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Mount Shasta is a 14,179 foot stratovolcano located in Siskiyou County in northern California. It has an estimated volume of 108 cubic miles, making it the most voluminous stratovolcano in the Cascades. It is the fifth highest peak in California.
Physically unconnected to any nearby mountain, and rising abruptly from miles of level ground which encircles it, Mount Shasta stands some 10,000 feet above the surrounding area. The mountain consists of four overlapping volcanic cones which have built a complex shape, including the main summit and the prominent satellite cone of 12,330 feet Shastina which has a visibly conical form. Mount Shasta's surface is relatively free of deep glacial erosion, except for its south side where Sergeants Ridge runs parallel to the U-shaped Avalanche Gulch. This is the largest glacial valley on the volcano, although it does not presently have a glacier in it.
There are seven named glaciers on Shasta, with the four largest (Whitney, Bolam, Hotlum, and Wintun) radiating down from high on the main summit cone to below 10,000 feet primarily on the north and east sides. The Whitney Glacier (the first glacier in the continental U.S. discovered and named)is the longest and the Hotlum is the most voluminous glacier in the state of California. Three of the smaller named glaciers occupy cirques near and above 11,000 feet on the south and southeast sides, including the Watkins, Konwakiton, and Mud Creek Glaciers.
During the last 10,000 years Shasta has erupted an average of every 800 years, but in the past 4,500 years the volcano has erupted an average of every 600 years. The last significant eruption on Shasta occurred about 200 years ago.
Mount Shasta can release volcanic ash,and pyroclastic flows of dacite and andesite lava. Its deposits can be detected under nearby small towns totalling 20,000 in population. Shasta has an explosive, eruptive history. There are fumaroles on the mountain, which show that Shasta is still alive.
The worst case scenario for an eruption is a large pyroclastic flow, such as what occurred in the 1980 eruption of Mount St. Helens. Since there is ice, such as Whitney Glacier and Mud Creek Glacier, lahars would also result. Ash would probably blow inland, perhaps as far as eastern Nevada. There is a small chance that an eruption could also be bigger, resulting in a collapse of the mountain, as happened at Mount Mazama in Oregon, but this is of much lower probability. The U.S. Geological Survey considers Shasta a dormant volcano, which will erupt again sometime within the next several hundred years.
To log this cache, park during daylight hours at the rest stop on I-5 which is located five or six miles NW of the town of Weed, either northbound (N 41 28.631 W 122 27.289) or southbound (N 41 28.662 W 122 27.401). Take a picture of yourself (or someone in your party)holding a GPS with Mount Shasta in the background. Then e-mail me the answers to the following questions (do NOT post the answers on your log):
1. How far up the mountain is the snow line?, and the tree line?
2. Describe the clouds that are on or near the mountain.
3. What three types of volcanos are in the Shasta area? Which type is Mount Shasta?
4. Black Butte, which is visible about ten miles southwest of Mount Shasta, is what type of mountain?
5. How many long-needle pine trees are in the rest area where you are parked?
Additional Hints
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