Palsa near Cranberry Portage, Manitoba.



This image gives a good cross section of the permafrost development in the peat and clay layer. The fieldwork for this diagram was carried out between 1968-1970 by two of my forest ecologist friends Steve Zoltai and Charles Tarnocai.

This cross section is very indicative of the situation described in the first post on permafrost melting just north of Lake Winnipeg. The glacial lake Agassiz clays form the mineral layer, which is covered by up to two meters of organic material. Permafrost extends into the clay layer. Onviously the premafrost was developed after the galcial lake retreated and the organic layer formed. It is actually the result of a very intricate interaction of climate, microclimate and forest cover and insulating properties of sphagnum mosses.

More information at

http://www.geostrategis.com/p_mapm2.html
and
www.ecoinformatics.com