When the air temperature of a region falls below the freezing point of the water (0 ° C), frost may occur. It occurs because the water vapor in the air, falling at night, turns into ice crystals.
Rebecca realized that after a frost, a stone presented a crack that was probably caused by frost. The order that this phenomenon occured for this crack to appear was:
- Rain water is stored in rock and seeps into a hairline crack during a rainfall: It is probable that this rock had small fissures, by where the rain water infiltrated and was stored there.
- The temperature falls below 0° Celsius: As previously stated, frost only occurs when the temperature of a region falls below 0 °C
- Rainwater in the rock crack freezes into ice: At such a low temperature, the water present in the cracks of the stone froze
- Because ice occupies more space than water, the ice wedges the crack open: When the water froze, it turned to ice and expanded in size. Ice takes up more space than water, so ice forced the small cracks in the stone to crack.
- The freeze-thaw cycle continues to deepen the crack until the rock splits into 2 pieces: The freezing causes the ice to expand more and more and this deepens the cracks in the stone.