Loud booms and a shuddering house were reported by a FOX19viewer from Hidden Valley Lake Monday evening.
She thought it may be the result of freezing sap whichexpands then splits the tree's wood. That is a possibility, buttrees usually split from air colder than what we have beenexperiencing. Trees usually split when air temperatures are colder than minus 20. Usually a limb falls and splinters when it hits the ground creating thenoise. Trees exploding from freezing sap are very rare. Lightning thoughcan cause a tree to explode.
More likely, what our viewer was hearing and feeling was whatare called "frost quakes". The technical term is "cryoseism" and they arecaused when saturated soil freezes in near zero or below zero weather. The soil, frozen solid, suddenly cracks because of expanding ice.
Two conditions which help make cryoseisms possible aresaturated soil and thin or no snow cover. Soils around here are wet because ofthe rain Sunday and there is virtually no snow cover to insulate the soil fromthe effects of the cold air.
According to Wikipedia the first frost quake reported in theUnited States was in 1818.