Abstract
During and after the last ice age, several hundred meters of glaciomarine and marine
sediments accumulated in Norwegian fjords. These deposits have subsequently
emerged due to glacioisostatic rebound, and leaching of salts from the marine clay by
groundwater has resulted in the development of “quick clay” in layers or pockets.
During a quick-clay slide, dated to about 3000 14C-years BP, a 200 000 m2 large
“bottle-neck”-shaped slide scar was formed in Buvika, Mid Norway. This welldefined
slide scar, among numerous slide scars mapped in the valley, is typical for
terrains in marine clays and has been the subject of several types of investigations.
Electric resistivity measurements, refraction seismic investigations and geotechnical
drillings have been carried out to outline the stratigraphy of the area of the slide scar.
The investigations show that some clay, mainly slide deposits, covers sand and gravel
below the slide scar. The sand and gravel directly overly bedrock. Water draining
from the steep rock face west and south of the Saltnes slide scar has been stored in the
buried coarse deposit creating an artesian water pressure. This probably accelerated
the quick-clay development. The river level at the estimated time of the slide was
probably near the level of the failure surface. River erosion most likely triggered the
slide, possibly in combination with high pore-water pressures. The scar was more or
less emptied during sliding, which is common when large amounts of quick clay are
remoulded. Some slide material was also left behind in the scar, as deformed blocks.
A section through a sediment block in the Saltnes slide scar shows intact layering,
while the outer edges are deformed.
The study shows that interdisciplinary studies, combining geology,
geomorphology, geophysics and geotechnics, give a more complete picture of the
conditions of the slide event.
sediments accumulated in Norwegian fjords. These deposits have subsequently
emerged due to glacioisostatic rebound, and leaching of salts from the marine clay by
groundwater has resulted in the development of “quick clay” in layers or pockets.
During a quick-clay slide, dated to about 3000 14C-years BP, a 200 000 m2 large
“bottle-neck”-shaped slide scar was formed in Buvika, Mid Norway. This welldefined
slide scar, among numerous slide scars mapped in the valley, is typical for
terrains in marine clays and has been the subject of several types of investigations.
Electric resistivity measurements, refraction seismic investigations and geotechnical
drillings have been carried out to outline the stratigraphy of the area of the slide scar.
The investigations show that some clay, mainly slide deposits, covers sand and gravel
below the slide scar. The sand and gravel directly overly bedrock. Water draining
from the steep rock face west and south of the Saltnes slide scar has been stored in the
buried coarse deposit creating an artesian water pressure. This probably accelerated
the quick-clay development. The river level at the estimated time of the slide was
probably near the level of the failure surface. River erosion most likely triggered the
slide, possibly in combination with high pore-water pressures. The scar was more or
less emptied during sliding, which is common when large amounts of quick clay are
remoulded. Some slide material was also left behind in the scar, as deformed blocks.
A section through a sediment block in the Saltnes slide scar shows intact layering,
while the outer edges are deformed.
The study shows that interdisciplinary studies, combining geology,
geomorphology, geophysics and geotechnics, give a more complete picture of the
conditions of the slide event.
