This 43-page report presents new data from the Willow Creek site that provides well-defined and narrow bounds on the times of the three youngest earthquakes on the southern strand of the Nephi segment, Wasatch Fault zone, and refines the time of the youngest earthquake to about 200 years ago. This is the youngest surface rupture on the entire Wasatch fault zone, which occurred about a century or less before European settles arrived in Utah. Two trenches at the Willow Creek site exposed three scarp-derived colluvial wedges that are evidence of three paleoearthquakes. OxCal modeling of ages from Willow Creek indicate that paleoearthquake WC1 occurred at 0.2 ± 0.1 ka, WC2 occurred at 1.2 ± 0.1 ka, and WC3 occurred at 1.9 ± 0.6 ka. Stratigraphic constraints on the time of paleoearthquake WC4 are extremely poor, so OxCal modeling only yields a broadly constrained age of 4.7 ± 1.8 ka. Results from the Willow Creek site significantly refine the times of late Holocene earthquakes on the Southern strand of the Nephi segment, and this result, when combined with a reanalysis of the stratigraphic and chronologic information from previous investigations at North Creek and Red Canyon, yield a stronger basis of correlating individual earthquakes between all three sites.
For most students, reading from a textbook provides only a framework of knowledge. The more comprehensive and perceptive grasp of a topic truly requires that one examines and answers thought-provoking questions and seeks solutions to meaningful problems. [The authors] goal in these studies is to provide such questions and pose such problems. [They] hope the exercises will help students understand how ancient conditions can be read from rocks and fossils, how geologic forces at the surface and within the planet can alter the environment and change world geography, and how events of the past can be placed within an integrated chronological sequence. The exercises are designed for students who may not intend to specialize in geology.-Pref.
Sculpted into graceful contours by countless centuries of wind and water, the Great Sand Dunes sprawl along the eastern fringes of the vast San Luis Valley of south-central Colorado. Covering an area of nearly thirty square miles, they are the tallest aeolian, or wind-produced, dunes in North America, towering 750 feet above the valley floor. With the addition of the enormous Baca Ranch and other adjacent lands, the dunes—originally designated as a National Monument in 1932—attained official National Park status in 2004. In Sea of Sand, Michael M. Geary guides readers on a historical journey through this unique ecosystem, which includes an array of natural and cultural wonders, from the main dunefield and verdant wetlands to the summits of the Sangre de Cristo Mountains. Described by explorer Zebulon Pike as “a sea in a storm” and by frontier photographer William Henry Jackson as “a curious and very singular phase of nature’s freak,” the Great Sand Dunes are a nexus of more than 10,000 years of human history, from Paleolithic big-game hunters to nomadic Native Americans, from Spanish conquistadores and transcontinental explorers to hard-rock miners and modern-day tourists in motor homes. Like these successive waves of visitors, Sea of Sand follows the water, analyzing its critical role in the settlement and development of the region. Geary also describes the profound impact that waves of human use and settlement have had on the land—which ultimately inspired the early grassroots efforts by San Luis Valley citizens to protect the dunes from further exploitation. He examines as well the more recent legislative effort led by an unprecedented coalition of local, state, and federal agencies and organizations, including The Nature Conservancy and the National Park Service, to secure the Great Sand Dunes’ national park designation. Amply illustrated, Sea of Sand is the definitive history of the natural, cultural, and political forces that helped shape this incomparable landscape.
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