Geology and Geological Engineering
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PermafrostPermafrost, or perennially frozen ground, is defined as soil or rock having temperatures below 0oC over at least two consecutive winters and the intervening summer. Much of the permafrost has been frozen since the Pleistocene time. Permafrost occurs in the Arctic, Antarctic and high alpine regions. About one-fifth of the total land area of the world is underlain by permafrost (Burdick et al. 1978). The top layer of the ground in which the temperature fluctuates above or below 0oC during the year is defined as the active layer (Andersland and Ladanyi 1994). Other terms such as seasonally frozen ground, seasonal frost and annually thawed layer are synonyms for the active layer. The thickness of this layer varies spatially and temporally. The upper boundary of permafrost is defined as the permafrost table. In the discontinuous permafrost zone, taliks form between the active layer and the permafrost table. Taliks, or unfrozen ground, are layers of ground that remain unfrozen throughout the year (Andersland and Ladanyi 1994). In the continuous permafrost zone, taliks often occur underneath shallow thermokarst lakes or rivers, where the water below a certain depth may not freeze in winter and, thus, the soil underneath will not freeze either. Other terms, such as thaw lake or cave-in lake, have also been used for a thermokarst lake. Open talik is an area of unfrozen ground that is open to the ground surface but otherwise enclosed in permafrost. Through talik is unfrozen ground that is exposed to the ground surface and to a larger mass of unfrozen ground beneath. Unfrozen ground encased in permafrost is known as a closed talik.
Aeromagnetic surveyAn aeromagnetic survey (AMS) is an air-borne geophysical survey performed using a magnetometer aboard or towed behind an aircraft. A magnetometer is an instrument used to measure the magnetic field. Aeromagnetic surveys are probably one of the most common types of air-borne geophysical surveys. The applications of AMS in engineering geology include, but are not limited to, near-surface geological mapping, structural geology mapping, aiding three-dimension (3D) geological subsurface model construction, groundwater study, environmental study, and geologic hazards assessment. In an aeromagnetic survey, an airplane, flying at a low altitude, carrying a magnetic sensor flies back and forth in a grid-like pattern over an area, recording disturbances in the magnetic field (Fig. 1). Height and gridline spacing determine the resolution of the data. Geologic processes often bring together rocks with slightly different magnetic properties, and these variations cause very small magnetic fields above the Earth’s surface. The differences in the magnetic field are called “anomalies.” (Blakely et al. 1999).
GIS for natural resources (mineral, energy, and water)Natural resources embrace a broad array of categories, including agricultural, conservational, forestry, oceanic, water, energy, and mineral resources. This chapter only focuses on the latter three. Traditional methods for natural resource management include, but are not limited to, geophysical exploration, field geological mapping, geochemical analysis, and aero-photo interpretations. Natural resource related research is by nature a spatial problem. Integration of field survey data and other pertinent information can be a time-consuming task by traditional ways. With the help of GIS, most of the tasks can be conducted in ways that are nearly impossible in traditional methods. Three case studies of GIS application in natural resource analyses will be presented in this book chapter to demonstrate the GIS applications in compiling, integrating, analyzing and visualizing natural resource data.
GIS for earth sciencesGeographic Information System (GIS) supports data collection, geospatial data analysis, visualization, scientific communication and research collaboration. GIS has implications for many fields of the Earth Sciences, which are about and beyond one’s imagination. Since the development of the first computerized GIS in the 1960s, the need by professionals for geospatial technology in fields that utilize geospatial data has never stopped expanding. As noted by a market analysis in August 2017: “The GIS Market was valued at USD 5.33 Billion in 2016 and is expected to reach USD 10.12 Billion by 2023, growing at a compound annual growth rate of 9.6% between 2017 and 2023.” (marketsandmarkets.com, August 2017). Earth Sciences encompasses a broad and diverse array of technical areas, such as geology, geomorphology, geography, geophysics, hydrology, hydrogeology, environmental sciences, oceanography, meteorology, and atmospheric sciences. All of these fields are using geospatial data to solve complex problems related to the planet Earth. Some of these problems are nearly impossible to solve without the use of GIS. This article presents a brief introduction to GIS and examples of its applications to the Earth sciences. Three case studies highlight the utility of GIS applications in compiling, integrating, analyzing and visualizing geospatial data.
U-Pb geochronology of monazite from a carbonatite dike and hydrothermally altered pegmatite dike in the Wet Mountains, ColoradoU-Pb Laser Ablation-Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) isotopic data were collected for igneous and hydrothermal monazite from a carbonatite dike and hydrothermally altered pegmatite dike, respectively, to determine the age of carbonatite emplacement and rare earth element (REE) mineralization in the Wet Mountains, Colorado. Fifty analyses from three monazite grains from each sample yielded reliable 206Pb/238U data. Sample locations were recording using a handheld Global Positioning System.