The tundra has a variety of landforms that are unique to the frozen landscape. Pingos, frost boils, bumpy ground, polygons and stripes all form under the conditions present only in the tundra.
In the tundra, the topsoil freezes, thaws and then refreezes. The topsoil is abnormally pushed and pulled during this process. However, when plants, rocks and bodies of water get in the way as the topsoil is pushed along with the frost, it creates tiny hills, valleys, slopes, bumps and porous regions, aptly called bumpy ground.
When water that is trapped under the permafrost freezes, it heaves upwards due to pressure. Year after year, the frozen, underground water grows upwards, sometimes up to 50 meters tall. These are called pingos. Pingos are also formed when permafrost surrounds a body of water, which later freezes and turns into a mound.
During the freezing and thawing of water above the permafrost, the frost pushes rocks outwards in ever widening circles called frost boils. Stripes are formed in the same manner as frost boils. When frost boils occur on hills, the rocks end up separated by size and form stripes. Water can also get trapped in cracks in the ground. When the water freezes, it expands, creating geometrical shapes in the ground called polygons, which can be anywhere between three and 30 meters wide.
Mountains, lakes and even islands are all part of the landforms found in the tundra.