Today we had a good long walk around the island. The purpose was just to go around and see loosely what changes might have occurred on the surface since last year and years before.

The Lena River floods regularly in spring time due to massive ice packs that are formed in the mouths of the many channels in the delta, thus blocking the water running normally through for some time. Last spring the Island got close to record flooding and some traces could be detected also on the island ground from that period.

The most spectacular as well as visible features on the ground are though the polygons, which form about two thirds of the island.

 

 

A polygon is a formation on the permafrost ground that is created by the periodical freeze and thaw of the permafrost top layer, in scientific terms called active layer. This active layer thaws over the summer period and freezes again during the winter every year. When frozen, the soil breaks up forming cracks on the ground. In spring, when the ground melts again these cracks get filled with water from melting snow and rain. Some of the water evaporates away during the warmer summer months, but some of it will stay in the cracks until the winter and freeze up forming what is called “ice wedges” below the ground.

 

 

The ice wedges are very small in the beginning, only few millimeters in diameter, but they grow with time, when more and more water runs in to the cracks during the melt period. In old polygonal landscapes the ice wedges can actually get very big, or up to many meters in diameter.

On the coasts, where erosion eats up the coast line, the polygons many times fall apart from the mainland ground in one big formation. Exactly this type of land erosion can be found in some places on the coast of Samoylov. In the picture here below is one of the bigger open ice wedges that we found during our walk.

 

 

 

Here the river has eroded the land mass underneath the polygon up to the point where the bottom-up support has been so weak that the remaining top layer of the ground has broken up at the edge of the polygon and fallen down revealing the large ice wedge.

The erosion process is very similar as the one described in the info graphic here below, with the exception that here on the island we have no trees and the little infrastructure that has been build, is on locations where the erosion is at the minimum.