The Explorer's Guide to Death Valley National Park, Third Edition
496
The Explorer's Guide to Death Valley National Park, Third Edition
496eBook
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Overview
Originally published in 1995, soon after Death Valley National Park became the fifty-third park in the U.S. park system, The Explorer's Guide to Death Valley National Park was the first complete guidebook available for this spectacular area.
Now in its third edition, this is still the only book that includes all aspects of the park. Much more than just a guidebook, it covers the park's cultural history, botany and zoology, hiking and biking opportunities, and more. Information is provided for all of Death Valley's visitors, from first-time travelers just learning about the area to those who are returning for in-depth explorations.
The book includes updated point-to-point logs for every road within and around the park, as well as more accurate map than those in any other publication. With extensive input from National Park Service resource management, law enforcement, and interpretive personnel, as well as a thorough bibliography for suggested reading, The Explorer's Guide to Death Valley National Park, Third Edition is the most up-to-date, accurate, and comprehensive guide available for this national treasure.
Product Details
| ISBN-13: | 9781607323419 |
|---|---|
| Publisher: | University Press of Colorado |
| Publication date: | 01/15/2015 |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| Pages: | 496 |
| File size: | 25 MB |
| Note: | This product may take a few minutes to download. |
About the Author
Read an Excerpt
The Explorer's Guide to Death Valley National Park
By T. Scott Bryan, Betty Tucker-Bryan
University Press of Colorado
Copyright © 2014 University Press of ColoradoAll rights reserved.
ISBN: 978-1-60732-341-9
CHAPTER 1
Geologic History
THE SETTING
Death Valley National Park has an extraordinarily long and complex geologic history. Its most ancient rocks are more than 1.8 billion years old, whereas its youngest are forming today. They have been folded, faulted, and recrystallized in every imaginable way, inundated by volcanic lava and ash beds, and deeply sliced by erosion. The result is a wonderland that represents both the driest part of the Great Basin and the most extreme portion of the Basin and Range.
The Great Basin is a geographic region that covers parts of Oregon, Idaho, Wyoming, Utah, Nevada, and California. It is defined by its climate and hydrology. Heavy rain and snow may fall in the mountains, but the intervening valleys are dry because of the storm-blocking "rain shadow" effect of its mountain ranges. Streams draining the slopes simply soak into the ground or evaporate. None of the rivers reaches the ocean. In the spring and early summer there is sometimes enough runoff to form small lakes on the valley floors, but they soon dry up in the summer heat, leaving behind shimmering playas — barren lake beds of salt and clay.
The Basin and Range is the geologic province that formed the Great Basin's mountains. The crust of the earth was uplifted and stretched under severe tension, and large-scale fault zones broke it into a series of parallel north-south-trending valleys and ranges that march east one after another from the Sierra Nevada Mountains in California to central Utah, north into Idaho and Wyoming, and south through Arizona into Mexico.
The Basin and Range is geologically young — less than 65 million years old. Its development began in Utah. As time went on the action gradually migrated westward and produced greater relief. Because it is nearly westernmost in the province, the Death Valley region boasts some of the youngest and most extreme topography of all the Basin and Range. Its mountains are still growing taller, and the valleys are becoming deeper. Rock exposures are fresh and reveal nearly every variety of stone that exists. The rocks in one mountain range are often completely different from those a few miles away, and sometimes the age difference can vary a billion years in only a few inches. Great earthquakes and volcanic eruptions have torn the surface. Ice Age lakes filled the valleys with hundreds of feet of water and left behind wave-cut terraces, beaches, and salt beds. Wind has stripped the surface bare in some places and piled up sand dunes in others. The result is a geological paradise.
What we see today is only the latest development in a region that contains many complex ingredients that have gone through countless processes. A little understanding about rocks and time helps make sense of Death Valley National Park's otherwise incomprehensible hodgepodge of geology.
PRECAMBRIAN TIME
Geologic time is divided into four major parts based mostly on the types of life that existed during each era. The fossil record indicates that life had somehow developed on Earth nearly 3.5 billion years ago, but from then through most of the next 3 billion years there was little change. Life existed entirely as single-celled forms such as archaea, bacteria, and cyanobacteria. These cells reproduce by simple cell division, and there is little evolution because the offspring is genetically identical to the parent. Colonies of bacteria sometimes caused mounded mineral accumulations called stromatolites to grow around them, but only rarely were the cells themselves preserved as fossils. Because of this lack of preserved cells, and also because rocks this old have almost always been recrystallized during later mountain-building episodes, very little is known about the first 4 billion years — 87 percent — of the Earth's history. All of this vast time span, from the creation of the entire Earth 4.7 billion years ago up to "only" 700 million years ago, is commonly lumped together as Precambrian Time.
Death Valley's Precambrian rocks are divided into three main sections. Oldest are high-grade metamorphic materials that make up much of the bedrock in Death Valley's mountain ranges. Little can be said about these rocks but, because of their original composition of sand and silt, we know they were deposited as sediment on a gentle floodplain about 1.8 billion years ago. Later they were severely metamorphosed during major mountain building. Those mountains were stripped away by erosion long before the end of the Precambrian. These rocks are exposed at the surface in relatively small areas. Two places where they can be easily seen are the cliffs above Badwater and along lower Wildrose Canyon below the campground.
Later, a series of sedimentary rocks known as the Pahrump Group was deposited. These formations — the Crystal Springs, Beck Spring, and Kingston Peak — were laid down mostly in a shallow marine environment. Later metamorphism affected them too, but it was less intense and the original sedimentary structures often remain visible. The most important aspect of these rocks is that sometime much later they were intruded by an igneous rock called diabase. Where it encountered the dolomite (calcium-magnesium carbonate) of the Crystal Springs Formation, large deposits of talc were formed.
Again, there was a hiatus before the deposition of sedimentary rocks resumed. These last Precambrian rocks are commonly assigned to the Vendian (or Ediacaran) Period, a time transitional to the Paleozoic Era. Trace fossils, such as burrows and feeding trails but not fossils of the animals that made them, are occasionally found in these rocks.
THE PALEOZOIC ERA
The abrupt appearance of complex multicellular life between about 700 million and 540 million years ago marks the end of the Precambrian and the start of the Paleozoic Era. In time, shallow ocean waters teemed with mollusks (clams and snails), echinoderms (starfish, urchins, and crinoids), arthropods (trilobites), brachiopods, and bryozoans. Many of the Paleozoic formations contain abundant fossils. Since the geologic time scale is based mostly on the fossil record, it is in the Paleozoic that time is first divided into spans shorter than eras. From oldest to youngest, these periods are called the Cambrian, Ordovician, Silurian, Devonian, Carboniferous-Mississippian, Carboniferous-Pennsylvanian, and Permian. Each period is represented within Death Valley National Park.
During the Paleozoic, the entire West Coast of North America was a quiet continental shelf. The setting was much like that along the East Coast of modern North America. There was dry land to the east, about where the Rocky Mountains are now, and gentle rivers flowed to the sea to deposit layers of sand, silt, and clay along the seashore. The water was clear and tropical most of the time, and extensive limestone platforms and reefs formed a short distance offshore. These layered rock formations make up most of the exposed rock in the Funeral, Grapevine, Panamint, Cottonwood, and Inyo mountains.
People often think of catastrophes when they consider geology, but the real stories of geology involve slow, uniform events. A total of more than 25,000 feet of sediment was deposited in this region during the Paleozoic Era. However, the era lasted 450 million years. Put together, this means that the sediment was deposited at a net average rate much less than one one-thousandth of an inch per year! Time was responsible for the vast accumulation of rock.
THE MESOZOIC ERA
Conditions abruptly changed at the end of the Paleozoic Era as the passive continental margin became part of an active igneous belt that was building a range of mountains. The unifying theory for geology is called plate tectonics. Masses of continental and oceanic rocks move as plates of crust on top of a deeper, semifluid material called the asthenosphere. It is a simple process. During those quiet Paleozoic years, North America was being carried eastward. At the end of the Paleozoic, it abruptly reversed its direction toward the west, causing a process called subduction.
Subduction occurs when a slab of oceanic crust is forced to slide beneath a plate of continental crust, such as North America. Some of the subducted plate melts, and magma rises up into the overriding material. During this particular mountain-building episode, called the Nevadan Orogeny (from oros, "mountain," and genes, "birth"), this region must have looked quite a lot like today's Cascade Range — rolling hills studded with volcanoes similar to Mt. St. Helens, Mt. Rainier, or Crater Lake's Mt. Mazama.
The start of the Nevadan Orogeny marks the beginning of the Mesozoic Era. Comprising the Triassic, Jurassic, and Cretaceous periods, it covers the geologic time span from about 250 million to 65 million years ago. The quiet sedimentary setting of earlier times was completely disrupted. (The only known Mesozoic sedimentary rock in the Death Valley region is the Butte Valley Formation, exposed in a limited part of the southern Panamint Mountains.) Intrusions of magma penetrated into the older rocks, cooling and solidifying as granite thousands of feet below the surface. The older sedimentary rocks were deformed and often recrystallized at high temperatures and pressures into a miscellany of metamorphic rocks, and solutions percolating through them created ore deposits of gold, lead-silver-zinc, and copper. Compression forced huge chunks of rocks to slide horizontally along thrust faults, superimposing the sequences of sedimentary formations on top of one another. At the surface, volcanoes erupted and laid down ash beds and lava flows.
It is only by chance that the Nevadan Orogeny occupied the entire Mesozoic Era. Elsewhere around the world this was the "Age of the Dinosaurs," but you will not find dinosaur remains in Death Valley. The environment was not suitable; there was very little dry land, and most of what did exist was on the slopes of the active volcanoes.
The volcanic rock eroded away long ago, since it was originally perched on top of everything else. Intrusive rocks can be found in many places, such as around the ghost town of Skidoo, on Hunter Mountain, in the Owlshead Mountains, and in other areas where high uplift and deep erosion have revealed what once were deep-seated materials.
THE CENOZOIC ERA
The Mesozoic Era and Nevadan Orogeny ended nearly simultaneously as time entered the Cenozoic Era. During this era the Basin and Range Province began to form, a process that started 65 million years ago and continues to this day. The Earth's crust was stretched by tension. Estimates are that the east-west distance across the entire Basin and Range Province has increased by at least 150 miles. To accommodate the stresses, the rocks fractured in a series of north-south faults along each of which the block of rock on one side moved up relative to the block on the other side. This kind of vertical movement produces what is called a normal dip-slip fault. The down-dropped valley blocks like Death, Panamint, and Saline valleys are grabens, whereas the intervening uplifted mountains such as the Panamint and Funeral Ranges are horsts. These alternating down-up-down-up fault blocks are the basins and ranges of the province. (In the Death Valley region each of the valleys has had much more fault activity along one side than the other, and the faults flatten into horizontal planes at depth. Technically, these modified normal faults are called listric faults, and the valleys are halfgrabens.)
As the valleys were pulled open, some of the rocks were twisted and bowed upward into broad curving forms. Where hard igneous and metamorphic rocks were overlain by softer sedimentary materials, the younger rocks literally slid off of the older. Pulled by gravity down into the valley via detachment faults, they quickly eroded away to expose curving turtleback surfaces of Precambrian basement rock. A series of turtlebacks is found in southeastern Death Valley, and the jumbled rocks of the Amargosa Chaos near Jubilee Pass show where another detachment fault began but did not complete the process.
As the mountains are thrown up relative to the valleys, erosion tries to strip them away. The debris is deposited as new sediment on the valley floors and hides much of the true geologic structure. The highest point in the Panamint Range at Telescope Peak reaches 11,049 feet above sea level. Directly below it, near Badwater, are the two lowest points in North America, both 282 feet below sea level, as measured by the U.S. Geological Survey. (Recent unofficial reports of an elevation of –289 are officially considered to be "misinformation.") That change of elevation is actually only about half the total relief. To reach the bedrock beneath Badwater, one would have to dig through nearly 9,000 feet of sand, gravel, and salt. The true amount of vertical fault offset has been more than 20,000 feet.
This basin and range faulting is only part of the structural story. The national park is also cut by strike-slip faults. On these most of the movement is horizontal. In effect, dip-slip faults create the mountain blocks, and strike-slip faults slide them past one another. The total offset along the Northern Death Valley Fault Zone through central Death Valley north toward Nevada may be as great as 50 miles. In a similar manner, the Southern Death Valley Fault Zone has generated as much as 20 miles of movement. Fully as important, probably, is the fault zone that links the Panamint Valley and Hunter Mountain faults into a single system perhaps 150 miles long.
These faults and uncountable others have slashed Death Valley's rocks into thousands of pieces. Each has been moved a bit differently than the others. Some are tilted on end, others severely folded, and a few are completely upside-down. The details are exceedingly complex, and geologists working with these exposures have recently reinterpreted many of their meanings. The complete story is far from being fully understood.
The geologic creation of Death Valley National Park is still underway. Every time a fault ruptures, the result is an earthquake. Reasonably fresh fault scarps formed by prehistoric shocks are visible along Badwater Road south of the Furnace Creek Inn, parallel to Scotty's Castle Road, and along the east side of Panamint Valley. Several earthquakes of significant size have occurred within the park area during the twentieth century. One on November 4, 1908, had a Richter magnitude of about 6.0 and was probably centered somewhere in the Panamint Mountains, possibly near Butte Valley. Another quake stuck south of, but near, Death Valley on November 15, 1916, with a magnitude of at least 6.1. And on May 17, 1993, a quake of magnitude 6.2 struck Eureka Valley. The largest earthquake to have actually occurred within the national park area in recorded time, this 1993 quake caused minor damage in Owens Valley but was not quite strong enough to form a new scarp. Finally, several small tremors were recorded at Harrisburg Flat in 1994, and there was a series of small (up to magnitude 4.4) quakes in the Slate Range near Trona in early December 2008. It is certain that more earthquakes, some of large scale, will take place in the future.
(Continues...)
Excerpted from The Explorer's Guide to Death Valley National Park by T. Scott Bryan, Betty Tucker-Bryan. Copyright © 2014 University Press of Colorado. Excerpted by permission of University Press of Colorado.
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