Defining patterns of environmental or ecological change on different spatio-temporal scales is key to tracking and addressing present and future biodiversity changes, which is particularly important considering the rapidly changing climate scenarios. Climate change in the arctic means shrinking glaciers, drying out of peatland and carbon release, more frequent forest and peatland fires, and thawing permafrost. Alaska hosts some of the largest Boreal peatlands and forests; however, little is known about the fine-scale dynamics of these ecosystems particularly over the last millennia, which is key to making effective management decisions into the uncertain future. In this presentation, I will be presenting the results so far from an ongoing work that employs different lines of evidence (pollen, non-pollen palynomorphs, charcoal, and tephra) from two peatland sites in southern Alaska to reveal interactions between vegetation, fire and climate in the area during the last millennia, as well as the potential influence of humans and volcanic eruptions on these interactions.

The Atacama Desert is the oldest and driest non-polar desert on Earth, where salts have accumulated through atmospheric deposition over millions of years of hyperaridity. These salts can serve as an indicator to provide an understanding of the interaction between water and soil in changing environmental conditions. Therefore, four soil profiles were studied for their mineralogy, abundance of salts, and stable isotopic composition of sulfate. In all soil profiles, sulfates are the predominant salts showing a downward transition from gypsum to anhydrite accompanied by an increase in highly soluble salts and a decrease in δ³⁴S and δ¹⁸O values of sulfate. These trends are consistent with downward water infiltration during rare rain events causing salt dissolution and subsequent precipitation in the deeper soil column. This conclusion is also supported by our Rayleigh fractionation model. The presence of anhydrite at >40 cm depth is attributed to their association with nitrate and chloride salts, which reduces water activity during sulfate precipitation and thus stimulates anhydrite formation. Along the elevation transect, the total salt inventories of the individual profiles show a tendency for nitrate and chloride concentrations to decrease with elevation. This observation, together with the stable isotopes of sulfate, suggests a fog-independent source and points to the remobilization of soluble salts by enhanced erosion of the hillslopes. These findings are essential for understanding pedogenetic processes and long-term regional habitability of hyperarid environments.

In recent decades varies extremophiles were found deep in the lithosphere. Experimental studies showed that life is possible at 121 °C (Takai et al. 2008) and the gigapascal range (Sharma et al. 2002), which is beyond the p-T-range of the investigated lithosphere. Knowledge on the kinetic stability of vital molecular compounds, like ATP, can help us constraining the conditions possible for life.

All metabolism relies on the exergonic enzymatic hydrolysis of adenosine triphosphate (ATP) to adenosine diphosphate (ADP). At elevated temperatures, the enhanced kinetics of the non-enzymatic hydrolysis counteracts the enzymatic driven reaction; hence, it will limit the bioavailability of ATP.

We used an autoclave and a hydrothermal diamond anvil cell attached to a Raman spectrometer for in-situ investigation of the p-T-X-effects on the kinetics of the non-enzymatic ATP hydrolysis. At vapor pressure the half-lives were about 2-5 mins at 120 °C (Moeller et al. 2022). Up to 140 MPa, all results show an Arrhenian relationship in the T-range of 80-120 °C. The pressure effect can be best described by a power law; below 500 MPa the p-effect is vanishingly small, and above the rate constant increases exponentially. Addition of MgCl₂ up too 4 wt% slows down the hydrolysis. A distinguished effect of NaCl and CaCl₂ was not observed.

The proposed limit for ATP-based life of 195 °C by Moeller et al. (2022) is lowered by additional pressure or elevated by MgCl₂, respectively. These observations strengthen the idea that life could exist far deeper in the lithosphere as discovered yet.

Two granitic plutons are exposed at Dubair and Shang in the vicinity of Besham, northern Pakistan, in the northwestern part of the Indian plate. Both granitoids mainly consist of perthitic feldspar, plagioclase, and quartz together with minor biotite, amphibole, and accessory ilmenite, apatite, titanite, and zircon. They are peraluminous and alkali-calcic to alkaline in composition, with strong A-type affinity (Ahmad et al., 2021). La-ICP-MS U-Pb dating and trace element analysis of zircon from both plutons were performed to elucidate their emplacement ages and temperatures. Most of the zircons are characterized by oscillatory zoning, depletion in light REE, and enrichment of heavy REE, with pronounced positive Ce and negative Eu anomalies. U–Pb zircon dating of the Shang and Dubair granitoid reveals similar concordant Palaeoproterozoic ages of 1871± 8.1 Ma and 1862 ± 7.5 Ma, respectively. The calculated Ti-in-zircon temperatures mainly range between 800°C and 900°C. The U-Pb ages, zircon compositions, and high magmatic temperatures suggest solidification of the granitoids from a crustal-derived magma emplaced during the Paleoproterozoic.

Reference

Ahmad, T., Arif, M., Qasim, M., & Sajid, M. (2021). Petrology of granitoids from Indus syntaxis, northern Pakistan: Implications for Paleo-Proterozoic A-type magmatism in north-western Indian Plate. Geochemistry, 81(1), 125693.

The seismic signature of landslides preserves information of utmost importance in reconstructing the impact forces induced by landslides and, subsequently, the trajectory of motion and the dynamic properties of the sliding mass. Several studies focusing on large-scale events successfully inverted the source-time function and, therefore, the time-varying force exerted on the surface from the observed low-frequency (<0.1 Hz) seismic waves recorded in the far field. Nonetheless, most landslide events are small in terms of the displaced mass, which is more likely to excite rapidly attenuating seismic waves. With dominant frequencies above 1 Hz, these waves are noticeable only at the stations near the landslide. Analyzing the seismic signal generated by landslides in the near field is challenging. The proposed models would require a thorough description of the ground propagation medium, which is only available for some study cases. Here, we investigate using analytical solutions to Lamb’s problem to simulate the propagation history of the surface waves during the April 2022 Guanyuan landslide, Taiwan. This landslide mobilised more than 100,000 m³ of rock and stopped the traffic on the Taiwanese Central Cross-Island Highway for 43 days. The proximity of the landslide to a broadband station located about 6 km away allows the study of the near-field seismic signals. The duration and amplitude of the force retrieved in this fashion agree with qualitative observations, suggesting the potential of the model to extract source characteristics of landslides from seismic signals recorded in the near field.

Tsunamis generated by submarine or coastal landslides are a growing area of scientific interest. Events like the 2018 tsunami in Palu, Indonesia, have highlighted their destructive potential. Landslides can generate extremely high tsunami waves, but typically have a limited propagation range beyond 100 km. Areas close to the landslide are most affected. Unfortunately, early warning systems are not effective for this type of tsunami due to the short warning time interval between wave initiation and coastal impact.

This study aims to analyze the coastal and submarine landslide susceptibility for coastal areas. Limited data availability, including high-resolution bathymetric data and historical landslide tsunami catalogs, poses a major challenge. A heuristic model is used, incorporating historical case studies to calibrate and weight the parameters. Geologic, morphologic, and geometric parameters of coastal areas are considered.

First results show a high correlation of landslides generated during the Palu earthquake with the size of catchment areas of rivers entering the ocean. This parameter is strongly related with the sediment load that is transported into the ocean. High sedimentation rates might lead to the formation of thick, unconsolidated sediment layers., which are susceptible to landslides. This correlation will be further analyzed.

The results of this susceptibility mapping can help raise the awareness of the risks associated with landslide tsunamis. Even minor earthquakes, not expected to trigger tsunamis, could induce submarine or nearshore landslides and generate a tsunami in vulnerable areas. Consequently, adapting tsunami evacuation strategies to account for landslide-induced tsunamis may be required in these areas.