Landslides are a natural geological occurrance happening constantly through out the World with major effects on our habitant.
Landslides can be very fast moving and terribly destructive. Famous slides such as The Frank Slide in Alberta , The Hope Slide in BC and most recently the Chilcotin River Slide that blocked the river in BC. Landslides such as these dramatically alter the landscape , harming both civilian and animal life.
Landslides, also known as landslips, skyfalls or rockslides, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, mudflows, shallow or deep-seated slope failures and debris flows. Landslides occur in a variety of environments, characterized by either steep or gentle slope gradients, from mountain ranges to coastal cliffs or even underwater, in which case they are called submarine landslides.
Gravity is the primary driving force for a landslide to occur, but there are other factors affecting slope stability that produce specific conditions that make a slope prone to failure. In many cases, the landslide is triggered by a specific event (such as heavy rainfall, an earthquake, a slope cut to build a road, and many others), although this is not always identifiable.
Landslides are frequently made worse by human development (such as urban sprawl) and resource exploitation (such as mining and deforestation). Land degradation frequently leads to less stabilization of soil by vegetation. Additionally, global warming caused by climate change and other human impact on the environment, can increase the frequency of natural events (such as extreme weather) which trigger landslides. Landslide mitigation describes the policy and practices for reducing the risk of human impacts of landslides, reducing the risk of natural disaster.
Cause
Landslides occur when the slope (or a portion of it) undergoes some processes that change its condition from stable to unstable. This is essentially due to a decrease in the shear strength of the slope material, an increase in the shear stress borne by the material, or a combination of the two. A change in the stability of a slope can be caused by a number of factors, acting together or alone. Natural causes of landslides include:
- increase in water content (loss of suction) or saturation by rain water infiltration, snow melting, or glaciers melting;
- rising of groundwater or increase of pore water pressure (e.g. due to aquifer recharge in rainy seasons, or by rain water infiltration);
- increase of hydrostatic pressure in cracks and fractures;
- loss or absence of vertical vegetative structure, soil nutrients, and soil structure (e.g. after a wildfire)
- erosion of the top of a slope by rivers or sea waves;[
- physical and chemical weathering (e.g. by repeated freezing and thawing, heating and cooling, salt leaking in the groundwater or mineral dissolution);
- ground shaking caused by earthquakes, which can destabilize the slope directly (e.g., by inducing soil liquefaction) or weaken the material and cause cracks that will eventually produce a landslide;
- volcanic eruptions;
- changes in pore fluid composition;
- changes in temperature (seasonal or induced by climate change).[
Landslides are aggravated by human activities, such as:
Types
There are ten different types, - A - Rotational Landslide , B - Transitional Landslide , C - Block Slide, D - Rockfall , E - Topple , F - Debris Flow , G - Debris Avalanche , H - Earthflow , I - Creep , J - Lateral Spread
Our main subject here is Creep. The long term effects of Creep are seen across the country.
Creep is a category of Landslide that has always been happening on hills and valley sides at much slower speeds
As the population increases the need for housing and industrial sites is increasing. Valley edges are often sought after as premium building sites with outstanding scenic views. The ultimate risk is long term Landslipage. The Valley through the City of Lethbridge has major creep affecting countless structures. Similar effects are seen along valleys in Saskatchewan and Manitoba. The views eventually leading to major drops in property - monetarialy and physically.
Morden , located at the foot of the Escarpment is expanding up and over the leading edge. Country homes are becoming more numerous along the top edge for the scenic overlooks.
The escarpment is also comprised of glacial material that was deposited as moraines during multiple glaciations and by a succession of beach deposits formed at the margins of Glacial Lake Agassiz. The Manitoba Escarpment originated as an erosional feature that developed as a consequence of the Laramide Orogeny, which occurred 84 to 50 Ma. With glacial till over gravel deposites long term slipage is constantly evolving. With the removal of native grasses and trees deformation is speeding up.
With the above knowledge as you travel the countryside the extent and causes can be recognized.
This site displays landslipage in the early stages.
To claim this Earthcache please provide your asnswers to the following question prior to logging.
1) Does it appear the tree cover would prevent further slipage ?
2) The region is rich in gravel deposites. Do you think that effects the creep?
3) There is a sign on the west side of the road. What structure is described ? What affect on the valley edges to the east would it have ?
4) Provide a photo of your gps devices or an identifier of you at the site .
Thank you