Stephen Blake

We aim here to improve the understanding of the relationship between emissivity of the lava and temperature by carrying out a multi-stage experiment for the 2017 Mt Etna (Italy) eruption. We combine laboratory, spaceborne, and numerical modelling data, to quantify the emissivity–temperature relationship. Our laboratory-based Fourier-transform infrared (FTIR) results indicate that emissivity and temperature are inversely correlated, which supports the argument that emissivity of molten material is significantly lower than that of the same material in its solid state. Our forward-modelling tests using MAGFLOW Cellular Automata suggest that a 35% emissivity variation (0.95 to 0.60) can produce up to 46% overestimation (for constant emissivity 0.60) in simulated/forecasted lava flow lengths (compared to actual observed). In comparison, our simulation using a ‘two-component’ emissivity approach (i.e., different emissivity values for melt and cooled lava) and constant emissivity 0.95 compares well (≤10% overestimation) with the actual 2017 lava flow lengths. We evaluated the influence of variable emissivity on lava surface temperatures using spaceborne data by performing several parametrically controlled assessments, using both constant (‘uniform’) and a ‘two-component’ emissivity approach. Computed total radiant fluxes, using the same spaceborne scene (Landsat 8 Operational Land Imager (OLI)), differ ≤15% depending on emissivity endmembers (i.e., 0.95 and 0.60). These results further suggest that computed radiant flux using high-spatial resolution data is bordering at lower boundary (range) values of the moderate-to-high temporal resolution spaceborne data (i.e., Moderate Resolution Imaging Spectroradiometer (MODIS) and Spinning Enhanced Visible and Infrared Imager (SEVIRI)), acquired for the same target area (and the same time interval). These findings may have considerable impact on civil protection decisions made during volcanic crisis involving lava flows as they approach protected or populated areas. Nonetheless, the laboratory work, reported here, should be extended to include higher volcanic eruptive temperatures (up to 1350 K).

Geophysical and geological observations collected in 2007-2012 shed light on the mechanisms controlling the style and location of eruptions within the Las Sierras-Masaya Caldera complex, Nicaragua. These results confirm a hypothesised ~3.5 km diameter structure with features compatible with the presence of a ring fracture (50-65°, with inward-dipping bounding walls). A central block is bound by this fracture and defines an incipient nested caldera related to the emptying of the magma chamber following the last Plinian eruption (1.8 ka). The prolongation of the Cofradías fault from the Managua graben represents the most significant structure on the floor of Masaya caldera. Current activity, including a convecting lava lake, largely depends on the interplay between the extensional stress regime associated with the Managua graben and deformation along the inner caldera bounding fault. This high spatial resolution survey uses a novel combination of geophysical methodologies to identify previously overlooked foci for future volcanic activity at Masaya.

The 1300 km3 tholeiitic lava flow field of the 14.98 Ma Roza Member of the Columbia River Basalt Province has the best-preserved vent system of any known continental flood basalt. Detailed geological mapping and logging of the exposed pyroclastic rocks along the >180-km-long vent system enable the reconstruction of pyroclastic edifices (partial cones) built around vents. The pyroclastic cones differ from those constructed during typical basaltic effusive eruptions and are characterized by low to moderate slope angles (1 km) fountains enhanced by fallout from the lower parts of convective plumes that rose above the fountains.\u

Variations to the global wetland CH₄ source strength in response to changes in orbital insolation patterns and atmospheric CO₂ concentration ([CO₂]_a) are hypothesized to play an important role in determining glacial‐interglacial variations in atmospheric CH₄ concentration ([CH₄]_a). Here the interactive effects of temperature, a major controlling variable determining wetland CH₄ flux, and the low [CO₂]_a of glacial intervals are investigated for the first time. We measured the temperature dependence of CH₄ emissions from replicated mesocosms (n = 8 per CO₂ treatment) collected from a minerotrophic fen and an ombrotrophic bog incubated in either ambient (c. 400 ppm) or glacial (c. 200 ppm) [CO₂]_a located in the United Kingdom. CH₄ fluxes were measured at 5°C, 10°C, 15°C, 20°C, and 25°C and then in reverse order over a 20 day period under each [CO₂]_a treatment. Results showed that the Q₁₀ temperature response of CH₄ emissions from the Carex/Juncus‐dominated fen declined significantly by approximately 39% under glacial [CO₂]_a (ambient [CO₂]_a = 2.60, glacial [CO₂]_a = 1.60; P < 0.01). By contrast, the response of CH₄ emissions from the Sphagnum‐dominated bog remained unaltered (ambient [CO₂]_a = 3.67, glacial [CO₂]_a = 3.67; P > 0.05). This contrasting response may be linked to differences in plant species assemblage and the varying impact of CO₂ starvation on plant productivity and carbon availability in the rhizosphere. Furthermore, our results provide empirical evidence to support recent model‐based indications that glacial‐interglacial variations in [CH₄]_a may be explained by changes in wetland CH₄ source strength in response to orbitally forced changes in climate and [CO₂]_a.