Cryoseisms, commonly known as frost quakes, are non-tectonic seismic events that occur when water underground rapidly freezes and expands. Unlike typical earthquakes caused by the movement of tectonic plates, cryoseisms are purely localized, weather-driven phenomena. For a frost quake to occur, a specific sequence of meteorological conditions must align. First, the ground must be saturated with water, usually from recent rainfall or melted snow. Second, there must be little to no snow cover, because a thick layer of snow acts as a thermal insulator, preventing the subzero air from directly cooling the ground. When a sudden, extreme drop in temperature occurs under these conditions, the moisture trapped in the soil pores freezes rapidly. Because water expands by approximately when transitioning to ice, it exerts immense pressure on the surrounding soil and rock. Once this pressure exceeds the structural strength of the earth, the ground cracks open, generating a loud booming noise and shaking that can be felt nearby.
According to the passage, what is the direct cause of the ground cracking and generating a booming noise during a cryoseism?
- AThe sudden cracking of the ground forcing the water in soil pores to expand and freeze
- BThe insulation provided by a thick layer of snow during an extreme drop in temperature
- The pressure exerted by the expanding ice exceeding the structural strength of the soil and rockAnswer
- DThe movement of tectonic plates driven by rapid temperature fluctuations