NC where I grew up.

In the first picture above, you can see a bluish tinge starting to form here in Maine. Generally speaking, the forests of Maine are mostly coniferous and it’s the deciduous trees that release the most isoprene. Think oaks and poplars. Plus the north country tends to be a lot cooler. The second photo shows the Appalachian mountains in NC just starting to really get warmer and more humid. This is a normal sight to see.

It’s important to keep track of the temperatures in summer, so you can stay hydrated in warmer weather.