Ice Pillars: What Causes This Light Pillar Phenomenon?
Ice pillars, also called light pillars, are an optical effect where a “pillar” or beam of light appears to extend vertically below, and more noticeably above, the source of that light. This light pillar phenomenon is somewhat rare, but when it occurs, it provides a beautiful light show over the night sky as can be seen in the mage above. This photo captures an awesome display of ice pillars on a winter evening over West Virginia.
The ice pillars are actually playing tricks on our eyes however. No matter how real they appear to be emanating light upwards, these light pillars are merely an optical illusion. The light is not actually beaming up to the heavens above!
What Causes Ice Pillars?
Ice pillars are caused by lights reflecting off the surface of horizontal ice crystals low in the atmosphere. These plate-like ice crystals are hexagonal in shape and are commonly falling slowly to the earth’s surface, similar to a feather floating in the air. In other instances, the ice crystals are suspended in the air for some period of time, such as the case with freezing fog. When these crystals get low enough in the atmosphere, they create the illusion of the ice pillars.
Answering the question, how are light pillars formed, is easier after looking at the sketch above. You can see why the ice pillars are more of a projected illusion and not actual light beams. Similar to rainbows, the light pillar phenomenon requires you to be a distance away from the ice crystals and the light source to be on the opposite side. For this reason, you cannot actually locate these ice pillars in space because their projection moves as you move!
Where Do Light Pillars Form?
Technically, they can form anywhere there is a light source combined with horizontal ice crystals low in the atmosphere. Since these ice crystals are required to be present to form these pillars of light, they are almost exclusively found during very cold conditions and often reported in areas that see these conditions more often than others, namely the northern United States and Canadian regions like this report in Wisconsin.
Some of the coolest images found of light pillars show artificial lights such as street lamps and other brightly colored lights found emanating in pillars over a city. This is mainly due to the neat colors reflected on the dark night sky since the light pillar takes the color of the source it comes from.
Ice pillars do not require the light be artificial however, sun pillars and moon pillars also occur in the same frigid conditions. The concept is exactly the same as shown in the sketch above, but in sun pillars, the vertical shaft of light appears to extend out of the sun itself rather than a street lamp. The same applies for moon pillars. I think we see these images less often because they are less dramatic than the colorful ice pillars shown over city lights on the dark back ground of the night sky.
I’m fascinated with these images mentioned above. There are photographers that have made a living finding such images. 500px posted an entire collection of photos they titled as “Beam Me Up Scotty” showing the light pillar phenomenon.
I encourage you to go take a look. I can’t get enough of these pictures. They are so cool!