Permafrost Thaw Slide, Caribou River Area, Yukon, Canada.kmz

Permafrost Thaw Slide, Caribou River Area, Yukon, Canada
This foldercontains a description of the retrogressive thaw history. The various thaw stages are illustrated with two airphoto overlays representing the start of the slide (1950) and the intermediate stage (1977). Google Earth itself shows the situation in the summer of 2007.
Source of location: Kingpointnorth, Google Earth BBS
Interpretation: Jean Thie, Ecoinformatics International
More Information: www.geostrategis.com

Permafrost Thaw Slide, Caribou River Area, Yukon
SITE 2: Retrogressive Permafrost Thaw Slide, Caribou River, Yukon Territories, Canada
Source of location: Kingpointnorth, Google Earth BBS documented August, 2005
Interpretation: Jean Thie, Ecoinformatics International
More Information: www.geostrategis.com
Figure 1 The Permafrost slide area as seen on Google Earth 2007 : original source 2007 Digital Globe high resolution image. The red marker is from the selection of regressive permafrost slides marker selection provided by Kingpointnorth. The relative recent disturbed bare soil is clearly visible on both sides of the creek. Also the adjacent areas on both sides show significant sliding area which appear to have been stabilized and are recovered with vegetation.
This site is within the Peel River Plateau Ecoregion and the Taiga Plain Ecozone. The landscape is almost entirely shaped as result of the Laurentide glaciation, and post glacial fluvial and other geomorphological processes. Continuous permafrost is present with depth to base of ice-bearing permafrost close to 300 m (Geological Survey of Canada, unpublished data). Retrogressive thaw flow slides are common where ground ice has been exposed in glaciolacustrine deposits by forest fires, debris flows and regressive erosion. (Ecoregions of the Yukon: Peel River Plateau).
Figure 2 Interpretation of the History of the Permafrost Slide Area.
This figure represents the air photo and satellite image interpretation since 1950. The earliest available air photos taken in 1950 showed that the first slide started on the right side of the creek, in effect the south facing slope. It appears to have been a sudden event. The pink arrow shows the slide path, which also blocked the creek flow, and created a small lake upstream. The the water erosion from the displaced creek started to undermine the north facing slope which showed a steady regression for the next 27 years before stabilizing. Just before the 1990's additional regression occurred on the south facing slope (thin orange line) also occurring as a sudden failure. The new slide areas (yellow dotted line) developed between 1990 and 2000.
Figure 3. Retrogressive Slide on 1950 and 1953 Aerial Photos
The 1950 photo was taken on August 2nd at a height of 20'000 ft. Original scale 1:40'000. The pink arrow shows the flow direction. The slide, on the south facing slope occurred as a sudden event blocking the flow of the creek and creating a small lake upstream. The drainage channel was pushed into the opposite slope which started to collapse. Both sides continued to melt, but most of the regression in the following decade is in the north facing slope.
Figure 4. The Next 20 Years
During the next 20 years the North facing slide is regressing. The 1972 and 1977 air photos show that the creek is pushed back again (yellow marker). In this 5 year period the North facing slide appears stable, and some further sliding occurred on the south facing slide (from blue dotted line to the light blue-grey dotted line). There are no signs of fire scars in the vegetation on these photos.

1950 Air photo overlay showing start of permafrost slide
SITE 2: Retrogressive Permafrost Thaw Slide, Caribou River, Yukon Territories, Canada.
Source of location: Kingpointnorth, Google Earth BBS
Interpretation: Jean Thie, Ecoinformatics International
More Information: www.geostrategis.com
1950 air photo overlay on Google Earth
The 1950 photo was taken on August 2nd at a height of 20'000 ft. Original scale 1:40'000. The pink arrow shows the flow direction. The slide, on the south facing slope occurred as a sudden event blocking the flow of the creek and creating a small lake upstream. The drainage channel was pushed into the opposite slope which started to collapse. Both sides continued to melt, but most of the regression in the following decade is in the north facing slope.

1977 Air photo overlay
SITE 2: Retrogressive Permafrost Thaw Slide, Caribou River, Yukon Territories, Canada.
Source of location: Kingpointnorth, Google Earth BBS
Source of Air Photos: National Airphoto Library, Ottawa, Canada
1977 air photo overlay on Google Earth
During the next 20 years the North facing slide is regressing. The 1972 and 1977 air photos show that the creek is pushed back again (yellow marker). In this 5 year period the North slide appears stable, and some further sliding occurred on the south facing slide (from blue dotted line to the light blue-grey dotted line). There are no signs of fire scars in the vegetation on these photos, but a fire scars ( (dated between 1958-1978) were identified in close to the Salter Hill area, about 5 km distance from this slide area. 1972 Airphoto (A22972-119) taken on 11 July, from 35'000 ft; 1977 air photo (A24761-133) taken on August 1, from 35'000 ft.