Publications
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Geomorphic responses to dam removal in the United States – a two-decade perspective
Recent decades have seen a marked increase in the number of dams removed in the United States. Investigations following a number of removals are beginning to inform how, and how fast, rivers and their ecosystems respond to released sediment. Though only a few tens of studies detail physical responses to removals, common findings have begun to emerge. They include: (1) Rivers are resilient and resp
Authors
Jon J. Major, Amy E. East, Jim E. O'Connor, Gordon E. Grant, Andrew C. Wilcox, Christopher S. Magirl, Matthias J. Collins, Desiree D. Tullos
Abundant carbon in the mantle beneath Hawai`i
Estimates of carbon concentrations in Earth’s mantle vary over more than an order of magnitude, hindering our ability to understand mantle structure and mineralogy, partial melting, and the carbon cycle. CO2 concentrations in mantle-derived magmas supplying hotspot ocean island volcanoes yield our most direct constraints on mantle carbon, but are extensively modified by degassing during ascent. He
Authors
Kyle R. Anderson, Michael P. Poland
Evidence for degassing of fresh magma during the 2004-2008 eruption of Mount St. Helens: Subtle signals from the hydrothermal system
Results from chemical and isotopic analyses of water and gas collected between 2002 and 2016 from sites on and around Mount St. Helens are used to assess magmatic degassing related to the 2004-2008 eruption. During 2005 the chemistry of hot springs in The Breach of Mount St. Helens showed no obvious response to the eruption, and over the next few years, changes were subtle, giving only slight indi
Authors
Deborah Bergfeld, William C. Evans, Kurt R. Spicer, Andrew G. Hunt, Peter J. Kelly
Geologic field-trip guide to Mount Shasta Volcano, northern California
The southern part of the Cascades Arc formed in two distinct, extended periods of activity: “High Cascades” volcanoes erupted during about the past 6 million years and were built on a wider platform of Tertiary volcanoes and shallow plutons as old as about 30 Ma, generally called the “Western Cascades.” For the most part, the Shasta segment (for example, Hildreth, 2007; segment 4 of Guffanti and W
Authors
Robert L. Christiansen, Andrew T. Calvert, Timothy L. Grove
Geologic field-trip guide to the Lassen segment of the Cascades Arc, northern California
This field-trip guide provides an overview of Quaternary volcanism in and around Lassen Volcanic National Park, California, emphasizing the stratigraphy of the Lassen Volcanic Center. The guide is designed to be self-guided and to focus on geologic features and stratigraphy that can be seen easily from the road network.
Authors
Michael A. Clynne, L. J. Patrick Muffler
Geologic field-trip guide to Medicine Lake Volcano, northern California, including Lava Beds National Monument
Medicine Lake volcano is among the very best places in the United States to see and walk on a variety of well-exposed young lava flows that range in composition from basalt to rhyolite. This field-trip guide to the volcano and to Lava Beds National Monument, which occupies part of the north flank, directs visitors to a wide range of lava flow compositions and volcanic phenomena, many of them well
Authors
Julie M. Donnelly-Nolan, Timothy L. Grove
Overview for geologic field-trip guides to Mount Mazama, Crater Lake Caldera, and Newberry Volcano, Oregon
These field-trip guides were written for the occasion of the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) quadrennial scientific assembly in Portland, Oregon, in August 2017. The guide to Mount Mazama and Crater Lake caldera is an updated and expanded version of the guide (Bacon, 1989) for part of an earlier IAVCEI trip to the southern Cascade Range. The
Authors
Charles R. Bacon, Julie M. Donnelly-Nolan, Robert A. Jensen, Heather M. Wright
Field-trip guide to mafic volcanism of the Cascade Range in Central Oregon—A volcanic, tectonic, hydrologic, and geomorphic journey
The Cascade Range in central Oregon has been shaped by tectonics, volcanism, and hydrology, as well as geomorphic forces that include glaciations. As a result of the rich interplay between these forces, mafic volcanism here can have surprising manifestations, which include relatively large tephra footprints and extensive lava flows, as well as water shortages, transportation and agricultural disru
Authors
Natalia I. Deligne, Daniele Mckay, Richard M. Conrey, Gordon E. Grant, Emily R. Johnson, Jim O'Connor, Kristin Sweeney
Surface morphology of caldera-forming eruption deposits revealed by lidar mapping of Crater Lake National Park, Oregon- Implications for emplacement and surface modification
Large explosive eruptions of silicic magma can produce widespread pumice fall, extensive ignimbrite sheets, and collapse calderas. The surfaces of voluminous ignimbrites are rarely preserved or documented because most terrestrial examples are heavily vegetated, or severely modified by post-depositional processes. Much research addresses the internal sedimentary characteristics, flow processes, and
Authors
Joel E. Robinson, Charles R. Bacon, Jon J. Major, Heather M. Wright, James W. Vallance
Overview for geologic field-trip guides to volcanoes of the Cascades Arc in northern California
The California Cascades field trip is a loop beginning and ending in Portland, Oregon. The route of day 1 goes eastward across the Cascades just south of Mount Hood, travels south along the east side of the Cascades for an overview of the central Oregon volcanoes (including Three Sisters and Newberry Volcano), and ends at Klamath Falls, Oregon. Day 2 and much of day 3 focus on Medicine Lake Volcan
Authors
L. J. Patrick Muffler, Julie M. Donnelly-Nolan, Timothy L. Grove, Michael A. Clynne, Robert L. Christiansen, Andrew T. Calvert, Juliet Ryan-Davis
Dam removal: Listening in
Dam removal is widely used as an approach for river restoration in the United States. The increase in dam removals—particularly large dams—and associated dam-removal studies over the last few decades motivated a working group at the USGS John Wesley Powell Center for Analysis and Synthesis to review and synthesize available studies of dam removals and their findings. Based on dam removals thus far
Authors
Melissa M. Foley, James Bellmore, James E. O'Connor, Jeffrey J. Duda, Amy E. East, Gordon G. Grant, Chauncey W. Anderson, Jennifer A. Bountry, Mathias J. Collins, Patrick J. Connolly, Laura S. Craig, James E. Evans, Samantha Greene, Francis J. Magilligan, Christopher S. Magirl, Jon J. Major, George R. Pess, Timothy J. Randle, Patrick B. Shafroth, Christian E. Torgersen, Desiree D. Tullos, Andrew C. Wilcox
By
Ecosystems Mission Area, Natural Hazards Mission Area, Water Resources Mission Area, Volcano Hazards Program, Forest and Rangeland Ecosystem Science Center, John Wesley Powell Center for Analysis and Synthesis, Oregon Water Science Center, Pacific Coastal and Marine Science Center, Volcano Science Center, Western Fisheries Research Center, Columbia River Research Laboratory (CRRL)
Field-trip guide to the geologic highlights of Newberry Volcano, Oregon
Newberry Volcano and its surrounding lavas cover about 3,000 square kilometers (km2) in central Oregon. This massive, shield-shaped, composite volcano is located in the rear of the Cascades Volcanic Arc, ~60 km east of the Cascade Range crest. The volcano overlaps the northwestern corner of the Basin and Range tectonic province, known locally as the High Lava Plains, and is strongly influenced by
Authors
Robert A. Jensen, Julie M. Donnelly-Nolan