Reviewer in Geology

Module 1:

Geology is the scientific study of the all constituents of planets, their internal and external forms and processes. More precisely, it is the study of nature, structure and history of the planet. Earth is the home to all life, well known to the humankind. Geology, itself, is a major part of The Earth and atmospheric sciences, which were born as twins .

Geologists are the scientists who study the origin, occurrence, distribution and utilities of all materials (metallic, nonmetallic, inorganic, etc), minerals, rocks, sediments, soils, water, oil and all other inorganic natural resources.

The word "Geology" is derived from the Greek word "geo" means globe and "logos" means logical discourse.

The subject of Physical geology deals with the study of Earth's materials, such as minerals and rocks, as well as the processes that are operating on and within the Earth and on its surface.

The subject of Historical geology focuses on the origin and evolution of life on the Earth, its continents, oceans, atmosphere, and the life of all ecosystems.

Branches of Geology

-MAIN BRANCHES

1. Economic Geology

2. General Geology

3. Geotectonics

4. Historical Geology

5. Minerology

6. Paleonotology

7. Structural Geology

ALLIED BRANCHES

1. Engineering Geology

2. Environmental Geology

3. Geochemistry

4. Geophysics

5. Hydro-geology

6. Marine Geology

Economic Geology is the scientific study of the Earth’s sources of mineral raw materials and the practical application of the acquired knowledge.

Engineering geology is the application of the geology to engineering study for the purpose of assuring that the geological factors regarding the location, design, construction, operation and maintenance of engineering works are recognized and accounted for.

Geotectonic is a subject of earth science which deals with the phenomena of solid earth on a global scale and the timescale of the earth’s history.

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 which deals with the records of events of earth history and with the historical sequence and evolution of plants and animals of past ages.

The history of mineralogy is as old as humankind. Minerals have been an important part of our society since the time of prehistoric man. Mineralogy is the branch of geology concerned with the study of minerals.

Paleontology or palaeontology is the scientific study of the developing history of life on earth. It is the study of ancient plants and animals based on their fossil record. It is a fact that the evidence of existence of all life on earth, since the origin, are mostly preserved in rocks.

Structural geology is the scientific study of the three-dimensional distribution of rock units with respect to their deformational genesis and histories. The primary goal of structural geology is to use measurements of present-day rock geometries to uncover the information about their origin and history of deformation (strain) in the rocks.

Environmental geology, like hydrogeology, is an applied science concerned with the practical application of the principles of geology in the solving of environmental problems. It is a multidisciplinary field that is closely related to engineering geology and, to a lesser extent, to environmental geography.

Geochemistry is a branch that uses the tools and principles of chemistry to explain

the mechanisms behind major geological systems such as the Earth's crust and its oceans.

The realm of geochemistry extends beyond the Earth, encompassing the entire Solar

System .

Geophysics is a major subject of natural science. It is a core branch of geology. It is concerned with the physical processes and physical properties of the Earth and its surrounding space environment, and the use of quantitative methods for their analysis. The term geophysics sometimes refers only to the geological applications: Earth's shape; its gravitational and magnetic fields; its internal structure and composition; its dynamics and their surface expression in plate tectonics, the generation of magmas, volcanism and rock formation.

Major Branches of Geophysics

1. Geophysics- study of how plants, microbial activity and other organisms alter geologic materials and affect geophysical signatures.

2. Exploration geophysics- the use of surface methods to detect concentration of ore minerals and hydrocarbons.

3. Geophysical fluid dynamics- study of large-scale flows on Earth and other planets.

4. Geodesy- measurement and representation of the Earth, including its gravitational field.

5. Geodynamics- study of modes of transport deformation, mantle convection, heat flow, and lithosphere dynamics.

6. Geomagnetism- study of Earth’s magnetic field, including its origin, telluric currents driven by the magnetic field, the Van Allen belts, and the interaction between the magnetosphere and the solar wind.

7. Mathematical geophysics- development and application of mathematical methods and technique for the solution of geophysical problems.

8. Mineral physics- science of materials that compose the interior of planets, particularly the earth.

9. Near-surface geophysics- the use of geophysical methods to investigate small-scale features in the shallow (ten of meters) subsurface.

10. Paleomagnetism- measurement of the orientation of the earth’s magnetic field over the geologic past.

11. Seismology- study of the structure and composition of the earth through seismic waves, and of surface deformation during earthquakes and seismic hazards.

12. Tectonophysics- study of the physical processes that cause and result from plate tectonics.

Module 2:

EARTH STRUCTURE AND COMPOSITION

Core, mantle, and crust are divisions based on composition.

The crust makes up less than 1 percent of Earth by mass, consisting of oceanic crust and continental crust is often more felsic rock.

The mantle is hot and represents about 68 percent of Earth’s mass.

The core is mostly iron metal.

The core makes up about 31% of the Earth.

The lithosphere is composed of both the crust and the portion of the upper mantle that behaves as a brittle, rigid solid.

The asthenosphere is partially molten upper mantle material that behaves plastically and can flow.

• CRUST; a cold, thin, brittle outer shell made of rock.

There are two very different types of crust, each with its own distinctive physical and chemical properties.

1. Oceanic crust is composed of magma that erupts on the seafloor to create basalt lava flows or cools deeper down to create the intrusive igneous rock gabbro.

2. Continental crust is made up of many different types of igneous, metamorphic, and sedimentary rocks.

• Mantle

The two most important things about the mantle are:

1. it is made of solid rock, and

2. it is hot

Scientists know that the mantle is extremely hot because of the heat flowing outward from it and because of its physical properties.

Heat flows in two different ways within the Earth:

1. Conduction- is defined as the heat transfer that occurs through rapid collisions of atoms, which can only happen if the material is solid.

2. Convection- is the process of a material that can move and flow may develop convection currents. Convection in the mantle is the same as convection in a pot of water on a stove.

• Core

Calculations indicate that the CORE is about 85 percent iron metal with nickel metal making up much of the remaining 15 percent.

Metallic meteorites are thought to be representative of the core.

Scientists know that the outer core is liquid and the inner core is solid because S-waves stop at the inner core.

• ELEMENTARY KNOWLEDGE ON CONTINENTAL DRIFT AND PLATE TECTONICS

In 1855, Antonio Snider went so far as to publish a sketch showing how the two continents could fit together, jigsaw-puzzle fashion. Such reconstructions gave rise to the bold suggestion that perhaps these continents had once been part of the same landmass, which had later broken up.

Wegener began to publish his ideas in 1912 and continued to do so for nearly two decades. He proposed that all the continental landmasses had once formed a single supercontinent, Pangaea (Greek for “all lands”), which had then split apart, the modern continents moving to their present positions via a process called continental drift.

Tectonics is the study of largescale movement and deformation of the earth’s outer layers.

Plate tectonics relates such deformation to the existence and movement of rigid “plates” over a weaker, more plastic layer in the earth’s upper mantle.

• PLATE TECTONICS - UNDERLYING CONCEPT

-major obstacle to accepting the concept of continental drift was imagining solid continents moving over solid earth.

-The existence of plates, and the occurrence of earthquakes in them, reflect the way rocks respond to stress.

• STRESS AND STRAIN IN GEOLOGIC MATERIALS

-under stress when force is being applied to it.

-The stress may be compressive, tending to squeeze or compress the object, or it may be tensile, tending to pull the object apart.

-Shearing stress is one that tends to cause different parts of the object to move in different directions across a plane or to slide past one another, as when a deck of cards is spread out on a tabletop by a sideways sweep of the hand.

Strain is deformation resulting from stress. It may be either temporary or permanent, depending on the amount and type of stress and on the physical properties of the material.

If elastic deformation occurs, the amount of deformation is proportional to the stress applied, and the material returns to its original size and shape when the stress is removed.

reek word lithos, meaning “rock.”

The layer below the lithosphere is the asthenosphere, which derives its name from the Greek word asthenias, meaning “without strength.”

The asthenosphere was discovered by studying the behavior of seismic waves from earthquakes.

• LOCATING PLATE BOUNDARIES

-The distribution of earthquakes and volcanic eruptions indicates that these phenomena are far from uniformly distributed over the earth.

-They are, for the most part, concentrated in belts or linear chains.

-This is consistent with the idea that the rigid shell of lithosphere is cracked in places, broken up into pieces, or plates.

-The volcanoes and earthquakes are concentrated at the boundaries of these lithospheric plates, where plates jostle or scrape against each other.

• PLATE TECTONICS - ACCUMULATING EVIDENCE

-Through the 2Oth century, geologists continued to expand their knowledge of the earth, extending their observations into the ocean basins and applying new instruments and techniques, such as measuring magnetism in rocks, or studying the small variations in local gravitational pull that can provide information about geology below.

• TOPOGRAPHY OF THE SEA FLOOR

- Those who first speculated about possible drifting continents could not examine the seafloor for any relevant evidence. Indeed, many assumed that the sea floor was simply avast, monotonous plain on which sediments derived from the continents accumulated.

• MAGNETISM IN ROCKS

-The rocks of the ocean floors are rich in ferromagnesian minerals, and such minerals

are abundant in many rocks on the continents as well. Most iron-bearing minerals are at

least weakly magnetic at surface temperatures. Each magnetic mineral has a Curie

temperature, the temperature below which it remains magnetic, but above which it loses

its magnetic properties. The Curie temperature varies from mineral to mineral, but it is

always below the mineral’s melting temperature.

• WHY DO PLATES MOVE ?

-A driving force for plate tectonics has not been identified. For many years, the most widely

accepted explanation was that the plates were moved by large convection cells slowly

churning in the plastic asthenosphere.

• MOVEMENTS BETWEEN PLATES

Movement patterns of Motions of plate :

Collision - When two continental plates are shoved together.

Subduction - When on plate plunges beneath another.

Spreading - When two plates are pushed apart

Transform Faulting - When two plates slide past each other.

MODULE 3:

• EARTH PROCESSES

-The study of earth processes is based on number of fundamental principles, some of which are unique. The earths topographic features are a mixture of land forms being formed at the present time and others that have been shaped in the past by processes no longer active, it embraces the investigation of both the mechanics of modern processes and the historic influence of geologic time.

The surface processes responsible for most of the earth’s topographic features are:

1. Weathering- describes the breaking down or dissolving of rocks and minerals on the surface of the Earth. Water, ice, acids, salts, plants, animals, and changes in temperature are all agents of weathering.

2. Mass wasting- is the movement of rock and soil down slope under the influence of gravity. Rock falls, slumps, and debris flows are all examples of mass wasting. Often lubricated by rainfall or agitated by seismic activity, these events may occur very rapidly and move as a flow.

3. Running water- These processes are primarily driven by the movement of water, typically through rivers, streams, and other water bodies. Read here to learn about the erosional landforms by running water and groundwater.

4. Ground water- is a part of the natural water cycle (check out our interactive water cycle diagram). Some part of the precipitation that lands on the ground surface infiltrates into the subsurface. The part that continues downward through the soil until it reaches rock material that is saturated is groundwater recharge.

5. Glaciers- are massive bodies of slowly moving ice. Glaciers form on land, and they are made up of fallen snow that gets compressed into ice over many centuries. They move slowly downward from the pull of gravity

6. Waves- form when the wind blows over a body of water. In the open ocean waves look like a series of swells. When a wave gets near the shore the wave bottom drags against the sea floor while the top keeps moving. The wave gets narrower and higher and eventually topples over crashing onto the beach face.

7. Wind- is a powerful agent of erosion. Aeolian (wind-driven) processes constantly transport dust, sand, and ash from one place to another. Wind can sometimes blow sand into towering dunes.

8. Tectonism- Tectonic processes cause the movement of land and earthquakes. This heat drives plate tectonics and parts of the rock cycle. Where humans can live can be affected by volcanic events, sea level rise, and earthquakes, all of which are related to tectonic processes.

9. Volcanism- -Is the eruption of molten rock from inside the Earth to the surface. Volcanism occurs because of Earth’s internal heat, and is associated with tectonic processes and a part of the rock cycle.

Earth’s surface is a dynamic interface across which the atmosphere, water, biota, and tectonics interact to transform rock into landscapes with distinctive features crucial to the function and existence of water resources, natural hazards, climate, biogeochemical cycles, and life. Interacting physical, chemical, biotic, and human processes “Earth surface processes” alter and reshape Earth’s surface on spatial scales that range from those of atomic particles to continents and over time scales that operate from nanoseconds to millions of years

EVOLUTION OF LANDFORMS

Landforms evolve with time through a continuous sequence of forms having typical features at successive stages of development, largely as a result of continuous changes in processes and rates as time goes on.

MONITORING EARTH SURFACE PROCESSES AT HIGH RESOLUTION IN SPACE AND TIME

The evolution and increasing availability of new measurement technologies has enabled many of the advances in Earth surface processes. Technological advances in remote sensing, geochemistry, geochronology, and computing have fostered great progress in the study of Earth’s surface

• WEATHERING

Weathering- is the breakdown of rocks at the earth’s surface by the action of rainwater, extremes of temperature, and biological activity. It does not involve the removal of rock material.

There are three types of weathering:

1. PHYSICAL WEATHERING - It is due to physical effects like temperature, abrasion, wedging action of ice, penetration of plant roots etc.

-Physical weathering results no change in chemical composition of particles

It produces coarsed grained and non cohesive soils (examples gravel and sand)

1. CHEMICAL WEATHERING- It is due to chemical actions (oxidation, hydration, carbonation, solution, leaching, hydrolysis etc.)

-Original rock minerals are transformed into clay minerals.

-It results in fine grained and cohesive soil (example:clay)

BIOLOGICAL WEATHERING- Is caused by the movements of plants and animals.

-For example, a rabbit can burrow into a crack in a rock making it bigger and eventually splitting the rock, or a plant may grow in a crack in a rock and, as its roots grow, cause the crack to widen.