We have obtained two results since leaving Chapter 3 which make this return to βℕ possible. The first of these was Corollary 4.30 in which we found, under the assumption of the Continuum Hypothesis, that ℕ* contains a dense subset of 2C P-points. The second was Corollary 6.30 in which we saw that no point of ℕ* has its own type as a relative type with respect to any copy of ℕ contained in ℕ*. Here we will make use of these two properties of ℕ* to continue the investigation of βℕ and especially of ℕ*.

β ℕ Revisited

Himalayan glacier tongues are commonly debris covered and they are an important source of melt water. However, they remain relatively unstudied because of the inaccessibility of the terrain and the difficulties in field work caused by the thick debris mantles. Observations of debris-covered glaciers are therefore scarce and airborne remote sensing may bridge the gap between scarce field observations and coarse resolution space-borne remote sensing. In this study we deploy an Unmanned Aerial Vehicle (UAV) before and after the melt and monsoon season (May and October 2013) over the debris-covered tongue of the Lirung Glacier in Nepal. Based on stereo-imaging and the structure for motion algorithm we derive highly detailed ortho-mosaics and digital elevation models (DEMs), which we geometrically correct using differential GPS observations collected in the field. Based on DEM differencing and manual feature tracking we derive the mass loss and the surface velocity of the glacier at a high spatial accuracy. On average, mass loss is limited and the surface velocity is very small. However, the spatial variability of melt rates is very high, and ice cliffs and supra-glacial ponds show mass losses that can be an order of magnitude higher than the average. We suggest that future research should focus on the interaction between supra-glacial ponds, ice cliffs and englacial hydrology to further understand the dynamics of debris-covered glaciers. Finally, we conclude that UAV deployment has large potential in glaciology and it may revolutionize methods currently applied in studying glacier surface features.

High-Resolution Monitoring of Himalayan Glacier Dynamics Using Unmanned Aerial Vehicles

Natural dust is often associated with hot, subtropical deserts, but significant dust events have been reported from cold, high latitudes. This review synthesizes current understanding of high-latitude (> or = 50degN and > or = 40degS) dust source geography and dynamics and provides a prospectus for future research on the topic. Although the fundamental processes controlling aeolian dust emissions in high latitudes are essentially the same as in temperate regions, there are additional processes specific to or enhanced in cold regions. These include low temperatures, humidity, strong winds, permafrost and niveo-aeolian processes all of which can affect the efficiency of dust emission and distribution of sediments. Dust deposition at high latitudes can provide nutrients to the marine system, specifically by contributing iron to high-nutrient, low-chlorophyll oceans; it also affects ice albedo and melt rates. There have been no attempts to quantify systematically the expanse, characteristics, or dynamics of high-latitude dust sources. To address this, we identify and compare the main sources and drivers of dust emissions in the Northern (Alaska, Canada, Greenland, and Iceland) and Southern (Antarctica, New Zealand, and Patagonia) Hemispheres. The scarcity of year-round observations and limitations of satellite remote sensing data at high latitudes are discussed. It is estimated that under contemporary conditions high-latitude sources cover >500,000 sq km and contribute at least 80-100 Tg/yr1 of dust to the Earth system (approx. 5% of the global dust budget); both are projected to increase under future climate change scenarios.

/pdf/high-latitude-dust-in-the-earth-system-1x54k3smcp.pdf

High Latitude Dust in the Earth System

Introduction To Modern Photogrammetry

How to make porphyry copper deposits

https://research-information.bris.ac.uk/files/76554515/1_s2.0_S221424281500039X_main.pdf

Optimising shape analysis to quantify volcanic ash morphology

Unoccupied aircraft systems (UAS) are developing into fundamental tools for tackling the grand challenges in volcanology; here, we review the systems used and their diverse applications. UAS can typically provide image and topographic data at two orders of magnitude better spatial resolution than space-based remote sensing, and close-range observations at temporal resolutions down to those of video frame rates. Responsive deployments facilitate dense time-series measurements, unique opportunities for geophysical surveys, sample collection from hostile environments such as volcanic plumes and crater lakes, and emergency deployment of ground-based sensors (and robots) into hazardous regions. UAS have already been used to support hazard management and decision-makers during eruptive crises. As technologies advance, increasing system capabilities, autonomy and availability, supported by more diverse and lighter-weight sensors, will offer unparalleled potential for hazard monitoring. UAS will provide opportunities for pivotal advances in our understanding of complex physical and chemical volcanic processes.

https://www.jvolcanica.org/ojs/index.php/volcanica/article/download/48/69

Volcanological applications of unoccupied aircraft systems (UAS): Developments, strategies, and future challenges

The abundant fine ash produced in the 2011 subglacial eruption of Grimsvotn, Iceland, highlights the fragmentation efficiency of mafic hydromagmatic eruptions, which is considerably higher than for comparable “dry” eruptions. Ash from the 2011 eruption can be divided into three morphological components—vesicular particles, shards, and dense fragments—distinguished by the size and abundance of constituent vesicles. We use the vesicle characteristics to define a new shape factor, the concavity index, which provides an unbiased way to classify individual ash particles as either bubbly (vesicular particles and shards) or dense. The relative proportion of bubbly and dense particles varies systematically with grain size, with the proportion of bubbly grains decreasing as the particle size approaches the modal bubble diameter. Measured bubble volume distributions are similar to those of rapidly quenched pyroclasts from Hawaiian fountains and suggest a comparable degassing history during magma ascent. Yet concordance between the size distributions of ash and of bubbles in the Grimsvotn samples stands in contrast to the size distributions in Hawaiian fountains, where pyroclasts are orders of magnitude larger than individual bubbles. We propose that the Grimsvotn ash formed by brittle disintegration of vesicular pyroclasts and that fragmentation efficiency was amplified by residual thermal stresses in glass quenched by glacial water. The strong control of resulting particle sizes and morphologies by the size and spatial distribution of bubbles demonstrates that the bubble population cannot be ignored when modeling hydromagmatic fragmentation.

The role of bubbles in generating fine ash during hydromagmatic eruptions

Recent eruptions in Iceland and Chile have demonstrated that volcanic ash problems persist long after an eruption For this reason, ash dispersion models are being extended to include ash remobilization Critical to these models is knowledge of the ash source and the particle sizes that can be mobilized under different wind and moisture conditions Here we characterize the physical and chemical characteristics of ash deposited on new snow in Reykjavik, Iceland, following a blizzard on 6 March 2013 Morphological, textural, and compositional analyses indicate resuspension from multiple eruptive deposits, including both Grimsvotn (2011) and Eyjafjallajokull (2010) eruptions Grain size measurements show a mode of 32–63 µm, with particles as large as 177 µm; there is little mass in the very fine fraction, ≤10 µm (PM10) We compare our observations to predictions using the Lagrangian particle dispersion model, NAME (UK Met Office) The model output is consistent with observations in that it forecasts resuspension from both Eyjafjallajokull and Grimsvotn source regions, and shows ash deposition coincident with the timing of observed deposition in Reykjavik The modeled deposit in Reykjavik predicts, however, a substantially lower proportion of Grimsvotn ash than observed This discrepancy has highlighted the need to reassess the assumptions used in the simulations, particularly regarding the source area and precipitation thresholds Furthermore, we suggest that modification of ash deposits in the form of erosion, redeposition, compaction, or cementation may influence the dynamics of resuspension over time, thus influencing the ability of model simulations to accurately forecast remobilization events

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2014JD021598

Ash mists and brown snow: Remobilization of volcanic ash from recent Icelandic eruptions

As well as gases that regulate climate over geological time, volcanoes emit prodigious quantities of metals into the atmosphere, where they have key roles as catalysts, pollutants and nutrients. Here we compare measurements of arc basaltic volcano metal emissions with those from hotspot settings. As well as emitting higher fluxes of metals (similar to those building ore deposits), these arc emissions possess a distinct compositional fingerprint, particularly rich in tungsten, arsenic, thallium, antimony and lead when compared with those from hotspots. We propose that volcanic metal emissions are controlled by magmatic water content and redox: hydrous arc magmas that do not undergo sulfide saturation yield metal-rich, saline aqueous fluid; shallow degassing and resorption of late-stage sulfides feeds volcanic gases in Hawai’i and Iceland. Although global arc magma chemistries vary considerably, our findings suggest that volcanic emissions in arcs have a distinct fingerprint when compared with other settings. A shift in global volcanic metal emissions may have occurred in Earth’s past as more oxidized, water-rich magmas became prevalent, influencing the surface environment. Arc volcanism emits higher metal fluxes to Earth’s atmosphere than hotspot volcanism. The systems’ unique gas compositions are controlled by magmatic water content and redox state, as shown by a compilation of volcanic gas and aerosol metal data.

/pdf/a-distinct-metal-fingerprint-in-arc-volcanic-emissions-3lxtbguyg5.pdf

Emma J. Liu

Papers

Optimising shape analysis to quantify volcanic ash morphology

Volcanological applications of unoccupied aircraft systems (UAS): Developments, strategies, and future challenges

The role of bubbles in generating fine ash during hydromagmatic eruptions

Ash mists and brown snow: Remobilization of volcanic ash from recent Icelandic eruptions

A distinct metal fingerprint in arc volcanic emissions