Answer:Layer of soil that always stays frozen
Explanation:permafrost are layer of soil that remain frozen, they contain soil,sands particles and rock that have been bound together by Ice. This happens when temperature is lowered in the soil below 0°C causing water between the rocks, cracks and soil to turn to ice.
Permafrost could be of detrimental effect when it decompose in warm temperature it could lead to release of gases that causes ozone layer depletion and release of some pathogen that are toxic to health. Permafrost covers a large area of land on the world.