23 December 2010

Frost Flowers In Alabama

Posted by Dan Satterfield

Frost Flowers in Huntsville Alabama. Ctsy. Joni Atkins.

A couple of viewers sent me some pictures of strange ice formations today. They are very beautiful (and rather rare) specimens of what are called “FROST FLOWERS”.

Another frost flower from Jim Reid who took this shot near Paint Rock, AL.

They form in areas where the ground is still warm but the air is quite cold. You usually see them after a sudden but intense cold snap. I’ve only seen them one time, but have been on the lookout for them ever since!

What’s likely happening is this: Water is rising from the warm ground into the stems of certain plants. It then flows out of cracks in the stems and suddenly freezes. The water may be supercooled, i.e. below freezing, but still a liquid. As it extrudes from the cracks in the stem, the water touches ice crystals on the stem, and ice immediately forms.

A good video on supercooled water from you tube shows how quickly water in this state can freeze. It just takes one crystal to start the process.

As water continues to rise in the plant (through capillary action) a ribbon of ice forms, and can curl into a flower like ice sculpture.

There are some incredible examples of this type of ice formation on a web page by Dr. James R. Carter at Illinois State Univ. He even wrote an article about them in WEATHERWISE magazine in 2009.

I suspect that frost flowers are more common in areas where the ground rarely freezes, but occasional cold snaps in winter can bring very cold temperatures. Some of the best examples I have seen are from Alabama and Tennessee. I kind of like the idea of making frost flowers the official Alabama state flower.

Unfortunately, it will be pretty hard to knock the Camellia out of that spot! Tennessee has the iris, and even I wouldn’t go that far ;)