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Alluvial fans are ubiquitous geomorphological features that occur throughout the world, regardless of climate, at the front of mountains as the result of erosion and deposition. They are more prominent in semi- and arid climates simply because of the lack of vegetative cover that masks their fan shapes in more humid areas. From both engineering and geological viewpoints, alluvial fans present particular fluvial and sedimentation hazards in semi- and arid regions because episodic rainfall-runoff events can result in debris, mud, and fluvial flows through complex and, in some cases, migratory channel systems. Further, in semi- and arid climates alluvial fans often end in terminal or playa lakes. Given the uniform topography of playa lakes, these features often present ideal locations for facilities such as airports; however, regardless of the engineering advantages of the topography, the episodic and often long-term flooding of these lakes attracts migratory birds. The purpose of this volume is to summarize the current state-of-the-art, from the viewpoint of engineering, in the identification and mitigation of flood hazard on alluvial fans; and to accomplish this a fundamental understanding of geology is required.
Part natural history, part call to conservation, and part love song, this evocative and informative excursion into the Sonoran Desert along the U.S.-Mexico border brings to life the beauty of a sparse and seductive terrain.
This 116-page report presents the results of an investigation by the Utah Geological Survey of land subsidence and earth fissures in Cedar Valley, Iron County, Utah. Basin-fill sediments of the Cedar Valley Aquifer contain a high percentage of fine-grained material susceptible to compaction upon dewatering. Groundwater discharge in excess of recharge (groundwater mining) has lowered the potentiometric surface in Cedar Valley as much as 114 feet since 1939. Groundwater mining has caused permanent compaction of fine-grained sediments of the Cedar Valley aquifer, which has caused the land surface to subside, and a minimum of 8.3 miles of earth fissures to form. Recently acquired interferometric synthetic aperture radar imagery shows that land subsidence has affected approximately 100 mi² in Cedar Valley, but a lack of accurate historical benchmark elevation data over much of the valley prevents its detailed quantification. Continued groundwater mining and resultant subsidence will likely cause existing fissures to lengthen and new fissures to form which may eventually impact developed areas in Cedar Valley. This report also includes possible aquifer management options to help mitigate subsidence and fissure formation, and recommended guidelines for conducting subsidence-related hazard investigations prior to development.
Excerpt from Placer Gold Deposits of Nevada Following the discovery of placers at Gold Canyon, placer discoveries in Nevada were broadly in three periods: the 1860's to 1880's, when many small deposits throughout the State were discovered and sporadically worked and several large placers were discovered and extensively worked; the short period between 1906 and 1910, when very rich placers were dis covered at Lynn, Battle Mountain, Manhattan, and Round Mountain; the early 1930's, when economic conditions created by the depression caused a renewed interest in placer mining, and many individuals sought, and a few discovered, new placer areas throughout the State. The location of the placers described in this report is shown on plate 1. Very little factual information can be found about the early periods of placer mining in Nevada. For many placers, the only reports available are hearsay estimates of production and speculations about the extent of the placer ground based on remnants of placer pits, shafts, and other workings. Many of the placers said to have had a high production between 1860 and 1890 were worked by Chinese miners who came to Nevada dur ing the building of the railroads and stayed on to work at mining and other activities. The Chinese were reputed to be secretive with their earnings from the placers and did not ship the gold to the mint by Wells Fargo or other shippers. They worked the gravels very thoroughly in areas where American miners did not wish to expend great labor to win the gold. The placers in the Sierra and Spring Valley districts, Pershing County, were worked by Chinese miners; they have a very high estimated production before 1900 and a comparatively low known production since that time. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.
Some of the most striking and beautiful of all landscapes that can be formed by natural geological and climatic processes can be found in Arizona. This volume is designed to present the reader with visual images of many of the spectacular landscapes of Arizona, their relationship to each other, and explanations of the dynamic aspects of their development over millions of years. Replete with photographs, this valuable reference work will be useful to all students of geology, particularly that of Arizona.
The 52 papers in this vary in content from summaries or state-of-knowledge treatments, to detailed contributions that describe new species. Although the distinction is subtle, the title (Vertebrate Paleontology in Utah) indicates the science of paleontology in the state of Utah, rather than the even more ambitious intent if it were given the title “Vertebrate Paleontology of Utah” which would promise an encyclopedic treatment of the subject. The science of vertebrate paleontology in Utah is robust and intense. It has grown prodigiously in the past decade, and promises to continue to grow indefinitely. This research benefits everyone in the state, through Utah’s muse ums and educational institutions, which are the direct beneficiaries.