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Radon in Groundwater of the Long Valley Caldera, California
Published in Barbara Graves, Radon, Radium, and Other Radioactivity in Ground Water, 2020
Steve Flexser, Harold A. Wollenberg, Alan R. Smith
The Long Valley caldera is an area of active volcanism and ongoing seismic activity. Because of the potential seismic and volcanic hazards, as well as the intrinsic geological importance of the area, various geophysical and geochemical parameters have been and continue to be monitored at sites within and adjacent to the caldera. Among these prameters are hydrogen, helium, and radon in soil gas, and chemical constituents of groundwaters. Long Valley is therefore an excellent site for close comparison between variations in groundwater radon and other geochemical and geophysical variations.
Hydrogen Economy, Geothermal and Ocean Power, and Climate Change
Published in Roy L. Nersesian, Energy Economics, 2016
Three types of geothermal power plants generate electricity. First is a dry steam geothermal reservoir in which emitted steam directly spins a turbine. These are relatively rare and were the first dedicated to generating electricity. One in Tuscany has been in operation since 1904, and The Geysers, 90 miles north of San Francisco, has been in operation since 1960. The Geysers represents the largest single source of tapped geothermal energy in the world and generates enough electricity to supply a city the size of San Francisco. A falloff in steam pressure in the 1990s was successfully countered by water injection to replenish the geothermal reservoir. Injected water was waste treatment water from neighboring communities, an innovative and environmentally safe method of disposal. Some thought has been given to tapping the world’s largest source of geothermal energy, Yellowstone, the caldera of a supervolcano that last erupted 600,000 years ago. (Another eruption of that magnitude would wipe out half of the US and emit an ash cloud large enough to send the planet into a “volcanic” winter.) But Yellowstone, as a national park, cannot be commercially developed.
Volcanic activity
Published in F.G. Bell, Geological Hazards, 1999
Most calderas measure several kilometres across and are thought to be formed by collapse of the superstructure of a volcano into the magma chamber below (Figure 2.3), since this accounts for the small proportion of pyroclastic deposits that surround the crater. If they had been formed as a result of tremendous explosions, then fragmentary material would be commonplace.
Cenozoic volcanism, tectonics and mineralisation of Woodlark Island (Muyuw), eastern Papua
Published in Australian Journal of Earth Sciences, 2021
Uvarakoi Caldera is centred on the Busai–Bomagai area (Figure 3). It is a felsic volcanic system and appears to have erupted synchronously with the Watou Mountain Eruptive Centre. The caldera was formed during a series of violent explosive eruptions by rapid removal of magma from the underlying chamber, followed by collapse (Lindley, 2016). The intracaldera sequence includes the Busai Hill Ignimbrite, and the size of the collapsed caldera is indicated by the 7 km2 areal extent of this ponded unit (Lindley, 2016). The widely dispersed and highly fragmented tuff deposits of the Monasiy Tuff have been mapped up to 15 km from the caldera on the Suloga Peninsula. These outflow facies tuffs were the result of magma–water mixing in the surface environment. The Uvarakoi Caldera appears to have been small compared with average dimensions of felsic systems. The caldera probably had a lifespan in the order of 105–106 years (Lindley, 2016).
A two million-year history of rifting and caldera volcanism imprinted in new gravity anomaly compilation of the Taupō Volcanic Zone, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2021
Vaughan Stagpoole, Craig Miller, Fabio Caratori Tontini, Thomas Brakenrig, Nick Macdonald
Active, caldera-forming, silicic magma systems represent one of most hazardous forms of volcanism on Earth and can occur in a variety of tectonic settings. Knowledge of the size, location and structural setting of caldera volcanoes is therefore important for accurately interpreting monitoring data and informing hazard assessments. Internationally, gravity data has been used to investigate volcanic regions and is often modelled in conjunction with other data to determine crustal structure (e.g. DeNosaquoa et al. 2009; Hasegawa et al. 2009; Hautmann et al. 2013), interpret magma reservoirs (e.g. del Potro et al. 2013; Miller et al. 2017; Paulatto et al. 2019) and study the interactions between caldera-forming magmatism and tectonism (e.g. Saxby et al. 2016; Jorgensen and Zhdanov 2019). In New Zealand, the Taupō Volcanic Zone (TVZ) forms the southernmost part of a c. 2800-km-long Tonga-Kermadec back-arc system (Figure 1). It is a region of continental rifting (Stern 1985; Rowland and Sibson 2001; Rowland et al. 2010; Villamor et al. 2017) and has been the centre of frequent and very productive silicic volcanism and geothermal activity (Houghton et al. 1995; Wilson et al. 1995, 2009; Barker et al. 2020). Mesozoic metasedimentary basement rocks fringe and underlie the TVZ (Mortimer 2004; Leonard et al. 2010; Milicich et al. 2020). Since rifting and volcanism began the basement has subsided or been replaced by plutonic rocks with the resulting depression filled with a large thickness of low-density pyroclastic rocks (mainly ignimbrite) and unconsolidated volcanogenic material (Villamor and Berryman 2006; Leonard et al. 2010).
Taupō: an overview of New Zealand's youngest supervolcano
Published in New Zealand Journal of Geology and Geophysics, 2021
Simon J. Barker, Colin J.N. Wilson, Finnigan Illsley-Kemp, Graham S. Leonard, Eleanor R.H. Mestel, Kate Mauriohooho, Bruce L.A. Charlier
In the case of composite cone volcanoes, the physical entity of the cone (e.g. Ruapehu, Taranaki) or cones (e.g. Tongariro) provides a focal point for definitions of the volcano, whether in a scientific sense or through cultural tradition. Reference made to the main vent or additional features such as satellite vents (e.g. Pukeonake, Ohakune) makes it apparent that there is a central focus to be referred to as a volcano, reflecting a long-lived, multiple use conduit system. In contrast, volcanoes that produce high-silica eruption products (i,e., rhyolite) have complex morphologies (e.g. Taupō, Okataina), resulting from a wide range of eruptive styles and sizes, and a lack of a single central focus for vents. Rather than forming a conical peak, rhyolitic volcanoes often comprise either an irregular heap of effusive lava domes (e.g. Maroa, Okataina), and/or a caldera structure that forms during large explosive eruptions (e.g. Rotorua, Taupō). Caldera collapse results in a negative topographic feature, termed (in the Taupō context) an ‘inverse volcano’ type by Walker (1981a). Collapse is caused by the sheer volume of magma that is evacuated from the crust (Lipman 1997; Cole et al. 2005), highlighting the huge size of the underlying silicic magmatic system (Hildreth 1981; Bachmann and Huber 2016). As such, caldera volcanoes generate the most explosive and voluminous volcanic eruptions, associated with widespread hazards (e.g. ashfall, pyroclastic flows) that represent a source of major volcanic risk (Self 2006; Acocella et al. 2015). In addition, however, they are associated with significant mineral and geothermal resources (e.g. John 2008; Chambefort and Bignall 2016; Christie et al. 2019) and landscapes of great cultural significance and beauty (Stokes 2000).