Snow Avalanches PDF

snow avalanches Monday, 25 November 2024 15:52 A mass of snow many cubic metres in volume that separates from a snowpack and moves downslope The intensity of an avalanche is...

snow avalanches Monday, 25 November 2024 15:52 A mass of snow many cubic metres in volume that separates from a snowpack and moves downslope The intensity of an avalanche is dependent on slope steepness, snowpack stability, and weather. New Section 1 Page 1  An avalanche travelling as a coherent block An avalanche that becomes wider as it travels downslope It is es New Section 1 Page 2 The sliding snow then causes more failures in the adjacent snowpack causing the trough to widen New Section 1 Page 3  It occurs when a snowpack fractures along a weak layer in parallel to the surface. The avalanches move as cohesive blocks leaving behind a scarp A mass of snow that is above the vegetation level and above large boulders is more likely to slide. New Section 1 Page 4  Wind can deposit a layer of light ice crystals in a layer of more compacted snow The boundary in between the two layers could become a horizon along which failure could occur Hoar can form deep in the snowpack (in air pockets) or snow surface New Section 1 Page 5  The fastaest avalancghes have been measured at Speeds near 20km/h Avalanches that cause injuries or fatalities are often triggered by people( their activities) Some avalanches are triggered intentionally with explosives New Section 1 Page 6  The area where the avalanche accelerates and Reaches maximum velocity The area of deceleration and snow deposition Most avalanches occur at slope angles between 25 degrees and 60 degrees At angles below 25 degrees, snow does not easily slide New Section 1 Page 7  The orientation of the slipe can also be a factor Orientation is just the direction that slope faces Other factors include the smoothness of the slope, the amount of vegetation, and the topography of the slope itself In North America, deep snowpacks are mostly common in the Rocky Mountains New Section 1 Page 8  In total, over 600 people have died forma avalanches in Canada Damages to forests is evident each year but property damage is relatively minor An avalanche spread over the ChilKoot trail causing 60 deaths The ChilKoot New Section 1 Page 9  Some areas will experience more thaws in winter enhancing the instability of the snowpack New Section 1 Page 10  Avalanches maintain open areas in to otherwse forested regions This can serve as an important habitat zone for certain plants and animals Avalanches only become a hazard when humans encroach on areas that are prone to them New Section 1 Page 11  Hazard maps provide planners with location of the highest risk areas In avalanche start zones, fences or nets can be installed to stabilize the snowpack New Section 1 Page 12  Splitting wedges on the sides of buildings can force and avalanche around the structure. New Section 1 Page 13  - Location of past avalanches - Strength and stability tests - Snowpack observations - Weather New Section 1 Page 14  A column of snow is isolated and then a force is applied on the uphill side A skier pushes and jumps on a column of snow to determine the cohesion of a snowpack New Section 1 Page 15  It was a chart designed to warn travellers of the risk of an avalanche in an area Over 90% survive if rescued within 15 minutes, 30*% within 35 minutes, and 0% within 2 hours Buried victims die of a combination of suffocation and hypothermia New Section 1 Page 16  Less than 10% of victims survive burial in more than 1.5m of snow A 10 m rope that drags behind a person while skiing, snowboarding, or snowshoeing A portable device that emits a radio signal to assist in finding the location of a victim They can detect human scent rising through the snow and can quickly cover large areas New Section 1 Page 17