Often times, we here of stories of mysterious explosions and booming sounds that seem to emanate from nowhere and even shake and rattle homes. These are often associated with various conspiracy type stories of secret government experiments, HAARP weather modification, and even sometimes aliens. The frequency of reports of these have many folks baffled as to their source.
These mysterious booms and rattles do have a natural source though and they are called, cryoseisms. A more common term for this might be frost quakes. A cryoseism occurs from a sudden deep freezing of the ground. But more particularly a sudden freezing of the ground where water is present in the ground. Water expands when it freezes. When the water in the ground freezes it exerts pressure on the rock to the point where the rock snaps, releasing an audible boom sound and generating a very local shock wave, much like an earthquake.
Because of the very local nature of these events, they rarely are measured by a Richter scale. Your home could get a good rattling though if you are right near one of them. The audible boom can go out further from the ground shake. This leaves people confused too because there seems to be no visible connection to the sound being heard.
Frost quakes have nothing to do with earthquakes, movement of tectonic plates, volcanoes and other factors are unrelated to surface temperature. Frost quakes usually occur between midnight and dawn, the coldest part of the night. They can occur over several hours and even several days. They are most common after a cold rain or thaw event when arctic cold sweeps in afterwards. They can occur anywhere where the temperatures can drop cold enough to cause a rapid freeze. They very rarely cause any damage, but they sure can get people excited.
Not to long ago I received a question from someone about ice storms. Today I want to answer the question as well as give a whole picture of what an ice storm is, and how it occurs, and the specific question as to why it occurs more in certain areas of the US.
An ice storm is basically a rain event where the rain falls into air that is at or just below freezing. When the water makes contact with objects, it then freezes into ice. This ice continues to build as long as it keeps raining and staying below 32 degrees. Water is quite heavy so once the ice reaches a certain point, the things the ice is forming on can no longer carry the weight and begin to break. Tree Branches and power lines are the most vulnerable, and of course anything that happens to be under those falling trees is subject to damage as well.
An ice storm forms when warm air is moving over the top of a shallow layer of cold air on the surface. Cold air is generally heavier so you can get very thin layers of below freezing temperatures that collect near the surface while warmer moisture filled air is thrown over the top of that cold layer. If the surface cold layer is too thick, you end up with ice pellets or snow. Generally you get ice storms on the north side of a warm front where the warm air is trying to move in.
You can get ice storms anywhere in the US, but as my questioner asked, why is it the mid south and south seem to get more ice storms than other areas of the country? These areas are more prone to ice storms because of their geographic location. You get ample warmth and moisture from the Gulf of Mexico and the cold air streaming down from Canada is generally running out of steam in it push south. This provides the best environment for major ice storms.
Ice storms do have a beauty to them though, as well as the capability of being highly destructive. These types of storms can so devastate an area that it can knock it back into the pre-electric area for weeks. They can also be unbelievably beautiful when not as thick. It is one of the weather issues that we need to be prepared for as it can knock out power and transportation for extended periods. We also need to be aware of it's deadly nature. Falling objects, live power lines, and an inability to navigate are all dangers that can harm or kill us.
