GeoResJ最新文献

Recent datasets on heterogeneous deposition mode ice nucleation have revealed a strong dependence of the contact parameter m on temperature, ranging from linear to exponential, depending on the experiments. We analyze recent datasets using a Monte Carlo Markov Chain method with the full classical nucleation theory including spherical and planar geometry. The method we use allows us to test models of the temperature dependence of the contact parameter and evaluate their performance. We estimate the applicability of different forms of contact parameter temperature dependence, including a new well-behaved suggestion. Such a function has a more physical behavior at high and low temperatures and might thus be more easily applicable in atmospheric modeling. However, because of their limited temperature range, the present datasets are unable to reveal the behavior of the contact parameter in low temperatures, and we are unable to fully validate the proposed function. We thus call for more heterogeneous nucleation experiments reaching low temperatures (<170 K). Such datasets may be significant for studies on, for example, polar mesospheric clouds, Mars ice clouds, and perhaps exoplanet clouds. This work provides a new framework, valid even for very small ice nucleus sizes, for analyzing heterogeneous nucleation datasets.

The morphology of a volcanic edifice reflects the integrated eruptive and evolutionary history of that system, and can be used to reconstruct the time-series of prior eruptions. We present a new high-resolution merged LiDAR-bathymetry grid, which has enabled detailed mapping of both onshore and offshore historic lava flows of the Kameni islands, emplaced in the centre of the Santorini caldera since at least AD 46. We identify three new submarine lava flows: two flows, of unknown age, lie to the east of Nea Kameni and a third submarine flow, located north of Nea Kameni appears to predate the 1925–1928 lava flows but was emplaced subsequent to the 1707–1711 lava flows. Yield strength estimates derived from the morphology of the 1570/1573 lobe suggest that submarine lava strengths are approximately two times greater than those derived from the onshore flows. To our knowledge this is the first documented yield strength estimate for submarine flows. This increase in strength is likely related to cooling and thickening of the dacite lava flows as they displace sea water. Improved lava volume estimates derived from the merged LiDAR-Bathymetry grid suggest typical lava extrusion rates of ∼2–3 m³ s⁻¹ during four of the historic eruptions on Nea Kameni (1707–1711, 1866–1870, 1925–1928 and 1939–1941). They also reveal a linear relationship between the pre-eruption interval and the volume of extruded lava. These observations may be used to estimate the size of future dome-building eruptions at Santorini volcano, based on the time interval since the last significant eruption.

We present a new Moho map for the Early-Proterozoic northwestern part of the Fennoscandian Shield, where the POLENET/LAPNET passive seismic array was located. The map is based on previously published and re-evaluated controlled source seismic data and P-wave receiver functions as well as new estimates of the Moho depth obtained by our analysis of P-wave receiver functions at broadband stations of the POLENET/LAPNET array. We estimated individual data quality for all input data and combined them into a new Moho map using CRUST3D software. The software seeks the simplest (smoothest) Moho surface that is consistent with all seismic data within their individual uncertainty limits. The new Moho map indicates that the crustal thickness in the study region varies between 42 km and 58 km, with the greatest thickness being reached in two separate areas in the northeast and the southeast. Two areas with relatively flat and shallow Moho, with an average Moho depth of c. 44 km, are located in the eastern and south-western parts of the study area. These two areas are separated by the Moho depression, with a maximum depth of 58 km. They can be associated with the Archean core of the Karelian craton and with the part of it that was reworked during the Early Proterozoic, respectively. A region with an average Moho depth of c. 47 km can be seen in the northern part of our study area, deepening to c. 55 km in the northeastern corner.

Most authors agree that parts of the Caribbean plate are an igneous Plateau underlain by Farallon lithosphere that was trapped in between the North and South American plates. However, the origin of the thickened crust is debated. The theory of oceanic plateaus forming as magmatic outpouring related to a plume arrival became prominent when Large Igneous Provinces could be traced back to hotspots. The present-day proximity of the Galapagos hotspot made it an obvious candidate for associating its plume head arrival with the formation of the Caribbean Plateau. However, it was shown that in a fixed or moving Indian-Atlantic hotspot reference frame, plate reconstructions predicted the Galapagos hotspot a thousand or more kilometres away from the Caribbean plate at the time of Plateau formation (∼88–94 Ma). Here, we calculate the goodness of fit for the Pacific hotspot reference frame and the recently developed Global Moving Hotspot Reference Frame. We show that both frames lead to good correlations between the paleo-positions of the Caribbean Plate and the Galapagos hotspot, when a docking time of the Caribbean plate to South America of 54.5 Ma is assumed. As this result is consistent with abundant evidence that lends support for a Galapagos hotspot origin of the rocks that form the Caribbean Plateau, proposed alternative mechanisms to explain the thickened crust of the Caribbean Plateau seem to be unnecessary. Finally, based on our model, we also derived an age distribution of the lithosphere underneath the thickened crust of the Caribbean Plateau.

The APSIS reactor has been designed to simulate in the laboratory with a VUV synchrotron irradiation the photochemistry occurring in planetary upper atmospheres. A $N_2''–''{\mathrm{CH}}_4$ Titan-like gas mixture has been studied, whose photochemistry in Titan’s ionospheric irradiation conditions leads to a coupled chemical network involving both radicals and ions. In the present work, an ion–neutral coupled model is developed to interpret the experimental data, taking into account the uncertainties on the kinetic parameters by Monte Carlo sampling. The model predicts species concentrations in agreement with mass spectrometry measurements of the methane consumption and product blocks intensities. Ion chemistry and in particular dissociative recombination are found to be very important through sensitivity analysis. The model is also applied to complementary environmental conditions, corresponding to Titan’s ionospheric average conditions and to another existing synchrotron setup. An innovative study of the correlations between species concentrations identifies two main competitive families, leading respectively to saturated and unsaturated species. We find that the unsaturated growth family, driven by $C_2{H}_2$, is dominant in Titan’s upper atmosphere, as observed by the Cassini INMS. But the saturated species are substantially more intense in the measurements of the two synchrotron experimental setups, and likely originate from catalysis by metallic walls of the reactors.