Monday, August 25, 2014

Interesting Geomorphological Features in the Landscape…

According to Wikipedia, solifluction is a gradual mass wasting slop process, occurring in periglacial environments. It is the slow downslope movement of water-saturated sediment due to recurrent freezing and thawing of ground. The lobes formed through the solifluction process are quite distinctive and easy to see as you drive through the area.

We have seen evidence of solifluction at several locations this week and today we took the opportunity to visit one such site on a modest hillslope just 15 to 20 miles outside Nome on the Teller Road. Joel and Eitan spend the afternoon excavating a small section of an advancing lobe trying to better characterize thaw depth, ice content, soil texture, and moisture content. Larry, David, and Cathy took time to collect soil cores from across the lobes and adjacent areas, as well as quantify the spatial variation in thaw depth across the area. Since one of these solifluction features can cover an entire hillslope I took the afternoon to walk each lobe and examine the distribution of water and vegetation along the advancing front. It was clear that the lobes were fairly massive with most of them being multiple meters in height. The advancing faces of these features were heavily colonized by willow shrubs. These shrubs were quite productive and seemed to thrive in areas of physical disturbance. Downslope of the advancing face the soils were saturated and vegetation was largely sedges and forbs. So these geomorphological features created a highly variable environment for vegetation cover. The implications for albedo, energy balance, and the carbon cycle of these solifluction features are unknown, but they represent interesting features in the landscape. While the solifluction process itself may not be of interest to our NGEE Arctic team, the mechanisms that promote shrub expansion are and we will want to return to this and other disturbed areas in order to learn more.