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Geological Investigations

Geological investigations can be split into two parts: Field and Laboratory studies. Unlike other branches of science, experiments in the strict sense of the word are not possible in geology. Geoscientists have advocated mechanisms like Plate Tectonics to explain the generation of magma, causes of earthquakes, and so on.

Field Studies

Field studies are a crucial methodology in geology, entailing the conduct of geological observations, measurements, and sampling in the field to collect data and elucidate the Earth’s internal structure and external environment. Through field-based geological research, we can gain insights into geological processes, geological structures, mineral resources, and environmental issues, thereby enhancing our understanding of the Earth’s complex systems and phenomena.

Components of Field Studies and Field Methods

Field studies involve collecting data, which is plotted on topographical maps, and documenting the data. The two main components of field studies are:

• The first component: Topographical maps, aerial photographs, and satellite imageries are used to gather information about the rocks and geomorphological features.
• The second component: Instruments such as clinometer compass, pocket lens, penknife, dil. HCl, sample bags, and camera are used to collect data in the field. Typical fieldwork could consist of:
  • Geological mapping: identifying the locations of major rock units and the faults and folds that led to their placement there.
  • Structural mapping: identifying the locations of major rock units and the faults and folds that led to their placement there.
  • Stratigraphic mapping: pinpointing the locations of sedimentary facies (lithofacies and biofacies) or the mapping of isopachs of equal thickness of sedimentary rock.
  • Surficial mapping: recording the locations of soils and surficial deposits.
  • Surveying of topographic features: compilation of topographic maps, work to understand change across landscapes, including patterns of erosion and deposition, and hillslope processes.
  • Subsurface mapping through geophysical methods: shallow seismic surveys, ground-penetrating radar, aeromagnetic surveys, electrical resistivity tomography, and other methods to aid in hydrocarbon exploration, finding groundwater, and locating buried archaeological artifacts.
  • High-resolution stratigraphy: measuring and describing stratigraphic sections on the surface, well drilling and logging.
  • Biogeochemistry and geomicrobiology: collecting samples to determine biochemical pathways, identify new species of organisms, and identify new chemical compounds.
  • Paleontology: excavation of fossil material for research into past life and evolution.
  • Collection of samples for geochronology and thermochronology: collecting samples to determine the age and thermal history of rocks.
  • Glaciology: measurement of characteristics of glaciers and their motion.

Specific Tools and Their Uses

• Clinometer compass: measures bearings, dip, and direction of structural elements.
• Pocket lens: identifies minerals in hand specimens.
• Penknife: tests hardness and streak of minerals.
• Dil. HCl: confirms presence of carbonate minerals.
• Sample bags: collects fragile materials or fossils.
• Camera: documents field settings and special features.

Laboratory Investigations

Laboratory investigations are used to strengthen the observations made during field studies. Laboratory studies involve megascopic and microscopic examinations, chemical analysis of rock samples, and other tests. The goal of laboratory investigations is to provide more detailed information about the composition, structure, and properties of rocks, which can help to refine the interpretations made during field studies.

Components of Geological Map

A geological map consists of two components: petrographical (rocks) and structural features. The petrographical component documents different rock types, while the structural component documents structural features such as faults, joints, and folds.

Investigative Methods

Geologists use various methods to understand Earth history and processes, including:

• Petrology: study of rocks
• Structural geology: study of the orientation and arrangement of rocks and their internal structures
• Stratigraphy: study of the layering of rocks and the relationships between different rock units
• Geophysics: study of the physical properties of the Earth, including its gravity, magnetic, and seismic properties
• Biogeochemistry and geomicrobiology: study of the interactions between living organisms and the Earth’s geochemical cycles
• Paleontology: study of fossils and ancient life forms

Data Collection During Mapping Exercise

During a mapping exercise, geologists collect various types of data, including:

• Rock specimens: samples of rocks collected from the field
• Petrographic data: information about the composition and structure of rocks
• Igneous rocks: rocks that form from the cooling and solidification of magma
• Sedimentary rocks: rocks that form from the accumulation and compression of sediments
• Metamorphic rocks: rocks that form from the alteration of existing rocks under high pressure and temperature conditions
• Structural data: information about the arrangement and orientation of rocks and their features, including:
  • Planar structures: features such as bedding planes, foliation, and fractures
  • Linear structures: features such as folds, faults, and lineations
• Data for petrofabric studies: information about the orientation and distribution of minerals and other components within rocks, which can help to reconstruct the rock’s history and evolution.