Timescales of geological processes: Preface

1.Introduction One of the major challenges in Geoscience is to understand how the formation and evolution of the Earth System are governed by timescales-that is,how the various geological processes that continue to contribute to its present-day structure and composition operated in the deep past.The traditional view of such processes refers to events that occur at immense spatial scales and over hundreds of millions of years,constrained in most cases by the ages of rocks determined using isotopic dating methods or the fossil record.However,the modern view of geological processes has increasingly acknowledged that their durations can be significantly shorter than previously thought possible,or indeed detectable without recent analytical innovations.Earthquakes are a prime example of rapid,high energy and episodic events that have a profound effect on subsequent processes such as metamorphism,fluid transport,and ore formation e the evidence of which is written in microstructures,compositional zoning,and P-T records.Experimental studies have also revealed that the reaction rates between fluids and rocks can be extremely rapid relative to geological timescales.This has led to the notion that geological processes are not necessarily continuous over millions of years but may,in fact,be sporadic,with long periods where essentially no reactions take place punctuated by periods of intense activity.

The Metamorphic Processes and Its Geological Implications of Gneisses from the Duoba Terrane of Xizang(Tibet) Plateau, China

A suit of metamorphic rocks experienced amphibolite and partly granulite facies metamorphism exposed on the Lhasa block,which are recognized as the basement of the Lhasa block named as Nyainqentanglha Group in the

Geological and surfacial processes and major disaster effects in the Yellow River Basin

The Yellow River Basin(YRB) is characterized by active geological and tectonic processes, rapid geomorphological evolution, and distinct climatic diversity. Correspondingly, major disasters in the YRB are characterized by varied types,extensive distributions, and sudden occurrences. In addition, major disasters in the YRB usually evolve into disaster chains that cause severe consequences. Therefore, major disasters in the YRB destroy ecologies and environments and influence geological and ecological safety in the basin. This paper systematically reviews research on geological and surface processes, major disaster effects, and risk mitigation in the YRB, discusses the trends and challenges of relevant research, analyzes the key scientific problems that need to be solved, and suggests prospects for future research based on the earth system science concept. Themes of research that should be focused on include geological, surface and climatic processes in the YRB and their interlinking disaster gestation mechanisms;formation mechanisms and disaster chain evolutions of giant landslides in the upper reach of the YRB;mechanisms and disaster chain effects of loess water-soil disasters in the middle reach of the YRB;occurrence patterns and amplifying effects of giant flood chains in the lower reach of the YRB;and risk mitigations of major disasters in the YRB. Key scientific problems that need to be solved are as follows: how to reveal the geological, surface and climatic processes that are coupled and interlinked with gestation mechanisms of major disasters;how to clarify the mutual feedback effects between major disasters and ecology;and how to develop a human-environmental harmony-based integrated risk mitigation system for major disasters. Prospects for future studies that follow the earth system science concept include the following: highlighting interdisciplinary research to reveal the interlinked disaster gestation mechanisms of the geology, surface and climate in the YRB in the past, present, and future;forming theories to clarify the regional patterns, dynamic mechanisms, and mutual-feedback effects between disaster chains and ecology in the YRB on land and in rivers in the region;solving technological bottlenecks to develop assessment models and mitigation theories for integrated risks in the YRB by following the human-environment harmony concept;and finally, establishing a demonstratable application pattern characterized by "whole-basin coverage" and "zonal controls", thereby guaranteeing ecological and geological safety in the basin and providing scientific support for ecological conservation and high-quality development of the YRB.

Geology of Mars after the first 40 years of exploration

The knowledge of Martian geology has increased enormously in the last 40 yr. Several missions orbiting or roving Mars have revolutionized our understanding of its evolution and geological features, which in several ways are similar to Earth, but are extremely different in many respects. The impressive dichotomy between the two Martian hemispheres is most likely linked to its impact cratering history, rather than internal dynamics such as on Earth. Mars＇ volcanism has been extensive, very longlived and rather constant in its setting. Water was available in large quantities in the distant past of Mars, when a magnetic field and more vigorous tectonics were active. Exogenic forces have been shaping Martian landscapes and have led to a plethora of landscapes shaped by wind, water and ice. Mars＇ dynamical behavior continues, with its climatic variation affecting climate and geology until very recent times. This paper tries to summarize major highlights in Mars＇ Geology, and points to deeper and more extensive sources of important scientific contributions and future exploration.

Probabilistic prediction of expected ground condition and construction time and costs in road tunnels

Ground condition and construction （excavation and support） time and costs are the key factors in decision-making during planning and design phases of a tunnel project. An innovative methodology for probabilistic estimation of ground condition and construction time and costs is proposed, which is an integration of the ground prediction approach based on Markov process, and the time and cost variance analysis based on Monte-Carlo （MC） simulation. The former provides the probabilistic description of ground classification along tunnel alignment according to the geological information revealed from geological profile and boreholes. The latter provides the probabilistic description of the expected construction time and costs for each operation according to the survey feedbacks from experts. Then an engineering application to Hamro tunnel is presented to demonstrate how the ground condition and the construction time and costs are estimated in a probabilistic way. In most items, in order to estimate the data needed for this methodology, a number of questionnaires are distributed among the tunneling experts and finally the mean values of the respondents are applied. These facilitate both the owners and the contractors to be aware of the risk that they should carry before construction, and are useful for both tendering and bidding.

PetroleumSystems of Chagan Depression,Yingen-Ejinaqi Basin, Northwest China

In order to further the course of petroleum exploration and development in the Chagan （查干） depression in the Yingen（银根）-Ejinaqi （额济纳旗） basin, Northwest China, the major characteristics of the petroleum systems were comprehensively analyzed, including the essential geological elements, processes, and oil characteristics. Petroleum system theory and quantitative simulation techniques were used. The dolomitic mudstone and shale of the Second Member of the Bayingebi （巴音戈壁） Formation are the major source rocks, with higher organic matter content and greater intensities of hydrocarbon generated and expelled. The sandstone in the First Member of the Suhongtu （苏红图） Formation is the main reservoir rock. The mudstone in the Second Member of the Suhongtu Formation is the most important seal. The crude oil discovered so far has a close relationship with the source rock in the Second Member of the Bayingebi Formation. There are three petroleum systems in the Chagan depression. The primary system is the Second Member of the Bayingebi Formation-the First Member of the Suhongtu Formation, which is the most important target for hydrocarbon exploration in the depression.

Integrating NLP and Ontology Matching into a Unified System for Automated Information Extraction from Geological Hazard Reports

Many detailed data on past geological hazard events are buried in geological hazard reports and have not been fully utilized. The growing developments in geographic information retrieval and temporal information retrieval offer opportunities to analyse this wealth of data to mine the spatiotemporal evolution of geological disaster occurrence and enhance risk decision making. This study presents a combined NLP and ontology matching information extraction framework for automatically recognizing semantic and spatiotemporal information from geological hazard reports. This framework mainly extracts unstructured information from geological disaster reports through named entity recognition, ontology matching and gazetteer matching to identify and annotate elements, thus enabling users to quickly obtain key information and understand the general content of disaster reports. In addition, we present the final results obtained from the experiments through a reasonable visualization and analyse the visual results. The extraction and retrieval of semantic information related to the dynamics of geohazard events are performed from both natural and human perspectives to provide information on the progress of events.

Structural analysis of rubble-pile asteroids applied to collisional evolution

Solar system small bodies come in a wide variety of shapes and sizes,which are achieved following very individual evolutional paths through billions of years.Nevertheless,some common mechanisms can still be found during these processes,e.g.,rubble-pile asteroids tend towards fluid equilibrium as they are reshaped by external disturbances.This paper focuses on the reshaping process of rubble-pile asteroids driven by meteorite impacts.A mesoscale cluster of solid spheres is employed as the principal model for a rubble-pile asteroid,for which little is actually known about their interior structure.We take this simple model as a rough guide to the qualitative aspects of the reshaping processes,and it can reveal,to some degree,the inner workings of rubble-pile asteroids.In our study,numerous possible equilibrium configurations are obtained via Monte Carlo simulation,and the structural stability of these configurations is determined via eigen analysis of the geometric constructions.The eigen decomposition reveals a connection between the cluster’s reactions and the types of external disturbance.Numerical simulations are performed to verify the analytical results.The gravitational N-body code pkdgrav is used to mimic the responses of the cluster under intermittent non-dispersive impacts.We statistically confirm that the stability index I S,the total gravitational potential P G,and the volume of inertia ellipsoid V E show consistent tendency of variation.A common regime is found in which the clusters tend towards crystallization under intermittent impacts,i.e.,only the configurations with high structural stability survive under the external disturbances.The results suggest the trivial non-disruptive impacts might play an important role in the rearrangement of the constituent blocks,which may strengthen these rubble piles and help to build a robust structure under impacts of similar magnitude.The final part of this study consists of systematic simulations over two parameters,the projectile momentum and the rotational speed of the cluster.The results show a critical value exists for the projectile momentum,as predicted by theory,below which all clusters become responseless to external disturbances;and the rotation proves to be significant for it exhibits an“enhancing”effect on loose-packed clusters,which coincides with the observation that several fast-spinning asteroids have low bulk densities.