The Dynamic Glaciers of Mount Rainier EarthCache
The Dynamic Glaciers of Mount Rainier
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This Earth Cache encourages you to visit the Paradise Visitors Center at Mount Rainier National Park and to utilize its system of trails to make observations of the Nisqually Glacier and the air temperature in its vicinity. The trails are considered easy and this will require of hike of about 1.6 miles round trip. The elevation is approximately 5400 feet above sea level. You will need to bring a thermometer to take air temperature readings. Stay on the trails at all times.
Warning! Hiking in this area is not recommended from late fall to early summer. Snow storms, poor visibility, and high avalanche danger may create significant hazards. All vehicles, including four-wheel drive, must carry tire chains for travel in the park from November 1 to April 1. Trails in the Paradise area are usually snow free from late July to late October. The Nisqually Glacier is at the head waters of the Nisqually River which flows through west central Washington ultimately into Puget Sound. There are twenty-six (26) Alpine glaciers on Mount Rainier. The glaciers and permanent snowfields cover 36 square miles. Mount Rainier is a great site for scientific investigation and research because it is the most glaciated peak in the continental United States and its close (approximately 50 miles) to Seattle and Tacoma, Washington. The alpine glaciers on Mount Rainier have been under study by the U.S. Geological Survey since 1890's. Alpine glaciers form in stream valleys which are lower than the surrounding terrain and allow the winter snow to accumulate. Snow is eventually compacted into ice and as more snow produces more ice, a glacier is created and it begins to move down valley. The amount it moves depends on how much new ice is formed and how much melting occurs seasonally. As the glacier moves downstream, it will eventually reach a point where the amount of seasonal melting equals the amount of new ice formed, the glacier will cease to move and will be in equilibrium. If the amount of snowfall increases (leading to an increased rate of ice formation) or if the summers become cooler it will once again advance down valley. If the amount of snowfall decreases (leading to a decrease in ice formation) or if the summers become warmer, the glacier will retreat up valley. This means alpine glaciers are sensitive to changes in climate. Since 1850, glaciers worldwide have experienced a fluctuating retreat. The most accessible and most studied glacier on Mount Rainier is the Nisqually. Glacial retreat was identified as early as 1938. Based on the study of its moraines, it has been in retreat steadily since 1976. Retreat rates were highest when summer temperatures were high and winter snowfall was low.) This pattern is identical to the European trend identified in scientific papers published first published in 2001 and confirmed as well in North America in 2005. Interestingly, higher than average snowfall correlates with higher than average mean annual temperatures which confounds our understanding of retreat rates. Theories of atmospheric carbon dioxide based global warming have been widely promoted. The effect of such global warming on alpine glaciers is not well understood. Fortunately we have almost a century of high quality temperature data recorded at the Longmire Ranger Station that can be used to compare current temperatures to see if conditions have changed in significant ways. As a further complication, the Pacific Northwest is subject to a climate variation associated with the Pacific Decadal Oscillation (PDO) which has a negative or cooler phase and a positive or warmer phase. This recently discovered phenomena has a period of about thirty years. Interestingly, the warm phase is characterized by increased snowfall in the Cascades. In addition to temperature and snow fall amount, another factor that could increase glacial ice melts is the presence or absence of dark, silts and sands on the outer surface of the glacier. Because such dark colored materials absorb more energy from sunlight that does a bright white surface of snow, surface coatings of dark silts and sands can increase melting. Such silt and sand deposits can be wind-blown or be the result of rock falls onto the glacial surface. Keep in mind Mount Rainier is primarily andesitic rock that is typically dark gray. To claim this Earth Cache as a find, there are several things you will have to do: 1) Hike to N 46⁰ 47’ 52.13” W 121⁰ 44’ 19.70” using the Paradise trail system. This point is located on the Moraine Trail. 2) Take an air temperature reading. The average high temperature range is 51 to 55 deg F and the low temperature range is 24-27 deg F. Remember, these are average values that include day time highs and night time lows. How you your readings compare? 3) When you observed the Nisqually Glacier, did no notice any dark coatings that could be attributed to fragments and particles of andesite? 4) Describe the flow of water flowing out of the bottom of the glacier. What was its color? Was there significant flow or just a small trickle? 5) Active glaciers grind rock into a fine flour or powder. This gives the water flowing out of the bottom of the glacier a milky color or appearance. Is the Nisqually Glacier an active glacier at this time? 6) Optional: Take a photo of yourself with Mount Rainier in the background and post to geochache.com. Send me the answers/observations associated with tasks 2-5 via email; then post your find!
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