During periods of severe cold, unusual ground-shaking noises known as frost quakes or cryoseisms can occur as a result of rapid freezing of moisture in the soil. These events transpire when rain or melted snow embedded in the earth solidifies quickly after temperatures plunge below the freezing point. The process of water turning into ice causes expansion, creating significant pressure on the surrounding soil. As a consequence, the ground can crack, emitting loud booming sounds accompanied occasionally by light vibrations.
Evan Webb, a meteorologist with the National Weather Service office in Louisville, Kentucky, explained that their company has received multiple accounts of "loud booms" linked to cryoseisms during episodes of bitter cold weather. Webb pointed out that people often initially suspect "exploding trees" or other more dramatic causes for these noises when they occur.
Instances of frost quakes have been documented in various cold regions, though Webb noted they remain "relatively rare, especially in Kentucky." This rarity is attributed to infrequent conditions combining saturated soil during winter and a rapid temperature drop sufficient to freeze the moisture swiftly. The meteorologist emphasized that while frost quakes may be alarming, they are generally "mostly harmless". He added that the prevailing single-digit temperatures, especially when factoring in wind chill, pose a more significant threat than these brief seismic events.
Social media commentary from the National Weather Service office also mentions frost quakes, highlighting that although the sudden noises can be startling—particularly at night—there is no need for alarm. They clarified that these booming sounds are not paranormal occurrences but rather natural cryoseismic events caused by environmental conditions.
Photographic imagery from a winter storm event in Owensboro, Kentucky, captured scenes such as a bicyclist riding through snow-covered roads, underlining the severe weather conditions that can accompany frost quake phenomena.
Overall, frost quakes serve as a reminder of the complex interactions between meteorological patterns and geological responses during extreme cold. While they do not present significant physical risk, their occurrence provides insights into soil behavior when subjected to rapid freeze-thaw cycles.