Mountainous areas have become among the most developed areas of geological hazards due to special geological environmental conditions and intensive human engineering activities. Geological hazards are a main threat to urbanization, rural revitalization, and new rural construction in complex mountainous areas. It is of great strategic significance to conduct large-scale geological hazard investigation and risk assessment in urban areas, control the risk of geological hazards at the source and propose risk control measures. In this paper, we established the technical methods of geologic hazard risk assessment and control in complex mountain towns by taking Longlin Town in the mountainous region of Gansu Longnan, China as the study area, with the Quanjia bay debris flows and Panping Village landslides as the typical pilot investigation and assessment. The methods consist of six stages—risk identification, hazard disaster model investigation, risk analysis, vulnerability assessment, risk evaluation and risk management and control measures and proposals. On this basis, the results of geological hazards with different precipitation frequencies (5%, 2%, 1%) are presented. The results show that 75.23% of the regions remained at low risk levels; 24.38% of the regions increased a risk level with decreasing precipitation frequency, and 0.39% of the regions remained at extremely high risk levels under different precipitation frequency conditions. For the Quanjia bay debris flows and Panping Village landslides case, we discussed the geological hazards risk source control contents, management and control technologies, engineering and non-engineering measures of disaster prevention and control for urban disasters and specific disaster areas. This research can provide technical support and reference for disaster prevention and mitigation, and territorial spatial planning.

Ecological suitability evaluation is a critical component of regional sustainable development and construction, serving as a foundation for optimizing spatial patterns of regional growth. This is particularly pertinent in karst mountainous regions characterized by limited land resources and heightened ecosystem vulnerability, where a quantitative assessment of ecological suitability for land development is both crucial and urgent. Based on the fundamental principles of structural and functional dynamics in landscape ecology, this study focuses on Gui’an New Area, a designated urban development zone situated in the karst landscape of Guizhou Province. An index system was established encompassing three dimensions: ecological elements, ecological significance, and ecological resilience, utilizing the integrated ecological resistance (IER) model to evaluate the suitability of regional development and construction. The results reveal that the eastern region exhibits higher suitability compared to the central and western regions, with the northwest region demonstrating the lowest suitability overall. Relatively speaking, the evaluation of geological environment suitability and the comprehensive ecological constraints associated with development and construction indicates that the areas currently planned and ongoing reflect flat terrain and low ecological risk. Furthermore, within the scope of ecosystem dynamic adaptation, developmental activities in these regions exert minimal impact on the natural ecosystem, thereby demonstrating a high suitability for development and construction. In terms of future key development zones, areas with gentle slopes ranging from 8 to 15 degrees are recommended, aligning with the actual requirements for cultivated land protection. The total area designated as prohibited development zones constitutes the smallest proportion, representing only 9.45%, which is significantly lower than that of priority development zones (38.75%) and moderate development zones (22.45%). From the perspective of landscape ecology, this paper provides a comprehensive investigation into the ecological suitability evaluation system for development and construction in the karst regions of Southwest China, offering valuable insights for assessing ecological suitability in similar areas.

Taking the Lijiapo landslide in Three Gorges Area as an example, the study on the impact of seepage field changes caused by water level fluctuation on reservoir landslide stability was carried out. In order to find out the variation in slope stability when the reservoir water level changes at different rate, the stability calculation model was established adopting the Seep module and Slope module of Geoscience software GeoStudio, and calibrated with a long sequence of real-time monitoring data, based on the landslide survey data and test data. The results show that the reservoir landslide stability affected by the seepage field changes with changing reservoir level is controlled by a variety of factors, including the hydrodynamic pressure, hydrostatic pressure, uplift force, physical and mechanical properties (с, φ value change). When the water level fluctuates at a high rate, the impact of the seepage field changes on the stability is mainly affected by the pore water pressure before the stability reaches the extremum, while after the extremum, with the further infiltration or drainage of reservoir water, it is mainly affected by the change of physical and mechanical properties. When the water level fluctuates at a lower rate, the pore water pressure, uplift force and physical and mechanical properties are the dominant factors.

Whether the northern margin of the North China Craton (NCC) was a continental arc or in a lithospheric extensional setting during the Carboniferous is the primary divergence among different tectonic models about the terminal evolutionary history of the southeastern Central Asian Orogenic Belt (CAOB). The Alxa block is the western segment of the northern NCC and contiguous to the southeastern CAOB, and therefore the tectonic setting of the Carboniferous magmatic intrusions in this block can shed light on this controversy. In this contribution, new zircon U–Pb ages, elemental geochemistry, and Sr-Nd isotopes are presented for thirteen Late Carboniferous (~318–300 Ma) magmatic intrusions in the southwestern Alxa block. Among them, seven calc-alkaline I-type granites and one aluminous A2-type granite were probably generated by the partial melting and crystallization differentiation of various crustal sources (perhaps including earlier orogenic materials) under different temperature conditions. Four quartz diorites and one hornblende gabbro may be the partial melts of subduction-modified basaltic lower crust sources and sub-continental lithospheric mantle sources, respectively. According to the integration of the new results and regional geological correlations, the Alxa block and the southeastern CAOB were most likely in a uniform tectonic regime during the Carboniferous. At that time, this region was characterized by the lithospheric extension-related magmatic rock associations, the increasing mantle inputs over time, the clockwise P–T paths of high temperature-low pressure metamorphic rocks, and the transgression sedimentary sequences. All these lines of evidence suggest an intra-continental lithospheric extensional setting rather than a continental arc setting for the southeastern CAOB during the Carboniferous.