Recent schematic diagrams for the three big active caldera systems in the Western U.S.A. There are many other caldera systems around the world (e.g., Hughes and Mahood 2008), and the focus on examples from the U.S.A. here is solely due to personal acquaintance. (a) Valles caldera (Wilcock et al. 2010), (b) Long Valley caldera (Hildreth 2004), (c) Yellowstone, Official web site and Lowenstern and Hurvitz (2008).
Examples of diffusional profiles in quartz crystals from Taupo, New Zealand (Matthews et al. 2012), in pyroxene crystals from the Bishop Tuff, California, U.S.A. (Chamberlain et al. 2014a), and plagioclase crystals from Cosigüina, Nicaragua (Longpré et al. 2014).
Injection of negatively buoyant droplets of (low-viscosity) water dyed in green into a tank filled with (more viscous) silicon oil (from Faroughi and Huber 2015). Droplet interactions, even in the presence of droplet trains, can significantly reduce the settling velocity and decrease the rate of phase separation.
Example of granular scale calculation for multiphase magma chamber dynamics. (a–c) modified from from Furuichi and Nishiara (2014) for crystal settling from a stratified chamber with a crystal-free region at the bottom and a denser, crystal-rich horizon, at the top, and (d) Parmigiani et al. 2011 for the migration of a buoyant volatile phase in a crystal-rich rigid magma.
Crystallinity variations in magmas, from solidus to liquidus, which can span up to 250 °C (modified from Marsh 1996). The typical amount of heat liberated by 1 kg of magma from liquidus to solidus is ~600 000 J, of which ~½ is from latent heat.
Schematic temperature-time diagram for a part of mature magma reservoirs situated in the hottest, core zone. Note the slower cooling rates as the crystal content increases (magma approaching their solidus).
Comparison between the SRMVF batholith model (Lipman and Bachmann 2015). (a and b) Schematized cross sections based on erupted products and gravity data and a joint ambient noise-receiver function inversion S-velocity model for the Altiplano region of the Andes (c) Ward et al. (2014).
(a) Variations in SiO2 and crystal contents for ignimbrites in western United States (LC = Lava Creek Tuff; T = Tshigere Member of Bandelier Tuff; BT = Bishop Tuff; WP = Wason Park Tuff; CR = Carpenter Ridge Tuff; RC = Rat Creek Tuff; NM = Nelson Mountain Tuff; AT = Ammonia Tanks Tuff; FC = Fish Canyon Tuff; BC = Blue Creek Tuff; SM = Snowshoe Mountain Tuf; MP = Masonic Park Tuff). Modified from Hildreth (1981) and Huber et al. (2012a); data from Hildreth (1981) and Lipman (2000, 2006). (b) REE patterns from crystal-poor pumices and crystal-rich clasts from the Carpenter Ridge Tuff, with, for reference, patterns for lamproïtic magmas, indicating that mixing with such high-K, incompatible-element-enriched liquids is not an option to generate the high-Ba-Zr composition of the late-erupted crystal-rich clasts (modified from Bachmann et al. 2014).
Schematic diagram of the polybaric mush model [modified from Lipman (1984), Hildreth (2004), and Bachmann and Bergantz (2008c). (1) Pre-existing crust, (2) upper mantle, (3) feeding zone of primitive magmas from the mantle (“basalt s.l.”), (4) lower crustal mush zone, with internal variability in melt content, (5) upper crustal mush zone, (6) melt-rich pockets in upper crust, (7) melt-rich pockets in the lower crust, (8) caldera structure, (9), stratovolcano (e.g., Mount St. Helens, Washington, U.S.A.).
Phase maps of crystal-rich ignimbrites, both remobilized crystal mushes at different stages of rejuvenation; the Masonic Park Tuff no longer has any sanidine and shows only tiny quartz microcrysts, whereas the Fish Canyon Tuff still shows large, albeit highly resorbed quartz and sanidine phenocrysts (Bachmann et al. 2002). In both cases, plagioclase and mafic crystals (hornblende in the FCT, and pyroxene in the MPT) show reverse zoning (Lipman et al. 1996; Bachmann and Dungan 2002).
(a) Compositional groups observed in the Kos-Nisyros volcanic center (Eastern Aegean; see Pe-Piper and Moulton 2008 and Francalanci et al. 1995). (b) Tri-modality in compositions of volcanic rocks from Tenerife (modified from Sliwinski et al. 2015).
Example of a cross section through a well-exposed pluton (Searchlight pluton, Nevada), showing areas rich in crystallized melts and areas with cumulate characteristics, but still containing trapped melt (modified from Bachl et al. 2001; Gelman et al. 2014).
Examples of volcanic eruptions (both explosive and effusive, from arc and non-arc systems) with and without excess sulfur (modified from Shinohara 2008). Excess S is based on the mismatch between the SO2 flux measured during volcanic eruptions (y-axis; typically done by spectroscopic methods or ice core data) and petrological estimates based on the difference in S content between melt inclusions and interstitial glass, estimating the amount of S released by the eruptive decompression process (x-axis). Calculated second boiling effect (gray inclined bar) is from a bubble growth model tracking the evolution of S partitioning between melt, crystals, and an exsolved gas phase in a cooling and crystallizing magma reservoir (from 5 to 50 vol% crystals; from Su et al. 2016).
A caldera cycle recorded by changes in temperature, oxygen fugacity, bulk-rock composition, and mineralogy in the Kos-Nisyros volcanic system, eastern Aegean. Pre-caldera units (Kefalos domes and pyroclastic units) show highly evolved magma compositions (high-SiO2 rhyolites), low temperature, oxidized, and water-rich conditions, similar to the caldera-forming event (Kos Plateau Tuff, KPT). Following the KPT, Nisyros volcano built up, generating more typically less evolved magmas, including two large rhyodacitic units (Lower Pumice and Upper Pumice), with drier, more reduced compositions, and hotter magma temperatures. Similar cycles have been suggested for the Taupo Volcanic Zone, in New Zealand (modified from Bachmann et al. 2012).