Technical information, news, research, and opinion on avalanches, snow safety, and winter backcountry travel.

Friday, February 5, 2010

How Much Do You Know About Avalanches?

She moves in mysterious ways—U2

NOTE: I hope that my bi-monthly post schedule of late isn't boring. Most of these posts require serious thinking, writing, and editing. I also have to vet the material in the posts with actual humans, and sometimes seek professional input. Several of the posts from earlier this year required 30-40 hours of writing time, which is significant for a blog. It's also important to mention that I strive to write posts that advance people's understanding rather than simply regurgitating popular information.

Are you ready to test your knowledge of avalanches?

Most of the following questions are drawn from the material contained in The Avalanche Handbook. It may be useful to determine how many questions you can answer before taking the time to complete this exam. In that case, simply print this post and circle all the questions you can answer. Then, count the number of questions and grade yourself. Anyone who can complete this exam can consider themselves highly knowledgeable, but an inability to complete the exam doesn't mean that you're ignorant. So please take this with a grain of salt.

In case you think an exam with 300 questions is a bit excessive, you might be interested to know that this exam does not include about 500 other important questions about mountain weather, crystal formation, snow metamorphism, avalanche terrain, avalanche formation, and avalanche dynamics.

If this exam serves no other purpose, it should at least convince you of the massive depth of avalanche science.

Feel free to get on my case about any "bad" questions. ( Here are the answers. )

The Exam
  1. Describe Ian Burton's rule of thumb for natural disasters.
  2. Does this rule of thumb apply to avalanches in Western North America? Explain your answer.
  3. What is the Earth's weakest surficial material?
  4. What is the ratio of air/ice commonly found in avalanches?
  5. Alpine snow is typically found within how many degrees of its melting point?
  6. Significant avalanche research started in what country and in what year?
  7. Describe how equipment modifies human behaviour.
  8. What percentage of backcountry travelers trigger the avalanche themselves?
  9. What does this suggest about the root cause of these fatalities?
  10. Name three major components of risk?
  11. What causes most destructive avalanche cycles?
  12. List three snow climates found in North America and briefly describe each.
  13. Minor changes in slope angle have a significant affect on the character and areal distribution of wind deposited snow. True or False?
  14. Can avalanches occur from loading when snow is not falling from the clouds?
  15. Heat transfer in alpine snow is very rapid. True or False?
  16. List the two key types of radiation that affect snow surface temperature.
  17. Variations in snow crystal type are responsible for some avalanches. True or False?
  18. Provide the common definition for surface hoar.
  19. Describe the process by which surface hoar forms.
  20. Provide the common definition for facets.
  21. Describe the process by which facets form.
  22. What is the relationship between trees and snowpack metamorphism?
  23. Describe snow grain types often found near rocks.
  24. Why do these grain types form near rocks?
  25. List three types of ground cover anchors.
  26. What serves as the upper and lower boundaries for winter snowpack?
  27. Which boundary is usually cooler?
  28. Once deposited on the ground, how many minutes must pass before snow crystals begin to change form?
  29. Why do these initial changes cause direct-action, loose-snow avalanches?
  30. Why do crystals change form?
  31. What snowpack-related force rearranges grains in the snowpack?
  32. Growth rate and crystal form are more dependent on pore size than temperature gradient. True or False?
  33. Faceted forms and highly angular snowflakes develop because of similarities between vapor saturation conditions in the atmosphere and snowpack. True or False?
  34. Why does depth hoar only form near the ground? Be very specific.
  35. How does a crust influence crystal formation?
  36. What leads to dry/wet faceting?
  37. If avalanches released easily on depth hoar, what conclusion could be drawn about travel in continental climates?
  38. Who coined the term "persistent forms"?
  39. What are the characteristics of the persistent forms?
  40. Discuss human perception with respect to persistent forms.
  41. Name the two most general classifications of avalanches.
  42. What is the normal range of slope angles for slab avalanche release?
  43. Triggering is possible during travel over flat terrain. True or False?
  44. What is the minimum thickness required to bury a skier?
  45. Skier triggering of slabs thicker than ________ is rare.
  46. Define the two basic situations in operational avalanche forecasting.
  47. Define the basic rule of route selection.
  48. Recent tracks indicate stability and safety because the slope has already been tested. True or False.
  49. Around what element is modern avalanche forecasting framed? From what perspective are forecasts issued?
  50. List all seven elements of applied avalanche forecasting.
  51. Avalanche forecasting is a ________ problem.
  52. All seven elements are ________.
  53. Most avalanche accidents occur as a result of human errors. True or False.
  54. Provide the definition of forecasting.
  55. Define the root cause of most avalanche accidents.
  56. How is avalanche forecasting linked to risk analysis?
  57. Is avalanche forecasting limited only to estimates of instability? Explain why or why not.
  58. Define the major physical uncertainty with respect to avalanche forecasting.
  59. Avalanche forecasting is defined in terms of ________.
  60. Whereas traditionally, avalanche forecasting was defined in terms of ________.
  61. In avalanche forecasting, what type of information is most highly prized?
  62. To what does triggering level refer?
  63. Provide three examples of types of forecasting relative to triggers.
  64. How do most slab avalanches release?
  65. Upon what does the energy required to release a slab avalanche depend?
  66. What is the primary reason avalanche forecasting is probabilistic, with a risk-based character?
  67. Define the goal of avalanche forecasting. Discuss the primary sources of uncertainty.
  68. State the goal of avalanche forecasting from the human perspective.
  69. How is this goal accomplished?
  70. Define relevant information in the context of avalanche forecasting.
  71. There is a strong link between quantity of information and accuracy of decisions. True or False.
  72. There is a strong link between confidence in a decision and the resulting accuracy. True or False.
  73. Briefly discuss the role of redundant information in statistical predictions.
  74. List and describe each data classification used in operational avalanche forecasting.
  75. Discuss ensemble forecasts.
  76. Discuss the scale of failure in human perception with respect to avalanches.
  77. Define perception.
  78. Discuss the two general components of human influences.
  79. What relationships does the Risk-Decision Matrix display?
  80. Define Operational Risk Band [ ORB ].
  81. What is the upper boundary of the ORB?
  82. What is the lower boundary of the ORB?
  83. Provide a list of Type I errors.
  84. Provide a list of Type II errors.
  85. Define target risk.
  86. What are the consequences of Type I errors.
  87. What are the consequences of Type II errors.
  88. What is the relationship between uncertainty and perception?
  89. Who coined the term risk homeostasis?
  90. Explain risk homeostasis and provide an example.
  91. List two or three items that improve perception.
  92. List two or three items that degrade perception.
  93. When might biases have a small effect on perception of instability?
  94. When might biases have a large effect on perception of instability?
  95. Discuss absolute instability relative to perception.
  96. Discuss conditional instability relative to perception.
  97. Write a brief explanation of the implications of perception of instability and the public danger scale.
  98. Draw the continuum of instability and describe perception at three points.
  99. Why is the link between data sampling and perception so important?
  100. What does White ( 1974 ) argue about perception of hazard?
  101. What is shown by statistics that compare fatalities to the public danger scale?
  102. Why is perception better for instability in new snow?
  103. Is randomness desired in the sampling process for avalanche forecasting?
  104. Why are slopeside instability tests sometimes compared to playing the lottery?
  105. Describe the two main types of reasoning used in avalanche forecasting.
  106. Provide an example of each type of reasoning.
  107. Information for avalanche forecasting consists of two types. Explain each and include examples.
  108. Should one always have an opinion about instability before attempting risky activities in avalanche terrain?
  109. If avalanche forecasting is Bayesian, what information type constitutes the prior?
  110. If avalanche forecasting is Bayesian, what information type constitutes the likelihood?
  111. If avalanche forecasting is Bayesian, what information type constitutes the posterior?
  112. Define informational entropy.
  113. Why are data such as wind speed and direct data harder to interpret than cracking of the snow cover?
  114. Define highly correlated.
  115. What is necessary for dealing with highly correlated data?
  116. Does the class of information ( I, II, III ) always give the most priority to Class I information?
  117. Describe the theory of weighting data.
  118. Define spatial scale relative to avalanche forecasting.
  119. Define temporal scale relative to avalanche forecasting.
  120. Define scale-matching.
  121. Provide an example of what might happen if scale-matching is not performed.
  122. Explain the three primary spatial scales.
  123. Difficulty of forecasting is inversely proportional to scale. True or False.
  124. If true, explain. If false, explain.
  125. Does failure to perform scale-matching result in many needless accidents?
  126. Define nowcast.
  127. Which is more difficult: forecasting stability for next Wednesday or next Thursday?
  128. Why does chaos influence avalanche forecasting?
  129. Discuss "search for supportive evidence" and how to neutralize this bias.
  130. Discuss "inconsistency" and how to neutralize this bias.
  131. Discuss "conservatism" and how to neutralize this bias.
  132. Discuss "recency" and how to neutralize this bias.
  133. Discuss "frequency" and how to neutralize this bias.
  134. Discuss "availability" and how to neutralize this bias.
  135. Discuss "illusory correlations" and how to neutralize this bias.
  136. Discuss "selective perception" and how to neutralize this bias.
  137. Discuss "expert halo" and how to neutralize this bias.
  138. Discuss "underestimating uncertainty" and how to neutralize this bias.
  139. Discuss "excessive optimism" and how to neutralize this bias.
  140. Discuss "anchoring" and how to neutralize this bias.
  141. Discuss "rules of thumb" and how to neutralize this bias.
  142. Discuss "guide-client relationship" and how to neutralize this bias.
  143. Discuss "social proof" and how to neutralize this bias.
  144. Explain asymmetry of use relative to classes of information.
  145. Why does sampling performed on "average areas" lead to dangerous conclusions?
  146. Explain Class I Factors.
  147. Explain Class II Factors.
  148. Explain Class III Factors.
  149. Abundance of information is needed to ________ ________ ________.
  150. List at least four factors that contribute to uncertainty.
  151. What is needed with high uncertainty?
  152. Why is screening Class III data especially important?
  153. Which observations have priority?
  154. List one very reliable indicator of unstable snow.
  155. Define indicator slope.
  156. Discuss the benefits and drawbacks of using indicator slopes to evaluate instability.
  157. What is indicated by avalanche activity on indicator slopes?
  158. Provide a basic procedure for collecting data about avalanche occurrences.
  159. Discuss the benefits and drawbacks of using devices to monitor avalanche activity.
  160. Why keep records of avalanche activity?
  161. Define fracture propagation.
  162. What causes fracture propagation?
  163. Is fracture propagation the same as settling?
  164. When might fracture propagation occur on a low-angle slope?
  165. Is subsidence of the snowpack always noticeable when a fracture propagates?
  166. Does fracture propagation help reduce uncertainty?
  167. Define crack propagation.
  168. Does crack propagation help reduce uncertainty?
  169. Define instability test.
  170. What is the purpose of an instability test?
  171. An instability test provides what information? Be specific.
  172. What do the results of an instability test tell you about the snowpack in the surrounding area?
  173. Instability tests serve as Class I information if instability is revealed. True or False.
  174. If true, explain. If false, explain
  175. Why might an instability test fail to reveal instability?
  176. What is the generally accepted minimum slope angle for an instability test?
  177. Does the size of the test area affect the results? Explain.
  178. Explosives test the largest area of the snowpack. True or False.
  179. Which is better: a single, detailed test or many tests with less detail?
  180. Explain your answer to the previous question.
  181. Define test skiing.
  182. Where does test skiing usually take place?
  183. When is test skiing avoided?
  184. Define ski stabilization.
  185. What is another term for ski stabilization?
  186. List general guidelines for test skiing?
  187. What does avalanche release by explosives indicate about instability?
  188. How to you perform a Rutschblock test?
  189. List and define the load levels for Rutschblock test.
  190. What is the principle difficulty with a Rutschblock test?
  191. Is the Rutschblock test reliable for weak layers deeper than 1 meter?
  192. How do you perform a compression test?
  193. List and define the load levels for compression test.
  194. What is the principle difficulty with the compression test?
  195. Is the compression test reliable for weak layers deeper than 1 meter?
  196. Explain why or why not.
  197. How do you perform an extended column test?
  198. List and define the test results for the extended column test.
  199. Discuss false positives relative to the extended column test.
  200. Is the extended column test reliable for weak layers deeper than 1 meter?
  201. Explain why or why not.
  202. When are results of instability tests regarded as Class I information?
  203. Discuss fracture character.
  204. The shear quality scale is a measure of what data quality?
  205. Explain each level of shear quality.
  206. Relative to the state of snowpack instability, what are three possible outcomes of a past avalanche?
  207. Why monitor snowpack depth?
  208. What is a basic requirement for avalanches?
  209. Describe a typical scenario for avalanche formation early in the season.
  210. How do you measure shallow snow?
  211. How do you measure deep snow?
  212. What is threshold snow depth?
  213. Slopes disturbed by human activity contain snow different from most backcountry slopes. True or False.
  214. Define surface penetrability?
  215. Why evaluate surface penetrability?
  216. What is indicated by deep ski penetration?
  217. What is indicated by lower-than-average ski penetration?
  218. Relative to instability, discuss the positive and negative aspects of increases in temperature?
  219. Relative to instability, discuss the positive and negative aspects of decreases in temperature?
  220. What is the relationship between temperature and fracture toughness of the weak layer?
  221. What is the observation technique for measuring snow temperature?
  222. How do you calibrate a thermometer?
  223. Provide four general examples of snow-temperature influence for the following ranges: <5° C, -1° to -5° C, -1° to 0° C, isothermal.
  224. What is the major difficulty in evaluating wet-snow stability?
  225. What measurement can accurately predict a full-depth avalanche?
  226. What are six important questions for evaluating snowpack structure?
  227. Define full snow profile.
  228. What is the purpose of a test profile?
  229. The primary advantage of a test profile, compared to a full study, is increased number of observations. True or False.
  230. Describe the type of information typically sought by a test profile?
  231. A single detailed profile is more valuable than many quick profiles? True or False.
  232. List several criteria for choosing the site of a test profile?
  233. How do you weigh the information gained from a test profile?
  234. What Class I information can be learned from a test profile?
  235. What Class II information can be learned from a test profile?
  236. Provide the correct sequence of events for evaluating instability at a test profile.
  237. Discuss the correct procedure for probing the snowpack with a ski pole or probe?
  238. What is the most important observation with respect to the snowpack?
  239. What are the five key observations used to estimate shear strength of weak layers and interfaces?
  240. Describe each observation.
  241. Discuss surface condition relative to bonding of new snow.
  242. Bonding over rough surfaces is usually ________.
  243. Bonding over smooth surfaces is usually ________.
  244. What is a temperature mismatch?
  245. List three qualities that promote bond formation.
  246. List three qualities that limit bond formation.
  247. Provide three examples of snow types for which poor bond formation is expected.
  248. Define snow water equivalent.
  249. Provide the equation for determining snow water equivalence.
  250. Why is density of snow useful in forecasting avalanches?
  251. What is the range of optimal densities for slab avalanche formation?
  252. Which is more important: rate of precipitation or water equivalance?
  253. Explain the answer to the previous question.
  254. Discuss the relationship between precipitation intensity, rate of precipitation, and shear stress.
  255. Why are rules of thumb with respect to rate and intensity of precipitation often of little use?
  256. Relative to the manner in which snow fails, why is precipitation intensity important?
  257. Define settlement.
  258. How is settlement related to strength increases?
  259. Why do high rates of settlement sometimes imply increased chance of avalanching?
  260. Provide the equation for determining settlement.
  261. What is the threshold speed for wind transport ( dry snow )?
  262. At what speed is snow most efficiently transported into avalanche starting zones?
  263. What happens to snow when wind speeds are greater than 25m/second?
  264. What wind variable determines the aspects that are most favorable for avalanching?
  265. Are direct observations of localized wind characteristics observable at the synoptic scale?
  266. Information about the direction and speed of are usually acquired by what equipment?
  267. How can you observe wind characteristics without relying on equipment?
  268. Good snow stability analysts watch for signs of drifting while driving. True or False.
  269. Ripples on the snow surface run ________ to the wind.
  270. Sastrugi point in the ________ of the wind.
  271. Cornices face ________.
  272. Scour holes appear on the ________ side of trees, rocks, and posts.
  273. Why is the relationship between blowing snow and avalanche formation hard to quantify?
  274. Air temperature influences which aspects of instability?
  275. Temperature trends during storms are important. True or False.
  276. Rising air temperatures during a storm have what effect?
  277. Avalanching sometimes starts immediately when air temperature reaches 0°. True or False.
  278. Prolonged warming often induces what type of avalanche?
  279. Why are these avalanches difficult to forecast?
  280. List two or three instruments used to measure air temperature.
  281. What is the relationship between high humidity and wind-transported snow?
  282. List another affect of high humidity related to wind-transported snow.
  283. What is the dominant influence on snow temperatures in the spring?
  284. Is there a lapse between solar radiation input and free water production inside the snowpack?
  285. Discuss radiation relative to dense cloud cover.
  286. Discuss radiation relative to thin cloud cover.
  287. The snow in cirques and gullies receives more heat than open slopes. True or False.
  288. Please explain the answer to the previous question.
  289. Discuss the character of Class I, Class II, and Class III factors.
  290. In what order are these factors observed to produce a synoptic scale forecast?
  291. In what order are these factors observed to produce a micro scale forecast?
  292. Which forecast type is of the most interest to backcountry users?
  293. Explain your answer to the previous question.
  294. Briefly describe conventional avalanche forecasting.
  295. 80% of avalanche fatalities occur during what general activity?
  296. Forecasting and hazard evaluation are only part of the picture. True or False.
  297. What is the major difference between "office-based" avalanche forecasting and backcountry avalanche forecasting?
  298. What is a stability rating?
  299. What is a hazard rating?
  300. Which is more useful during backcountry travel, a hazard rating or stability rating?
  301. Explain your answer to the previous question.
  302. Low. { Write the danger scale description. }
  303. Moderate. { Write the danger scale description. }
  304. Considerable. { Write the danger scale description. }
  305. High. { Write the danger scale description. }
  306. Extreme. { Write the danger scale description. }
  307. Very Good Stability. { Write the appropriate description. }
  308. Good Stability. { Write the appropriate description. }
  309. Fair Stability. { Write the appropriate description. }
  310. Poor Stability. { Write the appropriate description. }
  311. Very Poor Stability. { Write the appropriate description. }

A = 277 points
B = 245 points
C = 214 points
D = 185 points
F = Less than 185 points

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