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Geology Definition, History, and Branches

Definition

Geology (in Greek, Geo means Earth, Logos means Science) is a branch of science that deals with Earth study. It is also known as earth science. This is a very simple definition for something so complex. Geology involves studying the materials that make up the earth, the features, and structures found on Earth as well as the processes that act upon them. Geology also deals with the study of the history of all life that’s ever lived on or is living on the earth now. Studying how life and our planet have changed over time is an important part of geology.

in other words, is the scientific study of the Earth, including the materials that it is made of, the physical and chemical processes that occur on its surface and in its interior, and the history of the planet and its life forms.

History

Geology has been of interest to humans as far back as ancient Egyptian history, where the enormous amount of stone material worked and moved, partly over long distances, during ancient Egyptian history still remains admirable if one considers that it was mined during a time interval of almost three thousand years. Stone was the most important raw material used during the different periods of Pharaonic Egypt until Greco-Roman and Arab times.

In ancient Greece (the 4th century). Aristotle was one of the first people to make observations about the earth. This was also the first time that scientists and philosophers noted a difference between rocks and minerals. The Romans became very adept at mining certain rocks for use in building their empire, especially marble.

In the 17th century, fossils were being used as a way to understand what happened to the earth over time. These fossils played a key role in the debate about the age of Earth. For a while and even in some cases today, theologians and scientists have been at odds about the age of Earth. Theologians believed Earth was only about 6,000 years old while the scientists believed it to be much older.

In the 18th century, scientists started focusing on minerals and mineral ores since mining was an important part of global economies. During this century, two main theories came forward explaining some of the physical features of the earth. One theory believed that all rocks were deposited by the oceans during flooding events. The second theory believed that some rocks were formed through heat or fire.

This debate continued into the 19th century until James Hutton proved that some rocks are formed by volcanic (heat & fire) processes and others are formed by sedimentation. Hutton also explained that all the processes we see going on today, are the same processes that happened in the geologic past and that they occurred very slowly.

In other words, the erosion that is occurring to our mountains today is the same process that eroded mountains in the past. This theory became known as Uniformitarianism, which simply stated says ‘the present is the key to the past.’ James Hutton is known as the Father of Modern Geology.

Once Uniformitarianism was accepted by the scientific community, all the geologic pieces started to fall into place. Geologists began to understand how fossils could help them date the earth and different rock layers called strata. The fossils acted as markers that allowed geologists to place them in order of occurrence, allowed them to correlate rock strata found over great distances, and helped them understand the changes in life over time and the changes in Earth’s environment through time.


The next big leap for geology happened in the early 1900s. A scientist, Alfred Wegener proposed a theory called Continental Drift. Wegener suggested that the continents moved around on the surface of the earth and came together to form a supercontinent known as Pangaea.

Ocean Floor Eruption

Ocean Floor Eruption

Ocean Floor Eruption

Ocean Floor Eruption

Tectonic Plates

Tectonic Plates

Tectonic Plates

Tectonic Plates

He cited several pieces of evidence to prove his theory, the continents all fit together like puzzle pieces, the same rock unit or fossil could be found on both sides of an ocean and similar features such as mountains could be found on continents when they were all together.

He suggested that continents ‘floated’ or ‘drifted’ to their positions. However, he could not explain how this happened. The scientific community rejected his theory until the 1940s. The technology boom associated with WWII brought advances in sonar and radar. In 1947, two geologists mapped the ocean floor, which revealed evidence that oceanic crust is created at mid-ocean ridges.

This became known as seafloor spreading. These mid-ocean ridges, are found on the bottom of the oceans and are major cracks or vents in oceanic crust. Magma from the mantle pushes its way up through the cracks (think of squeezing toothpaste from its tube). As it does this, it pushes the existing crust causing continents to move around. This led to the Theory of Plate Tectonics, which is based on the idea that Earth is broken into tectonic plates and these plates move in response to seafloor spreading.

Imagine taking a hard-boiled egg and dropping it on the floor. The egg cracks all around. The areas between the cracks are called plates and the cracks are called boundaries. The same principle applies to the earth. If we could shake off all the water on the planet so we could see the ocean floor, we would be able to see these cracks and boundaries.

Some Branches of Geology

Different branches of geology study one particular part of the earth. Since all of the branches are connected, specialists work together to answer complicated questions.

  • Geochemistry: Geochemistry is the study of the chemical processes which form and shape the Earth. It includes the study of the cycles of matter and energy which transport the Earth’s chemical components and the interaction of these cycles with the hydrosphere and the atmosphere.

It is a subfield of inorganic chemistry, which is concerned with the properties of all the elements in the periodic table and their compounds. Inorganic chemistry investigates the characteristics of substances that are not organic, such as nonliving matter and minerals found in the Earth’s crust.

  • Oceanography: Oceanography is the study of the composition and motion of the water column and the processes which are responsible for that motion. The principal oceanographic processes influencing continental shelf waters include waves and tides as well as wind-driven and other oceanic currents. Understanding the oceanography of shelf waters and the influence this has on seabed dynamics, contributes to a wide range of activities such as the following:
    1. Assessment of offshore petroleum production infrastructure.
    2. Seabed mapping and characterization for environmental management.
    3. Marine biodiversity surrogacy research.
    4. Assessment of renewable energy potential.
  • Paleontology: Paleontologists are interested in fossils and how ancient organisms lived. Paleontology is the study of fossils and what they reveal about the history of our planet. In marine environments, microfossils collected within in layers of sediment cores provide a rich source of information about the environmental history of an area.
  • Sedimentology: Sedimentology is the study of sediment grains in marine and other deposits, with a focus on physical properties and the processes which form a deposit. The deposition is a geological process where geological material is added to a landform. Key physical properties of interest include:
    1. The size and shape of sediment grains.
    2. The degree of sorting of a deposit.
    3. The composition of grains within a deposit.
    4. Sedimentary structures.

These properties together provide a record of the mechanisms active during sediment transportation and deposition which allows the interpretation of the environmental conditions that produced a sediment deposit, either in modern settings or in the geological record.

Additional Branches:

  • Benthic Ecology: Benthic ecology is the study of living things on the seafloor and how they interact with their environment.
  • Biostratigraphy: Biostratigraphy is the branch of stratigraphy that uses fossils to establish relative ages of rock and correlate successions of sedimentary rocks within and between depositional basins.
  • Geochronology: Geochronology is a discipline of geoscience which measures the age of earth materials and provides the temporal framework in which other geoscience data can be interpreted in the context of Earth’s history.
  • Geophysics: Information relating to various techniques including airborne electromagnetics, gravity, magnetics, magnetotellurics, radiometric, rock properties, and seismic.
  • Marine Geochemistry: Marine geochemistry is the science used to help develop an understanding of the composition of coastal and marine water and sediments.
  • Marine Geophysics: Marine geophysics is a scientific discipline that uses the quantitative observation of physical properties to understanding the seafloor and sub-seafloor geology.
  • Marine Surveying: The survey environment varies from oceanographic studies in the water column to investigating sediment and geochemical processes on the seafloor and imaging the sub-seafloor rocks. Surveys are carried over Australia’s entire marine jurisdiction, from coastal estuaries and bays, across the continental shelf and slope, to the deep abyssal plains.
  • Spectral Geology: Spectral geology is the measurement and analysis of portions of the electromagnetic spectrum to identify spectrally distinct and physically significant features of different rock types and surface materials, their mineralogy, and their alteration signatures.

Another Classification for Geology

1- Physical Geology

Physical geology deals with the Solar system, the Earth’s origin, age, internal constitution, weathering, mass-wasting, and geological work of river, lake, glacier, wind, sea, and groundwater. It also deals with the Volcanoes – their types & distribution, geological effects, and products; earthquakes -their distribution, causes, and effects. Physical Geology also projects the elementary ideas about the origin of geo synclines, the concept of isostasy and mountain building (Orogeny), continental drift, seafloor spreading, and plate tectonics. This subject gives the foundation for all other earth science branches.

2- Historical geology

Historical geology is the discipline that uses the principles and techniques of geology to reconstruct and understand the past geological history of Earth. It is a major branch that deals with the records of events of earth’s history and with the historical sequence and evolution of plants and animals of past ages. Its object is to arrange the events of earth’s history in the regular chronological order of their occurrence and to interpret their significance. Fortunately, the historical records are preserved in the layered rocks of the crust. Historical Geology is, sometimes called Strati graphical Geology. It brings together all collated details of other Branches of Geology like Paleontology, petrology, and structural geology, pertaining to age-wise correlated beds.

3- Geomorphology

Geomorphology is the scientific study of the origin and evolution of landforms and landscapes created by physical, chemical, or biological processes operating at or near the Earth’s surface. It is concerned with the internal geologic processes of the earth’s crust, such as tectonic activity and volcanism that constructs new landforms, as well as externally driven forces of wind, water, waves, and glacial ice that modify such landforms. It is closely related to soil science, hydrology, geology, and environmental science. This has the potential for applications in environmental / development planning, transport, human settlements, mining and hydrological sectors, hospitality, and tourism.

Geomorphology also focuses on the investigation of surface processes and the way these processes create small-scale landforms.

3.1 Evolutionary Geomorphology

Which deals with the Davisian Erosion Cycles / peneplain (Footprints of Darwinian Evolution).

3.2 Process Geomorphology

The study of the processes responsible for landform development.

3.3 Quantitative Dynamic Geomorphology

Drainage basin morphology (stream order, density etc.) Newtonian mechanistic approach (stream power, fluvial erosion, diffusion/transport laws, Dynamic equilibrium approach d) Thermodynamic Geomorphology – Entropy concept.

3.4 Predictive Geomorphology

Earth cast (extreme events – flood, landslide) – Mathematical morphology (Fractal, Spatio-temporal Geoscience Information System analysis) – Deterministic & Numerical models – Artificial Neuron Network (ANN).

3.5 Planetary geomorphology

Planetary geomorphology is yet another branch of geomorphology. It involves the study of landforms on planets and their satellites. It is a modern branch. Most of the surface processes on other planets and their satellites depend on various factors like mean distance from the Sun, annual receipt of solar energy, rotational period, and on the nature of the planetary atmospheric conditions. Observed geomorphic processes include weathering, wind activity, fluvial activity, glacial activity, and mass wasting.

3.6 Tectonic geomorphology

Tectonic geomorphology is the study of the interplay between tectonic and geomorphic processes in regions where the Earth’s crust actively deforms. Tectonic geomorphology is the study of the interplay between tectonic and surface processes that shape the landscape in regions of active deformation. Recent advances in the quantification of rates and physical basis of tectonic and surface processes have rejuvenated the field of tectonic geomorphology. Modern tectonic geomorphology is an exciting and highly integrative field which utilizes techniques and data derived from studies of geomorphology, seismology, geochronology, structure, geodesy, and Quaternary climate change. While emphasizing new insights from the last decade of research, Tectonic Geomorphology reviews the fundamentals of the subject which include the nature of faulting and folding, the creation and use of geomorphic markers for tracing deformation, chronological techniques which date deformation, geodetic techniques for defining recent deformation, and paleo-seismologic approaches to calibrate past deformation. Tectonic geomorphology is an integrated subject that presents stimulating challenges to anyone trying to extract information from deforming landscapes.

3.7 Fluvial geomorphology and river management.

Fluvial geomorphology is the scientific study of the forms and functions of streams and the interaction between streams and the landscapes that evolve around them. Fluvial geomorphology is an applied science. It is mainly devoted to understand the development of rivers, both in their natural setting as well as on how they respond to the anthropogenic changes imposed within a watershed.

3.8 Coastal geomorphology

The scientific study of the morphological development and evolution of the coasts. Coastal landforms are developed under the influence of winds, waves, currents, and sea-level changes. This branch focuses on the physical processes and their responses in the coastal zone. It is also an applied science. Sustainable management of coastal resources requires a detailed knowledge on coastal zones.

3.9 Tropical geomorphology.

The tropics are a typical climatic region. They are characterized by particular climates that may be dry or humid. The tropics can be divided into two primary units based on annual rainfall, the humid tropics and the arid topics. These are the belts of low latitudes and high temperature. Like climate, landforms and operating geomorphic processes are not the same across the tropics. The tropics are an assemblage of active tectonic belts, ancient cratons, alluvial valleys and subsiding deltas. Geomorphology in the tropics provides twin opportunities to discover new facts and to apply such information to manage the environment for a sustainable future. Tropical geomorphology has a tendency to look forward rather than look back exclusively at past landforms. Relative to temperate zones, the tropics contain areas of high temperatures, high rainfall intensities and high evapotranspiration, all of which are climatic features relevant for surface processes.

3.10 Glacial geomorphology

Concerned principally with the role of glacial ice in landform and landscape evolution. It is the scientific study of the processes, landscapes, and landforms produced by ice sheets, valley glaciers, and other ice masses on the surface of the Earth. These processes include understanding how ice masses move, and how glacial ice erodes, transports, and deposits sediment. This subject is much useful to the planetary geologists who are interested in understanding the evolution and history of the surface of nearby planets in our solar system. It has been reported that the planet Mars is covered with permafrost, where the soil temperatures are permanently below the freezing point of water. Bitter cold temperatures dominate the Martian equatorial regions, with an annual-mean temperature of the soil colder than -50 deg C, and colder still at middle and high latitudes. Therefore, any water present in the Martian soil must be in the form of ice. Glacial deposits form characteristic flow features that indicate thick piles of water ice in a slow viscous motion.

3.11 Periglacial Geomorphology

Periglacial geomorphology must also be viewed as one of the group of sciences that concern the cryosphere. Periglacial geomorphology has a special interest in the thawing and freezing of ground. The core of periglacial geomorphology is concerned with the study of freezing processes, associated with ground ice, and their related landforms. Such an approach places permafrost in a central position, within periglacial geomorphology. This subject primarily focuses on the geomorphological processes and landforms associated with glaciers, permafrost, and periglacial and slope environments. Periglacial environments are characterized by frost action and the recurrent presence of a snow cover. The salient components of modern periglacial geomorphology include the study of i) the nature of permafrost-related processes, ground ice, and associated landforms; ii) the a zonal processes that operate in cold non-glacial environments; iii) the ice-marginal (proglacial) environment and associated paraglacial transitions; iv) the alpine (montane) environment; v) Pleistocene cold-climate paleo-environmental reconstructions; vi) environmental and geotechnical studies associated with frozen ground, ground freezing and global climate change.

3.12 Climatic Geomorphology

The study of the role of climate in shaping landforms and the earth-surface processes. An approach used in climatic geomorphology is to study relict landforms to infer about the ancient climates. It is mainly concerned about the past climates. Climatic geomorphology identifies climatic factors such as the intensity, frequency and duration of precipitation, frost intensity, direction and power of wind, and it explains the development of landscapes under different climatic conditions. Since landscape features in one region might have evolved under certain specific climate, different from that of today, studying climatologically distinct regions of the past might help to understand the present-day landscapes.

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