As skiers hit the slopes this winter, EARTH Magazine explores the science of how to keep them and other winter explorers safe. Every year, hundreds of people are killed by avalanches. Understanding the science of the frozen environment is only part of this story; communicating the risk is a field as dynamic as the weather systems and terrains that foster avalanches.
Nowhere else in the United States are avalanches more deadly than in Colorado. The reason can be found in the Colorado snowpack. Located furthest from the oceans, the Colorado mountains usually have a shallower and colder snowpack than other western states. And in cold, shallow snowpacks there are physical processes at work making them more avalanche prone (see Snowpack Factors). The mountains west of Colorado (e.g., Utah's Wasatch, California's Sierras, and Washington's Cascades) see numerous and large avalanches during storms but few avalanches between storms. That's because the deep, dense snowpack becomes very strong after storms end. That is not true in Colorado, where the cold, shallow snowpack is much slower to gain strength, and can sometimes lose strength, in the clear weather between storms.
Each winter the Maine Geological Survey participates in a survey to monitor Maine's snowpack. On schedule, staff of the Maine Geological Survey visit specific sites across the State to measure the depth and water content of the snow on the ground. The sites have been carefully selected according to their slope, tree cover, and exposure to wind and sun direction so that they are free of local effects such as drifting and excessive melting.
Today's winter storm expected to impact the Mid-Atlantic is being described as "historic." But really, how do we know? Is just the total amount of snow important, or is it how it affects people? EARTH Magazine Online takes a special look at NOAA's efforts to categorize snowstorms - similar to the rankings of other natural disasters - and to measure their effects on society.