Geology Reports⌕ Search

Geology topics

C. Miller

Publications and source records attributed to C. Miller.

7 recordsLinked to original sources
USGS2016

Seismo-acoustic evidence for an avalanche driven phreatic eruption through a beheaded hydrothermal system: An example from the 2012 Tongariro eruption

The 6 August 2012 Te Maari eruption comprises a complex eruption sequence including multiple eruption pulses, a debris avalanche that propagated ~ 2 km from the vent, and the formation of a 500 m long, arcuate chasm, located ~ 300 m from the main eruption vent. The eruption included 6 distinct impulses that were coherent across a local infrasound network marking the eruption onset at 11:52:18 (all times UTC). An eruption energy release of ~ 3 × 1012 J was calculated using a body wave equation for radiated seismic energy. A similar calculation based on the infrasound record, shows that ~ 90% of the acoustic energy was released from three impulses at onset times 11:52:20 (~ 20% of total eruption energy), 11:52:27 (~ 50%), and 11:52:31 (~ 20%). These energy impulses may coincide with eyewitness accounts describing an initial eastward directed blast, followed by a westward directed blast, and a final vertical blast. Pre-eruption seismic activity includes numerous small unlocatable micro-earthquakes that began at 11:46:50. Two larger high frequency earthquakes were recorded at 11:49:06 and 11:49:21 followed directly by a third earthquake at 11:50:17. The first event was located within the scarp based on an arrival time location from good first P arrival times and probably represents the onset of the debris avalanche. The third event was a tornillo, characterised by a 0.8 Hz single frequency resonance, and has a resonator attenuation factor of Q ~ 40, consistent with a bubbly fluid filled resonator. This contrasts with a similar tornillo event occurring 2.5 weeks earlier having Q ~ 250–1000, consistent with a dusty gas charged resonator. We surmise from pre-eruption seismicity, and the observed attenuation change, that the debris avalanche resulted from the influx of fluids into the hydrothermal system, causing destabilisation and failure. The beheaded hydrothermal system may have then caused depressurisation frothing of the remaining gas charged system leading to the onset of explosive activity.

Journal of Volcanology and Geothermal Research↗
USGS2012

Ungulate management in national parks of the United States and Canada

Enabling legislation—that which gives appropriate officials the authority to implement or enforce the law—impacts management of ungulates in national parks of Canada and the United States (U.S.). The initial focus of such legislation in both countries centered on preserving natural and culturally significant areas for posterity. Although this objective remains primary, philosophies and practices have changed. A Canadian vision for ungulate management emerged during the latter half of the 20th century to protect and maintain or restore the ecological integrity of representative samples of the country’s 39 distinct landscapes, and to include provisions for traditional hunting and fishing practices representative of past cultural impacts on the environment. The current ungulate management approach in the U.S. relies on natural (ecological) processes, as long as normal conditions are promoted and there is no impairment of natural resources. Emphasizing natural processes as the basis has been a challenge because ecosystem dynamics are complex and management is multi-jurisdictional. Additionally, natural regulation typically will not prevent ungulates from reaching and sustaining densities that are incompatible with preservation or restoration of native flora and fauna, natural processes, or historical landscapes.

The Wildlife Society Technical Review↗
USGS2009

Wildland-urban interface maps vary with purpose and context

Maps of the wildland-urban interface (WUI) are both policy tools and powerful visual images. Although the growing number of WUI maps serve similar purposes, this article indicates that WUI maps derived from the same data sets can differ in important ways related to their original intended application. We discuss the use of ancillary data in modifying census data to improve WUI maps and offer a cautionary note about this practice. A comparison of two WUI mapping approaches suggests that no single map is "best" because users' needs vary. The analysts who create maps are responsible for ensuring that users understand their purpose, data, and methods; map users are responsible for paying attention to these features and using each map accordingly. These considerations should apply to any analysis but are especially important to analyses of the WUI on which policy decisions will be made.

Journal of Forestry↗
USGS2007

Hazards from hydrothermally sealed volcanic conduits

The 17 March 2006 eruption from Raoul Island (Kermadec arc, north of New Zealand) is interpreted as a magmatic‐hydrothermal event triggered by shaking associated with a swarm of local earthquakes. The eruption, which tragically claimed the life of New Zealand Department of Conservation Ranger Mark Kearney, occurred without significant volcanic seismicity or any of the precursory responses the volcanic hydrothermal system exhibited prior to a similarly sized eruption in 1964. Preliminary evidence suggests that the absence of precursory behavior is probably the consequence of hydrothermal sealing of the volcanic conduit since the 1964 eruption, and points to potential hazards associated with quiescent oceanic island volcanoes.

Eos, Transactions, American Geophysical Union↗
USGS2005

Suburban wildlife: Lessons, challenges, and opportunities

The United States, as well as most developed and many developing nations worldwide, is becoming increasingly urban and suburban.Although urban, suburban, and commercial development account for less than one percent to just over 20% of land use among states, 50-90% of the residents of those states can be classified as urban or suburban dwellers. The population of the U.S. as a whole has risen from being > 95% rural in the 1790s to about 80% urban-suburban today. With these changes in land use and demographic patterns come changes in values and attitudes; many urbanites and suburbanites view wildlife and nature differently than rural residents. These are among the challenges faced by wildlife biologists and natural resource managers in a rapidly urbanizing world. In 2003, we convened a symposium to discuss issues related to suburban wildlife. The papers presented in this special issue of Urban Ecosystems address the lessons learned from the early and recently rapidly expanding literature, the challenges we face today, and the opportunities that can help deal with what is one of the biggest challenges to conservation in a modernizing world. ?? 2005 Springer Science + Business Media, Inc.

Urban Ecosystems↗
USGS1981

Dark CO2-fixation and diurnal malic acid fluctuations in the submerged-aquatic Isoetes storkii

In the leaves (but not corms) of the submerged aquatic Isoetes storkii malic acid concentration fluctuated from 22 μeg g FW -1 in the evening to 171 μeg g FW -1 in the morning. Associated with this was a change in titratable acidity of 152 μeg g FW -1 between morning and evening. 14 C carbon was fixed in both the light and the dark, though the amount of carbon fixed in the light was more than that fixed in the dark. Autoradiographs show 88% of 14 CO 2 fixed in the dark is recovered after 1 h, in malic acid and the remainder in one other unidentified product, whereas these two products contain less than 15% of the 14 C fixed after 1 h exposure to 14 CO 2 in the light. It is suggested that CAM metabolism in this aquatic species may be related to the low availability of CO 2 for photosynthesis during the day in its aquatic environment and that this metabolic pathway may prove common in the genus Isoetes .

Oecologia↗