Vladimir Romanovsky, a permafrost expert at the University of Alaska-Fairbanks, has been monitoring the ice in Alaska since emigrating from Russia in 1990. In this series of photos taken in and around Fairbanks, a city built on permafrost, he shows some examples of the effects of thawing soil.

In this image, ground collapsed after surface and ground water saturated the soil. The permafrost layer begins just below the first few inches of “active layer” of soil that thaws and freezes with the seasons. Solid ice is seen in part of the permafrost layer. (Prof. Vladimir Romanovsky / University of Alaska Fairbanks)