The major fields in GEOLOGY are mineralogy, petrology, sedimentology, geochemistry, geomathematics, stratigraphy, palaeontology, structural geology, economic geology, petroleum geology, mining geology, structural geology, marine geology, engineering geology, geomorphology, hydrogeology, environmental geology and geoscience education. GEOPHYSICS is often regarded as a separate Earth Science discipline. Check out the links at left to find out more about each of these Earth Science Disciplines.

GEOLOGY

The primary objective of the science of geology is to understand the processes by which the planet earth was formed, the evolution of the continents and seas, and the origins of the materials within the earth’s crust—the igneous, sedimentary and metamorphic rocks and their minerals.

PETROLOGY

Petrology is the study of rocks—the minerals that they are composed of, and the textures and other features that provide clues about how the rocks formed. It is subdivided into sedimentary, igneous and metamorphic petrology. This is because the processes under which sedimentary, igneous and metamorphic rocks form are quite different and require different skills in their study. Sedimentary petrology is the study of the mineral composition of sedimentary rocks, mainly as a guide of where on the earth’s crust the rocks originated. Igneous petrology involves the study of magmas and the processes which give rise to varying compositions and textures of intrusive and extrusive igneous rocks. Metamorphic petrology concentrates on how rocks of all kinds can be changed by heat and pressure within the Earth’s crust into metamorphic rocks. MINERALOGY is the study of the minerals themselves—their chemical composition and crystal forms—for which a background in chemistry is desirable

SEDIMENTOLOGY AND VOLCANOLOGY

Sedimentology and volcanology are closely allied fields that examine rocks at outcrop and larger scales, with the aim to unravel the geological history of a reasonably large area—ancient volcanoes, or river valleys, or entire sedimentary basins. Sedimentology is devoted to the study of rock sequences laid down as sedimentary rocks by water, wind or ice, whereas Volcanology studies the results of eruptions of igneous rocks. Volcanic eruptions involve the passage of large volumes of hot fluids rich in metallic minerals through the earth’s crust so that the study of volcanology is an important component of Economic Geology.

STRATIGRAPHY

Stratigraphy is the study of the composition, ordering and relationships of rock strata in order to determine their geological history. It was one of the first disciplines in Geology and remains one of the most important skills. Principles such as the law of superposition, recognition of erosional breaks (unconformities) and cross-cutting relationships are peculiar to geology. The stratigrapher must understand the individual events that have resulted in the rock formations as they occur today. Many of the other disciplines (Palaeontology, Sedimentology, Volcanology, Structural geology, Geochronology) are used by the stratigrapher.

PALAEONTOLOGY

Palaeontology is the systematic study of animal/plant fossil remains. At its core is the principle that organisms evolve, and that the changes wrought by evolution can be used to determine the age of the fossil and its host rock. The last 500 million years of earth’s history (known as the Phanerozoic) has been divided into very fine subdivision on the basis of this principle, with the fine subdivisions named after the fossils that are found in it. Age determination and correlation (using the same fossil to date rocks in different places, often at a global scale) remain one of the most important services that palaeontologists provide. Palaeontology is also used to help identify where sedimentary rocks have been laid down (e.g. in a river, or near a seashore) and can help determine the nature of biological provinces that result from the migration of continents. A knowledge of biology is a good start for budding palaeontologists. Specialists studying plant fossils are called PALAEOBOTANISTS. MICROPALAEONTOLOGISTS and PALYNOLOGISTS study fossilised microscopic animal remains, spores, pollens and certain other microfossils. Both fields are particularly useful in petroleum exploration. Palaeontologists need to use their studies of fossils to interpret the PALAEOECOLOGY and PALAEOCLIMATOLOGY i.e. the environmental conditions in which the fossils were laid down. Most palaeontologists are employed by museums, mining companies specialising in oil, coal and limestone and universities.

STRUCTURAL GEOLOGY

Structural geology is the study of structures in rock formations that were caused by deformation of any kind, usually due to folding or faulting. It has become increasingly important over the last few decades as it has proved to be a powerful tool in elucidating the overall history of regions and continents. It is an important component of global studies on the movement and formation of the earth’s tectonic plates—PLATE TECTONICS. It is also one of the most important disciplines in the study of mineral deposits in determining the influence of structure on the formation, distribution and geometry of deposits of metallic ores, petroleum and coal.

TECTONICS

Tectonics is the study of large-scale structures of the earth such as mountain ranges, sedimentary basins, continents and oceans. This field of study utilises many of the other disciplines of geology, such as structural geology, petrology, stratigraphy, geochemistry, marine geology and geophysics. Most earth scientists use the theory of PLATE TECTONICS to explain the origin of continents and oceans, the current distribution of earthquakes, volcanoes, mountain ranges and rift valleys, and to determine the past distribution of landmasses and seas. Knowledge of tectonics helps in the discovery of ore bodies and petroleum deposits.

GEOCHEMISTRY

GEOCHRONOLOGY

The study of the radioactive decay of isotopes that occur naturally in some minerals, with the aim to determine the absolute age of a rock. Geochronology also includes other methods of age determination, such as fission track studies and solar irradiation studies.

ECONOMIC GEOLOGY

PETROLEUM GEOLOGY

MINING GEOLOGY

Involves working in an operating mine or quarry to accurately survey the progress of operations in respect of geological structure, sample mineral or rock to obtain assays to determine whether economic grade or yield is being maintained; design and supervise exploration programs ahead of production to maintain reserves. Mine geologists need to have a broad knowledge of earth sciences as well as general knowledge of mining engineering, metallurgy and mineral economics.

GEOMATHEMATICS

Geomathematics is a very diverse field that arises from the need for measurement, whether it be from field measurements of rock structures, to the statistical analysis of mineral aggregates on a microscopic slide, or to magnetic or gravity measurements in geophysics, or to the need to graph or derive equations to explain or predict from these measurements. A good training in mathematics, statistics and computing is vital.

MARINE GEOLOGY

Marine geology is the application of earth science studies to modern marine environments. Specialised ships are used as a platform for drilling the sea bed and for undertaking seismic studies. Marine Geology is used in the study of PLATE TECTONICS and in oil and gas exploration. In recent years Marine Geology has been applied to the exploration for rich sea-floor massive sulphide deposits of gold, silver, copper, zinc and lead. Mining of these deposits remains some years off, however. Marine Geology expeditions often utilise specialists in Sedimentology, Palaeontology, Geophysics, Economic Geology and Petrology.

ENGINEERING GEOLOGY

Engineering geology involves the study of the stability and structure of the materials of the Earth’s crust in particular reference to the foundations of man-made structures such as roads, bridges, tunnels, freeways, dams, power stations, and large buildings. A good knowledge of the stratigraphy and geological structure of the local area is necessary, as well as the physical and chemical characteristics of the foundation materials. The nature and movement of underground waters is also necessary as an essential component of such studies. The continual expansion of cities requires prior studies of landforms by geologists to assess whether land is susceptible to landslides, unstable foundation materials or whether development will lead to pollution of valuable sources of surface or underground water. Coastal areas are particularly susceptible to ill-considered developments. GEOTECHNICAL ENGINEERING makes such studies available to architects and engineers.

GEOMORPHOLOGY

Geomorphology is the study of landforms from the interplay of constructional and destructional forces acting on the Earth’s surface. It involves study of the erosional and depositional work of water, wind, ice and gravity as well as the constructional influences of earth movements and volcanoes. It is an important aspect in the study of the geological history of a region, especially in Australia where erosional forces have been a dominant influence for a long time. A Geomorphologist needs to understand Stratigraphy, Petrology, Geochemistry and Palaeoclimatology. An important skill gained by those trained in Geomorphology is aerial photo interpretation, the ability to identify the rock types and their history from aerial photographs. Geomorphology is needed for tourism in national parks, and in the study of physical geography and PLANETARY GEOLOGY.

HYDROGEOLOGY

Hydrogeology is an increasingly important area of Earth Science. It is the study of groundwaters including the location and nature of water-bearing layers (aquifers) and structures in geological formations. The role of Hydrogeologists is to plan drilling programs and use geophysical techniques to locate water supplies and assess their quality and yield for towns and cities, mining and agriculture projects. Another important function is to protect water resources from overdevelopment and pollution from industrial and domestic disposal of waste materials. The issue of groundwater salinity is set to become an increasingly serious problem throughout inland Australia. Hydrogeologists will play a vital part in understanding and addressing this problem. By identifying and mapping salt-water reservoirs before they erupt at the surface, hydrogeologists will provide catchment managers with the raw data required to manage groundwater aquifers

ENVIRONMENTAL GEOLOGY

Environmental geology incorporates branches of Earth Sciences such as Hydrogeology and Engineering Geology to address the demands of conservation and environmental protection. Environmental Geology relates to the operation of mines, quarries and other industrial facilities, their impact on the environment and the eventual reclamation of their sites. Industrial and domestic waste disposal is an area that increasingly requires detailed Environmental Geology studies to prevent pollution of surface and underground waters.

GEOPHYSICS

Geophysics is often regarded as a distinct field of study different from Geology. It combines a knowledge of physics and geology in analysing the physical characteristics of the materials in the Earth’s crust. Highly sophisticated instruments and techniques are used to measure a wide range of properties. These include magnetism, radioactivity, electrical conductivity, rock density, seismic variations, heat flow, spectral properties (light wavelengths reflected by different minerals), radar reflectivity and others. Many of these are important in various branches of economic geology. Earthquake hazards provide an important impetus to seismic studies. A sound training in physics and mathematics is essential for those wanting to tackle this rewarding discipline.