One Best Hike: Yosemite's Half Dome. Rick Deutsch
Чтение книги онлайн.
Читать онлайн книгу One Best Hike: Yosemite's Half Dome - Rick Deutsch страница 4
Название: One Best Hike: Yosemite's Half Dome
Автор: Rick Deutsch
Издательство: Ingram
Жанр: Книги о Путешествиях
Серия: One Best Hike
isbn: 9780899976969
isbn:
The hike can be done in one day, or more leisurely in two if time permits. This guidebook describes the most popular day route to the summit. Regardless of your strategy, it will help you prepare prior to leaving home and then help steer you up the mountain on your summit day. My intent is to provide a resource that can enable nearly any physically able person to complete the hike. Further, I believe that this educational guide will enhance visitor understanding and enjoyment of park resources.
I first hiked Half Dome in 1990 and was so moved by the experience that I decided to do it annually. My motivation goes back to the sixth-century tale of Milo of Croton (it was a Greek colony in southern Italy). As a boy, Milo would pick up a small calf on a daily basis. As the calf grew larger, Milo continued to lift the animal, and the boy became stronger. His muscles became so powerful that he could carry the calf with ease when it became a full-size ox. This constant yet gradual training resulted in Milo developing into a man of incredible strength, so much so that he won the ancient Olympic wrestling title a remarkable six consecutive times. He was likely an actual historical person, as he is mentioned by many classical authors, among them Aristotle. Perhaps this is a poor analogy, but maybe by working out on a regular basis and staying in condition for this hike, I will live a few years longer than the actuarial tables project.
While on these hikes, I have noticed many unprepared optimists setting out, knowing little of what lies ahead. Their poor preparation was obvious. I have seen many people suffer from a lack of water, sore muscles, inferior shoes, and a big underestimation of the magnitude of the hike. And yet, I’ve found no other Half Dome–specific hiking guides. You’ll find many general hiking in Yosemite guidebooks, but they cover Half Dome in only a few pages. This guide should fill your knowledge gaps and allow you to hit the trail with confidence.
Welcome to Yosemite!
This book was designed to be small and fit into your pack, so take it on your hike. Many people will be on the trail—you won’t get lost. I’ve included photos of most of the trail, so you won’t wonder what’s in store. Although these pictures show the high points of the hike, nothing will replace seeing these majestic sights yourself. I also include many historical vignettes of events that occurred during the evolution of Yosemite. Finally, all opinions and suggestions are mine. Others may approach these topics differently or disagree with me. Pick out what you like and make informed decisions.
Geology of Yosemite and Half Dome
When we try to pick out anything by itself, we find it hitched to everything else in the Universe.
—John Muir
How Yosemite Was Formed
Yosemite’s grandeur began about 500 million years ago, when the entire region was an ancient seabed. Since the beginning, the plates that make up the outer portion of the Earth have been moving—coming together and breaking apart. Witness how nicely eastern South America fits into western Africa. About 100 million years ago, the plate west of today’s California, called the Pacific plate, dove eastward under the North American plate, causing the uplift of the region. The mountains still rise today at a rate of 1 foot every 1,000 years. Deep below the ground, constant Earth movement and the effects of pressure and heat created magma, which gradually rose toward the surface. When the magma found boundaries or rifts between the surface plates (subduction zones), it rose up to erupt as volcanoes. This is a phenomenon that happens regularly on Earth. However, sometimes the hot 2,000-degree magma has no route to the surface. It rises but then is forced to lie a few miles below the surface and slowly cool under intense pressure. It then crystallizes into a pluton of granite. When many of these plutons come together, they become batholiths. There are many types of granite, but most consist of a chemical mixture of hornblende, mica, feldspar, quartz, and other minerals. Its classic look is a salt-and-pepper gray, but the color can vary. It can have different patterns and lines due to intrusions during its formation.
In California, as the Pacific plate slowly crawled under the North American plate, the subduction zone got extremely hot and melted some of the plate, along with some of the overlying crust. Because of the temperature difference with the rocks around it, the magma rose and formed the Sierra granite directly from this subducting slab. This huge mass would later become the underlay of the Sierra Nevada mountains. Most of Yosemite’s granites were formed 85–150 million years ago. Add to the recipe the millions of years of erosion caused by snow, rain, and wind, and gradually the batholiths were exposed. One result was the 80-by-400-mile granite bedrock of the Sierra Nevada.
The best reader-friendly book on Yosemite’s formation is Geology Underfoot in Yosemite National Park. It was cowritten by Allen F. Glazner, professor of geological sciences at the University of North Carolina, and ranger Greg Stock, the first-ever park geologist at Yosemite. The advances in technology, such as optical remote sensing, high-resolution photography, seismic monitoring, and rockfall runout simulations, are now part of the park’s tools to study rockfalls.
From about 10–3 million years ago, the Merced and Tuolumne rivers carved down deep into the land with greater intensity. The uplifted land gave more gravitational power to the river. The eroded earth gradually found its way into the Central Valley.
Uplift and river erosion
Then, from about 3 million to 18,000 years ago, global cooling resulted in three major glacial periods. Glaciers are simply large masses of snow and ice that do not melt. The snow and ice filled in valleys and accumulated thousands of feet high. Gravity allowed them to slowly advance. As the lower layer of ice picked up rocks, it carved the path of the glacier. The representation below reflects geologists’ belief that Half Dome and many other high peaks were above the glaciers. We will discuss the geologic formation of Half Dome in the next section.
Early glaciation
Recent glaciation
The last major glacier retreated from Yosemite about 18,000 years ago. (We still have two glaciers: Mount Lyell and Mount Maclure.) The classic U shape of glacially carved valleys is not readily evident in Yosemite Valley because research has shown that the bedrock lies about 2,000 feet below today’s roads. How did that happen? During its time, the last glacier slowly covered the area between El Capitan and Bridalveil Fall. As it dug deep, stone and debris were deposited in front of it. When it finally melted and retreated back to the east, the terminal moraine created an earthen dam. The dam stopped the waters from the melting ice and created a lake that geologists call Yosemite Lake. By 10,000 years ago, the lake had filled with sediment, disguising the U shape. Scientists believe the U shape is still there—it’s just 2,000 feet below the surface.