Here are a couple of pingos we saw along the Denali Highway. I think they were at about mile 49.
Pingo is an Inuit (Northern Eskimo) word meaning hill. The term was borrowed in 1938 by Danish botanist, Alf Erling Porsild, to describe a specific kind of hill: a rounded or conical hill having an ice core, and only found in regions with permafrost (permanently frozen soils).
There are several types of pingos. The ones shown in the photo are probably hydraulic or open-system pingos. These usually form at the base of slopes, and artesian aquifers (where water is under pressure) provide the water that forms the pingo's icy core. In this case I assume the esker to the left of the pingos is supplying the aquifers. Some open-system pingos have springs near them.