Applications of Remote Sensing in Geology | Geology Optional Notes for UPSC PDF Download

Application of Remote Sensing in Geology

Overview

Remote sensing using multispectral sensors plays a crucial role in geology by aiding in the mapping of geomorphology, structure, and lithology. These maps find extensive use in various fields such as geoenvironmental appraisal, mineral exploration, and geotechnical projects. However, remote sensing is limited in areas with dense forest cover or other land types, as it primarily focuses on exposed rock structures like roadcuts and river sections. Validation becomes essential post-map preparation using remote sensing images.

Technological Advancements

• Technological advancements in sensor technology have significantly boosted the applications of remote sensing in geology.
• Hyperspectral images are particularly useful for lithological mapping based on mineralogy due to their ability to detect minerals based on spectral responses.
• Microwave sensors with side-looking imaging capabilities enhance the detection of geological structures.

Geological Mapping

• Identification of geological features based on spectral signatures helps in geological mapping.
• Satellite images require a solid geological background for interpretation and delineation of rocks.
• Remote sensing data offer a more efficient means of collecting information on geological structures compared to traditional mapping methods, thanks to their synoptic coverage and multispectral data.

Advantages of Remote Sensing

• Remote sensing provides a synoptic view of the terrain, enabling the visualization of the entire landscape and spatial relationships between different features.
• It offers valuable insights into geological structures and phenomena, supporting the field of geology with comprehensive data.

Remote Sensing in Geology

Exploration in Geology through Remote Sensing

Remote sensing in geology involves the exploration of minerals, studies in geological engineering, environmental geology, and analysis of geohazards.

Thermal Remote Sensing in Geological Mapping

• Thermal remote sensing is utilized for the discrimination of rock types and geological mapping.
• Rocks exhibit different thermal responses to temperature changes, with high thermal inertia rocks appearing brighter in nighttime images.
• Anticlines and synclines show distinct warmer and cooler signatures based on differences in thermal inertia.
• Weak zones like faults and fractures manifest as cool linear anomalies in both day and night thermal images.

Example: In a nighttime thermal image, rocks with high thermal inertia will appear brighter compared to rocks with lower thermal inertia.

Microwave Remote Sensing in Geological Mapping

• Microwave remote sensing, operating in the range of about 1 cm to 1 m, provides valuable information on surface roughness, complex dielectric constants, surface geometry, soil moisture, topography, and drainage patterns.
• Synthetic Aperture Radar (SAR) is used to capture this information, including details about in-situ rock types and sub-surface structures.

Example: SAR techniques offer relatively coarser resolution data that suppress minor variations, providing a broader view of geological terrain.

Lithological Mapping using Remote Sensing

• Remote sensing plays a crucial role in lithological mapping, which involves studying the physical characteristics of rocks.
• Spectral signatures of rocks are determined by the nature of parent elements and internal molecular structures.
• Various elements and compounds, such as Fe, Mn, Cu, Ni, Cr, hydroxyl ions, carbonates, and water molecules, exhibit distinctive signatures in different regions of the electromagnetic spectrum.

Example: Transitional metals like Fe and Mn are identified in the visible and near-infrared regions, while hydroxyl ions and carbonates are detected in the short-wavelength infrared region.

Recognized Reflected Region of the Electromagnetic Spectrum:

• Between 0.4-3.0 µm on the electromagnetic spectrum, there exists a recognized reflected region.
• Minerals in this range are detected using the thermal infrared region in various studies.

Structural Mapping Criteria using Remote Sensing Imagery

Geology

Attitude of Beds

• The attitude of a bed involves its dip direction, strike, and dip amount.
• Through analyzing slope asymmetry, landforms, and drainage characteristics, the dip amount can be determined using visual interpretation of satellite images.
• Example: Figure 2 displays a strike-slip fault seen on an aerial photograph near Los Vegas.

Folds

• Marker horizons mapping helps in identifying plunging, non-plunging, and refolded folds on satellite data.
• Criteria for fold recognition include the presence of parallel bedding in non-plunging folds.

Plunging Folds

• U-shaped outcrop patterns are observed in plunging folds. By determining the dip direction of beds, further classification into plunging anticlines or synclines can be made.
• Oval-shaped outcrop patterns are created by doubly plunging folds.

Linear Features

• Linear features in geological elements, such as lineaments representing joints, fractures, and faults, can be mapped using remotely sensed data.
• Identification of linear features involves considering factors like linearity, moisture content, vegetation distribution, pond locations, and linear stream segments.
• Interpreting faults is a challenging task, but by following specific principles, fault identification becomes feasible.
• Major streams curve around the nose of plunging folds, creating distinctive patterns.

Geological Mapping with Satellite Imagery

• Utilizing satellite imagery, geological features like lineaments can be mapped efficiently.
• Example: The ligament map illustrated in Figure 3 is derived from satellite imagery.

Key Terms and Techniques

• RGB 3-2-1 and FCC RGB 7-4-2 are color combinations used for imaging.
• PCA (Principal Component Analysis) aids in extracting relevant information from complex data sets.
• SRTM (Shuttle Radar Topography Mission) is a valuable tool for generating topographic data.
• Soble Filter is a technique used for edge detection in images.

Geomorphological Mapping

Overview

• Geomorphological mapping utilizes various approaches and scales due to its complexity.

Historical Methods

• In the past, ground surveys were the primary method, supplemented by topographic maps.
• Initially, aerial photographs from the 1970s were introduced for geomorphological mapping.

Technological Advancements

• With technological advancements, such as digital photogrammetric techniques, 3D landform analysis became feasible.
• Availability of high computing facilities further enhanced geomorphological studies.

Limitations

• Aerial photography has limitations in capturing dynamic morphological changes over time.

Advancements in Geomorphological Mapping

Satellite Technology

• Modern geomorphological mapping relies on satellite imagery for coverage of large regions.
• Satellite data can be collected from various sources like Landsat, SPOT, IRS, and others.

Usage of Satellite Data

• Landsat TM and MSS data are commonly used for mapping bathymetry, vegetation, soil, and rock formations.
• ERS and Radarsat data, utilizing microwave technology, are valuable for geological mapping.

Emerging Technologies

• DEM (Digital Elevation Model) is a new tool for both quantitative and qualitative geological mapping.
• DEM data derived from LIDAR and satellite imagery assist in analyzing geomorphic units.

Mapping Coastal Landforms

Techniques

• Image fusion and GIS (Geographic Information System) are employed in coastal landform mapping.

Study Object Selection Criteria

• A study object must be homogeneous and indivisible at the chosen scale.
• It should be defined based on genetic or structural patterns.

Geology and Its Applications

• Geological activities encompass various fields such as geo-environmental appraisal, mineral exploration, geo-engineering, geo-hazard assessment, groundwater studies, and geomorphic mapping.
• The Geological Survey of India conducts geomorphological mapping of the entire country on a 1:2,000,000 scale using Landsat MSS data.
• Nationwide resource mapping projects, including geomorphological mapping, are conducted by the Department of Space in collaboration with the National Remote Sensing Center.
• The systematic classification and mapping of geomorphic units on a 1:50,000 scale are carried out under the natural resource division of the National Remote Sensing Center.
• Remote sensing data products provide direct information about landscape features and surface characteristics, making the mapping of geomorphic units more efficient.

Mineral Exploration

Definition of Mineral Exploration

The process of identifying ores with commercially viable concentrations of minerals is referred to as mineral exploration. It involves intensive, organized, and professional investigation to locate these mineral deposits.

Role of Remote Sensing in Mineral Exploration

• Remote sensing data, characterized by synoptic, multispectral, and multi-temporal features, facilitates the rapid mapping of minerals.
• It helps in identifying altered areas, regions of hydrothermal activity, and zones of mineralization.
• High spatial and spectral resolution data obtained through remote sensing aids in the exploration, evaluation, and understanding of mineral deposits.
• The application of remote sensing in mineral exploration dates back around six decades. Initially, hand-held cameras on aircraft were used, evolving into sophisticated technologies such as satellite imagery and hyperspectral digital systems.
• Advancements in sensor technology allow for capturing narrow-band spectral signatures, enabling the identification of alteration minerals within deposits.
• Imaging spectrometers create continuous reflectance spectra due to their narrow spectral channels, facilitating the identification of minerals, especially in arid terrains using airborne hyperspectral data.

Stages of Mineral Exploration

• Area Selection: The initial stage involves choosing specific areas for exploration.
• Target Definition: This stage focuses on defining the specific targets within the selected areas.
• Resource Evaluation: Assessing the mineral resources found in the selected areas.
• Reserve Definition and Extraction: Determining the reserves and planning the extraction process.

Role of Remote Sensing in Different Stages

• During area selection and target definition, remote sensing is crucial in identifying spectral signatures of alteration zones associated with mineral deposits.
• Space-borne multispectral and hyperspectral sensors, as well as airborne hyperspectral scanners, play a significant role in detecting these spectral signatures.
• Knowledge of alteration zones and geological structures is essential for selecting areas and delineating targets during the mineral exploration process.

Geo-Engineering and Remote Sensing in Geology

Exploration for Mineral Deposits

• Prospecting for mineral deposits or suitable host rocks is crucial for identifying potential mineral reserves. Remote sensing data, in conjunction with geological maps, geochemical data, and geophysical data, is utilized to model mineral reserve potential.

Example: Using satellite imagery like the WorldView-3 SWIR data for mineral exploration.

Geo-Engineering

• The field of geology is multidisciplinary and has evolved over more than 200 years. The integration of multi-spectral remote sensing and Geographical Information Systems (GIS) has provided new tools for geological mapping.
• Geo-engineering involves applying engineering principles to geological studies, as geological factors influence the location, design, construction, operation, and maintenance of engineering works.

Example: Engineering geologists provide geological and geotechnical recommendations, as well as analysis and design services for construction projects.

• Critical Role of Remote Sensing: Remote sensing plays a significant role in engineering geology by offering valuable insights into geological features that impact engineering projects.
• Environmental Impact Analysis: Geoengineering involves assessing the environmental impact of engineering projects and incorporating measures to mitigate any negative effects.
• Construction Phase: During the construction phase, geoengineering ensures that engineering works are implemented according to geological and geotechnical recommendations.
• Value Engineering: Value engineering principles are applied to optimize the cost-effectiveness and efficiency of engineering projects within geological constraints.

Engineering Geology

Activities

• Engineering geologists conduct studies during public and private works projects, as well as in the post-construction and forensic phases.
• They investigate geological hazards, geotechnical aspects, material properties, landslides, slope stability, erosion, flooding, and seismic activities.
• The main goal is to protect life and property from damage by solving geological problems.

Site Selection

• Selection of suitable construction sites for structures like dams or tunnels involves considering factors such as lithology, geological structure, topography, and land use.
• Remote sensing and GIS techniques are crucial for integrating information for decision-making.

Feasibility Analysis

• Geoengineering allows for analyzing the feasibility of engineering structures.
• Construction and analysis of models like DEM (Digital Elevation Models) are essential for assessing structural stability and simulating impacts.

Environmental Geoscience

• Environmental geoscience is an interdisciplinary field that deals with environmental issues across various scientific disciplines.
• Remote sensing technology plays a key role in environmental surveillance, offering detailed analysis of environmental concerns.

Geo-Environmental Studies

• Remote sensing aids in the analysis of open-cast strip mining and land-use change.
• It helps in studying underground mining impacts like subsidence.

Applications of Remote Sensing

• Remote sensing technology provides multi-spectral, multi-temporal analysis of environmental issues.
• It is used to monitor and address land, water, air, and vegetation degradation.

Analysis of Dumping Grounds

• Release of smoke, thermal plumes, and air pollutants from industries, power plants, and their discharge.
• Discussion: Industries and power plants emit various harmful substances into the atmosphere during their operations, contributing to air pollution. For instance, factories release smoke containing particulate matter and greenhouse gases, while power plants emit thermal plumes that can affect the local environment.
• Problem of erosion and deforestation in the catchment of river and sediment loads.
• Explanation: The issue of erosion and deforestation in river catchment areas is a result of human activities like logging and agricultural practices. When trees are removed, soil becomes more vulnerable to erosion by water and wind, leading to sediment loads that can affect water quality and aquatic habitats.