When the snow above the soil layer melts, the water remains on the surface of the soil. This is because water cannot be absorbed by the permafrost (a permanent layer of frozen ground below the soil), leaving the top layer of the soil wet and soggy. Evaporation of the water is impossible. The arctic tundra’s cool air does not allow evaporation. The arctic tundra landscape is formed by the freezing, thawing and refreezing of this soggy soil. This type of land formation is only unique to the arctic tundra. There are five types of different land formations by the power of freezing water: pingos, frost boils, bumpy ground, polygons, and stripes.
Pingos are hills which are formed by ponds of water that were trapped under permafrost. Every year, as the ponds thaw and then freeze, the hill above the ground grows taller and taller. They can grow up to 150 feet (50 meters) tall.
Frost boils are ever widening circles of stones caused by the thawing and freezing of water. As water thaws then freezes, large rocks are pushed out and form growing rock circles on the soil layer.
When the ground varies, thawing and freezing occur because of plant cover, rocks, or small ponds, and bumpy ground is formed. As all these different sections of ground cover pull and push against each other, bumps, along with tiny valleys and hills can form in the ground.
Polygons are geometric land shapes that are between 10 – 100 feet (3 – 30 meters) wide and are outlined by cracks that are filled with water. These cracks can deepen and widen forming streams and (sometimes) a shallow pond. Stripes occur on hillsides when thawing and freezing cause rocks to be sorted by particle size.
Thawing and freezing of water is not the only reason the arctic tundra shapes. Earthquakes shake the ground and volcanoes shape mountains. Gravity also plays an important part. The water which causes the arctic tundra’s soggy ground flows downhill. This slow downhill flow of water is called solifluction. Solifluction is a sure-fire way that the tundra is changing.