Soil below the surface of a tundra that remains frozen permanently is called permafrost. Permafrost is a layer of soil, rock, and ice that remains at or below freezing point (0°C or 32°F) for at least two consecutive years. It is found in the Arctic, Antarctic, and high-altitude mountain regions and can be several hundred meters deep. Permafrost plays an important role in the tundra ecosystem by affecting the water cycle, nutrient availability, and plant and animal habitats. However, due to climate change, permafrost is thawing at an alarming rate, which is causing significant environmental and social impacts in these regions.