Zopkios Ridge -- Avalanches 101
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The info you need for this earthcache is located at the Coquihalla Summit rest stop, where there are washrooms, a payphone, and sometimes a snack van. The coords above should take you to the front of the washrooms.
There used to be a yellow sign above the entrance from which some of the answers to the questions were found. Until it is replaced, you can find the answers fairly easily to #2 by looking online, and to replace question #3 tell me the phone number of the payphone inside. Now for your lesson on avalanches!
An avalanche, or snow slide, is simply a mass of snow moving down a slope. Several factors may affect the likelihood of an avalanche, including weather, temperature, slope steepness, slope orientation (whether the slope is facing north or south), wind direction, terrain, vegetation, and general snowpack conditions. Different combinations of these factors can create low, moderate or extreme avalanche conditions.
Avalanches can be surprisingly hard to predict. Changing weather conditions continually affect the strength of the layers within the snowpack, and the snowpack on every slope is different depending on what exposure that slope has to the wind and sun.
In fact, layers within the snowpack are the first thing that avalanche forecasters look at to try to predict the stability of a slope and its potential to slide. Different storms create distinct types and amounts of snow. Once the snow settles onto the existing snowpack, it can quickly metamorphose into distinct crystal types, which are determined both by changes in temperature and whether or not the snow is exposed to the sun.
As the season progresses, the snowpack becomes a multi-layered history of storms and weather. But even a deeply buried layer can continue to change, as changes in temperature slowly move through the snowpack, and heavier snow weighs down on lower layers. A weak layer is created whenever snow crystals are shaped in a way that prevents them from bonding tightly together. This type of snow is called depth hoar. Because of its granular structure, similar to dry sand, depth hoar bonds poorly and creates a very weak layer in the snowpack.
How much of a threat an avalanche may pose depends largely on how deeply buried a weak layer is. When the snow near or on the surface doesn't have much cohesion -- in other words, it's a weak layer -- loose snow slides are common. The snow on the surface begins to slide from a single point, collecting more snow as it moves, and widening out into a triangular shape, creating what is commonly called a sluff. Sluffs are similar to sand rolling down a sand dune. Typically, these loose snow avalanches do not involve much snow and are not a major threat to people or property.
But the threat of larger avalanches increases as a weak layer becomes more and more deeply buried, causing the entire snowpack above to become more unstable. When a weak layer is buried underneath a strong layer, slab avalanches are possible -- if enough stress is added to the slope. Stresses which might trigger a slab avalanche include new or wind-blown snow, a skier or snowmobiler, or an explosive used intentionally for avalanche control.
In a slab avalanche the snow breaks off in a single large plate, which then fractures and moves down the slope. These avalanches tend to be much larger, involve more snow, and are more dangerous to both people and property than sluffs. When people trigger them they are often in the middle of the slab, which is what makes them so deadly; when the avalanche releases, the victim is quickly engulfed in the snow, and the chances for escape are slim.
Ninety percent of all avalanches occur on moderate slopes with an angle of 30° to 45° (snow tends not to accumulate on steeper slopes). The tree line, above which conditions become too harsh for trees to grow, also plays a significant role in avalanche areas. Many avalanches start above the tree line, making high-elevation mountains especially risky. Although forests help stabilize the snowpack, if an avalanche starts above tree line, it can cut its own path, or chute, through the trees below. Likewise, where there is a swath of trees missing from a forested mountainside (and it's not a ski run), there are probably frequent avalanches running down that particular chute. Smooth surfaces, such as a rock face or grassy slope, may cause avalanches during the spring melting season. On the other hand, if the vegetation is very low-lying, such as tree stumps or shrubs, it can become buried underneath the first few snows and be relatively ineffective at anchoring the upper layers of the snowpack.
Avalanches are a significant mountain hazard. Once in motion, snow slides are a powerful force of nature, capable of snapping off mature trees like match sticks, and easily destroying buildings. And when an avalanche finally stops, the snow sets up like concrete, making rescue efforts extremely difficult, and chances for survival slim. “For centuries, mountain dwellers and travelers have had to reckon with the deadly forces of snowy torrents descending with lightning speed down mountainsides. Researchers and experts are making progress in detection, prevention and safety measures, but avalanches still take their deadly toll throughout the world.
Each year, avalanches claim more than 150 lives worldwide, a number that has been increasing over the past few decades. Thousands more are caught in avalanches, partly buried or injured. Everyone from snowmobilers to skiers to highway motorists are caught in the "White Death." Most are fortunate enough to survive. “ (NSIDC Avalanche Awareness)
Avalanche prevention and lessening of their power and destruction” involves a variety of methods. Snow fences are built to prevent the buildup of snow in starting zones, structures are built to stabilize snow. deflecting walls are built to divert avalanche flows away from buildings and even entire towns. Sheds built across roads/highways that pass through persistent avalanche paths can help to protect motorists from avalanches. Additionally, the reforestation of slopes with trees helps to prevent avalanches. Often avalanche control experts actually desire to create smaller, controlled avalanches to prevent larger, uncontrolled ones. Percussion guns, explosives, and even artillery have been used to produce these controlled avalanches when people are kept away. “(about.com)
In order to log this cache you MUST take a photo of yourself with your GPS at the posted coordinates and post it with your log, and then you need to email the owner the answers to the following questions:
1. What is the elevation at the posted coordinates? (Use your GPS!)
2. What are the names of the three closest mountain peaks shown on the sign at the posted coordinates? You will have to now go online to get your answer.
3. Again from the sign, what is not allowed in this area during the winter season and why. ***Note: Oct.2012 someone has advised that the sign is missing. Until it is replaced, you can take a picture of the front of the washrooms showing where the sign was, or give me the phone number of the payphone inside.
4. Name two visible items that are seen and used on the stretch of highway between Hope and the posted coordinates to control and protect us travelers from avalanches.
Remember to post your photo with your log!
Additional Hints
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