Pacific Crest Trail: Northern California. Jeffrey P. Schaffer
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Название: Pacific Crest Trail: Northern California
Автор: Jeffrey P. Schaffer
Издательство: Ingram
Жанр: Книги о Путешествиях
Серия: Pacific Crest Trail
isbn: 9780899977409
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High Altitude Problems
Altitude Sickness
Altitude sickness may occur at elevations of about 8000 feet or more. Symptoms include fatigue, weakness, headache, loss of appetite, nausea, vomiting, and shortness of breath on exertion. Sleep may be difficult for the first night and, if you are above 10,000 feet, perhaps even for one or more additional nights. Regular periods of heavy breathing separated by periods of no breathing at all may awaken the sleeper with a sense of suffocation. Hyperventilation may also occur, causing lightheadedness, dizziness, and tingling of the hands, feet, and mouth. Altitude sickness results from exposure to the oxygen-deficient atmosphere of high elevations. It is aggravated by fatigue and cold. Some people are more susceptible to it than others. As the body adjusts to the lower oxygen pressure, symptoms usually disappear. Resting and drinking extra liquids are recommended. If symptoms persist, descend to lower altitudes.
High-Altitude Pulmonary Edema
However rare, this is a serious and potentially fatal condition. Cases have been reported at altitudes of 8500 feet, but usually it occurs considerably higher. The basic problem, as with altitude sickness, is a reduction of oxygen, and early symptoms are often unrecognized or else confused with altitude sickness. However, in the case of pulmonary edema, reduced oxygen initiates blood diversion from the body shell to the core, causing congestion of the lungs, brain, and other vital organs. Besides exhibiting symptoms similar to those of altitude sickness, the victim is restless, coughs, and eventually brings up frothy, blood-tinged sputum. The only treatment is immediate descent to at least 2000 feet lower and, if available, administration of oxygen. You should secure medical help as soon as possible.
Blood in Urine
If you are at high elevations and exercising to the point of dehydration, you can, like serious long-distance runners, have reddish urine. You are not dying, but this is a good sign that you are overexerting yourself. Slow down.
Ultraviolet Radiation
Above 9000 feet, wear UV-absorbing or reflecting glasses and a hat to protect your eyes, for the dangerous ultraviolet radiation at these elevations is very intense. You can get quite a splitting headache if your eyes get too much radiation. Prolonged exposure to ultraviolet radiation increases your risk of skin cancer, so be liberal with sunscreen on all your exposed skin.
Chapter 3
PCT Natural History
Geology
It is very likely that the California section of the Pacific Crest Trail is unequaled in its diversity of geology. Many mountain trails cross glacial and subglacial landscapes, but which ones also cross arid and semi-arid landscapes? Some parts of your trail will have perennial snow; others are usually dry. Precipitation may be more than 80 inches per year in places, less than 5 inches in others. In each of the three major rock classes—igneous, sedimentary, and metamorphic—you’ll encounter dozens of rock types. Because the PCT provides such a good introduction to a wide spectrum of geology, we have added a liberal dose of geologic description to the basic text. By the end of your journey you’ll have developed a keen eye for rocks and understand the relations between the different rock types. Since we assume that many hikers will have only a minimal background in geology and its terminology, we’ll try to cover this broad subject for them in the next few pages. Those wishing to pursue the subject further should consult the list of references at the end of this book.
Rocks
First, you should get acquainted with the three major rock classes: igneous, sedimentary, and metamorphic.
Igneous rocks
Igneous rocks came into being when the liquid (molten) rock material (magma) solidified. If the material solidified beneath the earth’s surface, the rock is called intrusive, or plutonic, and a body of it is a pluton. If the material reached the surface and erupted as lava or ash, the rock is called extrusive, or volcanic.
Intrusive rocks: The classification of an igneous rock is based on its texture, what minerals are in it, and the relative amounts of each mineral present. Since intrusive rocks cool more slowly than extrusive rocks, their crystals have a longer time to grow. If, in a rock, you can see an abundance of individual crystals, odds are that it is an intrusive rock. These rocks may be classified by crystal size: fine, medium, or coarse-grained, to correspond to average diameters of less than 1 millimeter, 1–5, and greater than 5.
Some igneous rocks are composed of large crystals (phenocrysts) in a matrix of small crystals (groundmass). Such a rock is said to have a porphyritic texture. The Cathedral Peak pluton, which is well exposed on Lembert Dome at the east end of Tuolumne Meadows in Yosemite National Park, has some feldspar phenocrysts over four inches long. High up on the dome these phenocrysts protrude from the less resistant groundmass and provide rock climbers with the holds necessary to ascend the dome.
The common minerals in igneous rocks are quartz, feldspar, biotite, hornblende, pyroxene, and olivine. The first two are light-colored minerals; the rest are dark. Not all are likely to be present in a piece of rock; indeed, quartz and olivine are never found together. Intrusive rocks are grouped according to the percentages of minerals in them. The three common igneous groups are granite, diorite, and gabbro. Granite is rich in quartz and potassium feldspar and usually has only small amounts of biotite. Diorite is poor in quartz and rich in sodium feldspar, and may have three dark minerals. Gabbro, a mafic rock (rich in magnesium and iron), lacks quartz, but is rich in calcium feldspar and pyroxene, and may have pyroxene and olivine. You can subdivide the granite–diorite continuum into granite, quartz monzonite, granodiorite, quartz diorite and diorite. These rocks, which are usually called “granitic rocks” or just plain “granite,” are common in the Sierra Nevada and in most of the other ranges to the south.
Since it is unlikely that you’ll be carrying a polarizing microscope in your backpack, let alone a great deal of mineralogical expertise in your head, your best chance of identifying granitic rocks lies in making educated guesses based upon the following table.
At first you’ll probably estimate too high a percentage of dark minerals, partly because they are more eye-catching and partly because they show through the glassy light minerals. If the intrusive rock is composed entirely of dark minerals (no quartz or feldspar), then it is an ultramafic rock. This rock type, which can be subdivided further, is common along the trail from Interstate 5 at Castle Crags State Park northwest to the Oregon border.
Extrusive rocks: Extrusive, or volcanic, rocks are composed of about the same minerals as intrusive rocks. Rhyolite, andesite, and basalt have approximately the same chemical compositions as granite, diorite, and gabbro, respectively. As with the intrusive rocks, the three volcanics can be subdivided into many groups, so it is possible to find ordinary rocks with intimidating names like “quartz latite porphyry”—which is just a volcanic rock with quartz phenocrysts and a composition in between rhyolite and andesite.