Evidence of Cryoseism

Evidence of Cryoseism

Ice jacking at Sunset Beach, Lac Ste. Anne Thibeault Settlement, Lac Ste. Anne
The ice jacking process deformed the soil at Sunset Beach, Lac Ste. Anne, Alberta following rapid temperature increases on January 1, 2018. Thibeault Settlement on Lac Ste. Anne, Alberta, following rapid temperature increases on January 1, 2018.  (ruler for scale indicates one metre)

 

Cryoseism can potentially cause damage to nearby structures depending on the intensity of and proximity to the event. Evidence of cryoseism may include fractures in the ground or ice and pressure ridges near a shoreline.  Given the right conditions, heaving sediment or folding of rock or ice can continue gradually over longer time frames and cause damage to property. Such damage can be seen as structural foundation cracks, shifting of buildings, or cracks in walls.

 

Ground crack, Devon
Pressure ridges developed at Lac Ste. Anne after an icequake that occured after rapid temperature increases on January 1, 2018 Ground cracks developed near the Town of Devon around the same time period (ruler for scale indicates one metre)

 

Gazebo with ice heave at Lac Ste. Anne Gazebo with ice heave at Lac Ste. Anne
Soil deformation from ice heave, January 5, 2018, Lac Ste Anne Soil deformation from ice heave, January 19, 2018, Lac Ste Anne

Where Cryoseism Occurs

Frostquakes and frost heave are most likely to occur in areas with loose rock or sediment such as sand and topsoil because these soil types are very permeable (liquid can move easily through them). The permeability of these types of sediment depends on how well compacted they are – increasing water movement through the sediment if it is lightly packed, or decreasing if it is tightly packed. Areas with more permeable soil are more likely to experience frostquakes and frost heave because the saturated soil is highly prone to changing atmospheric temperature. However, packed material such as asphalt and concrete can also experience frostquakes, when the material can’t accommodate the sudden volume change due to a rapid temperature change.

Icequakes can occur on glaciers and frozen bodies of water such as lakes. An icequake may occur when the increasing temperature causes an expansion of the top-most frozen part of the large body of water. This causes increased pressure on the ice, and if the surface ice pressure is greater than the shoreline strength, the ice could fracture and form ridges on the surface. Lake ice can bond to the sediments along or close to the shoreline making them brittle and prone to more violent ruptures, or the process of ice heaving can occur, if the ice remains separate from the sediments.

Conditions Favouring Cryoseism Events

Minimal snow cover is required for both types of cryoseisms and for both types of ground heave. Where there is minimal snow cover, the saturated soil is not well insulated from rapid changes in atmospheric temperature – thus a sudden contraction of the soil can occur, developing fissures on the surface that could lead to frostquakes or frost heave. Also, lake ice can expand due to the absence of snow insulation that could lead to icequakes and produce surface pressure ridges or ice heaves and expand the ice onto the shore. These processes mostly happen during the coldest part of the day, which is usually at night.

Cryoseisms occur as single or multiple events. Numerous cryoseisms can occur during consecutive cold days or nights and can contribute to the growth of cracks and further develop soil deformations.