Loud booms and a shuddering house were reported by a FOX19 viewer from Hidden Valley Lake Monday evening.
She thought it may be the result of freezing sap which expands then splits the tree's wood. That is a possibility, but trees usually split from air colder than what we have been experiencing. Trees usually split when air temperatures are colder than minus 20. Usually a limb falls and splinters when it hits the ground creating the noise. Trees exploding from freezing sap are very rare. Lightning though can cause a tree to explode.
More likely, what our viewer was hearing and feeling was what are called "frost quakes". The technical term is "cryoseism" and they are caused 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 are saturated soil and thin or no snow cover. Soils around here are wet because of the rain Sunday and there is virtually no snow cover to insulate the soil from the effects of the cold air.
According to Wikipedia the first frost quake reported in the United States was in 1818.
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