Sierra South. Mike White
Читать онлайн книгу.
left behind. The ubiquitous lodgepole pine begins to make her appearance, and will provide shade and company along the remainder of the trek. The route traces the natural curve along the north side of the canyon and follows this contour as it curves east.
After crossing a ridge, the trail turns back toward Bear Creek and heads down the hill, leveling off after reaching the creek. Well-used campsites begin to appear along the banks of the water. As you continue east, Old Kip Camp appears after a wet, muddy area. Just beyond is the junction with the PCT/JMT (8975´; 11S 332792 4137402).
Turn right on the PCT/JMT, now heading south. This section of trail parallels Bear Creek, running at the bottom of the canyon, for the next mile. Several granite slabs rise from the rushing water, providing relaxing lunch spots along the banks. The path jogs west briefly before entering a narrow section of canyon, and then it levels off while heading away from the creek.
Soon after the trail levels, reach the Italy Pass Trail junction (11S 333831 4134908). Here, this trip turns left (east), leaving PCT/JMT and heads east up open granite slabs. The trail may be faint here, but it becomes quite definite under the trees. Pass a drift fence and a welcome sign announcing that Hilgard Meadow is closed to grazing. From here, the trail threads gently under lodgepole pine for an easy mile to reach the grassy expanses of Hilgard Meadow (9600´). Mt. Hilgard looms almost 4000 feet above, and the meadow underfoot supports thousands of purple Indian paintbrush plants in mid-season. Excellent campsites border the northwest side of this subalpine meadow.
Skirting the north side of Hilgard Meadow, the trail stays near Hilgard Branch as it climbs moderately over slabs and crosses the outlet of Hilgard Lake before passing another drift fence. The path then rapidly crosses several small creeks before leaving tree cover behind. Here, the route may become faint as it climbs away from Hilgard Branch and crosses an open, rocky slope. The path then passes through a wet meadow and becomes indistinct. Descend slightly before meeting the edge of the forest, where the trail becomes more obvious and resumes climbing. The track passes a nice campsite near the main creek before crossing another spring-fed rill.
Now far from the main creek, the trail climbs up steep slabs, following the curve in the canyon as it turns east, steepens, and narrows. Downstream, the canyon is wide and gently sloping, and beyond the narrow gorge, the canyon floor again becomes a meadow, wide and gently sloping. This variation in form is due to differences in the structure of the bedrock.
EFFECTS OF GLACIAL EROSION
Although stream erosion did most of the difficult work to carve this canyon, glaciers have also modified its shape. Before glaciers come, stream canyons usually have a V-shaped cross-section. After the passing of glaciers, the canyons usually have a pronounced U-shaped cross section.
Glaciers, then, tend to do most of their erosion horizontally for several reasons. Primarily, Sierra glaciers are wet based: They ride along on a thin layer of water between the ice and the rock. (Water occurs there due to heat and pressure trapped under the heavy, insulating river of ice.) With this kind of lubrication, the ice tends to slide over, rather than dig deeply into, the bedrock. However, out at the margins of the glacier, colder air and thinner ice allow the glacier to freeze to the ground. Being “glued” to the sides of the valley, the passing glacier tears out pieces of bedrock and carries them away. This action is called glacial quarrying.
In order to account for the variations in canyon slope and width, you can look at how erosion reflects bedrock structure. In this canyon, the primary variable of structure is joints—cracks in the bedrock. Since joints are planes of weakness, then the more there are, the faster the rock is weathered (broken down) and carried away.
Where joints are mostly oriented vertically, glaciers break off column-like pieces from the valley sides, thereby undermining the canyon walls above. In such a place, the valley will be exceptionally flat-bottomed and steep-sided, like Yosemite Valley.
Конец ознакомительного фрагмента.
Текст предоставлен ООО «ЛитРес».
Прочитайте эту книгу целиком, купив полную легальную версию на ЛитРес.
Безопасно оплатить книгу можно банковской картой Visa, MasterCard, Maestro, со счета мобильного телефона, с платежного терминала, в салоне МТС или Связной, через PayPal, WebMoney, Яндекс.Деньги, QIWI Кошелек, бонусными картами или другим удобным Вам способом.