Filtering by
- All Subjects: Petrology
- Creators: School of Earth and Space Exploration
- Creators: Roggensack, Kurt
The Star Planet Activity Research CubeSat (SPARCS) will be a 6U CubeSat devoted to photometric monitoring of M dwarfs in the far-ultraviolet (FUV) and near-ultraviolet (NUV) (160 and 280 nm respectively), measuring the time-dependent spectral slope, intensity and evolution of M dwarf stellar UV radiation. The delta-doped detectors baselined for SPARCS have demonstrated more than five times the in-band quantum efficiency of the detectors of GALEX. Given that red:UV photon emission from cool, low-mass stars can be million:one, UV observation of thes stars are susceptible to red light contamination. In addition to the high efficiency delta-doped detectors, SPARCS will include red-rejection filters to help minimize red leak. Even so, careful red-rejection and photometric calibration is needed. As was done for GALEX, white dwarfs are used for photometric calibration in the UV. We find that the use of white dwarfs to calibrate the observations of red stars leads to significant errors in the reported flux, due to the differences in white dwarf and red dwarf spectra. Here we discuss the planned SPARCS calibration model and the color correction, and demonstrate the importance of this correction when recording UV measurements of M stars taken by SPARCS.
Multiple eruption styles can be observed in a single eruptive sequence. In recent decades, transitions in eruption style during well-documented eruptions have been described in detail, with some workers proposing explanatory mechanisms for the transitions. These proposed mechanisms may be broadly classified into processes at depth, processes in the conduit, or some combination of both.
The present study is focused on the Pietre Cotte sequence because it may have encompassed up to three different eruptive cycles, each representing different degrees of explosivity. The first deposits are composed of repeated layers of fine ash and lapilli composed of latite and rhyolite endmembers, efficiently mixed at sub-cm scales. The thin layers and bubble/crystal textures indicate that the magma underwent numerous decompressions and open-system degassing, and that the eruptions waned with time. The second phase of the sequence appears to have been initiated by cm-scale mixing between a volatile-rich, mafic magma from deeper in the system and a shallow silicic body. Textures indicate that the magma ascended rapidly and experienced little to no open-system degassing. The final phase of the sequence again produced repeated layers of fine ash and lapilli, of uniform trachyte composition, and waned with time. The first and last phases were likely produced in Vulcanian eruptions, while the pumice-rich layers were likely produced in Vulcanian to sub-Plinian eruptions.
In summary, the Pietre Cotte sequence is characterized by up to three magma recharge events in ~200 years. The differences in eruptive style appear to have been controlled by variations in the volatile content of the recharge magma, as well as the efficiency and scale of magma mixing and resulting overpressures.
Tecolote Volcano in the Pinacate Volcanic Field in Mexico contains multiple vents within a horseshoe-shaped crater that have all produced various ejecta (Zawacki et al. 2019). The objectives of this research are to map ballistic distribution to understand the relationship between the source vent or vents and the bombs and ballistics that litter the region around Tecolote, and interpret the eruption conditions that ejected those bombs by using their distributions, morphologies, and fine-scale textures.
The findings of this work are that these bombs are apparently from the last stages of the eruption, succeeding the final lava flows. The interiors and exteriors of the bombs display different cooling rates which can are indicated by the fabric found within. Using this, certain characteristics of the bombs during eruption were extrapolated. The ‘cow pie’ bombs were determined to be the least viscous or contained a higher gas content at the time of eruption. Whereas the ribbon/rope bombs were determined to be the most viscous or contained a lesser gas content. Looking at the Southern Bomb Field site, it is dominated by large bombs that were during flight were molded into aerodynamic shapes. The Eastern Rim site is dominated by smaller bombs that appeared to be more liquid during the eruption. This difference in the two sites is a probable indication of at least two different eruptive events of different degrees of explosivity. Overall, aerodynamic bombs are more common and extend to greater distances from the presumed vent (up to 800 m), while very fluidal bombs are uncommon beyond 500 meters. Fluidal bombs (‘cow pie’, ‘ribbon’, ‘rope/spindle’) show a clear trend in decreasing size with distance from vent, whereas the size-distance trend is less dramatic for the aerodynamic bombs.