These are some photos of several pingos that dot the Noatak Flats. A pingo is formed by a compicated process involving ice. It is a phenomenon that is said to occur only where there is permafrost.
Underneath the tundra is permafrost, ground that is perpetually frozen year round. The tundra is dotted with many lakes and ponds. Some of these lakes, if they are the right size and deeper than about 7 or 8 feet, do not freeze solid in the winter.
Because the lake does not freeze all the way, the permafrost underneath it melts. This creates an unfrozen layer of waterlogged soil between the lake water and the underlying deep permafrost.
A pingo is formed when one of these lakes die. If the lake drains or becomes more shallow it is much more likely to freeze solid in long winter. The water soaked soil at the bottom of the lake also freezes and expands. The soil on top of the water freezes from the top down as it also freezes from the bottom permafrost layer up.
The feezing soil cannot handle the excess water and as the area continues to contract, the unfrozen water is squeezed under tremendous pressure. Over hundreds of years of time the water is under such pressure that it begins to push upwards and the water gets trapped underneath the top layer of permafrost that formed after the lake drained. This causes the top layer to rise and forms the pingo.
Pingos are interesting to look at, but they are also useful. Not only to they break the monotony of a vast flat area such as the Noatak Flats and serve as helpful landmarks, but they also provide a high point in the land which makes a good lookout while hunting.