PERMAFROST

Why in news: The Annual Arctic Report Card by US National Oceanic and Atmospheric Administration stated that that the Arctic is in warmest year since 1900.

• Permafrost is any ground that remains completely frozen—32°F (0°C) or colder—for at least two years straight.
• Global Distribution:
  • These permanently frozen grounds are most common in regions with high mountainsand in Earth’s higher latitudes—near the North and South Poles.
  • Permafrost covers large regions of the Earth. Almost a quarter of the land area in the Northern Hemisphere has permafrost

• Composition:
  • Permafrost is made of a combination of soil, rocks and sand that are held together by ice.The soil and ice in permafrost stay frozen all year long.
  • Near the surface, permafrost soils also contain large quantities of organic carbon—a material leftover from dead plants that couldn’t decompose, or rot away, due to the cold.
  • Lower permafrost layers contain soils made mostly of minerals.
  • A layer of soil on top of permafrost does not stay frozen all year. This layer, called the active layer,thaws during the warm summer months and freezes again in the fall.