Carbonate petrography is the study of limestones, dolomites and associated deposits under optical or electron microscopes greatly enhances field studies or core observations and can provide a frame of reference for geochemical studies.
Of these various reasons, faulting related to plate movements is by far the most significant. In other words, most earthquakes are due to slip on faults.
As stated earlier, no one locality on Earth provides a complete record of our planet’s history, because stratigraphic columns can contain unconformities. But by correlating rocks from locality to locality at millions of places around the world, geologists have pieced together a composite stratigraphic column, called the geologic column, that represents the entirety of Earth history.
Geometry of Folds Imagine a carpet lying flat on the floor. Push on one end of the carpet, and it will wrinkle or contort into a series of wavelike curves. Stresses developed during mountain building can similarly warp or bend bedding and foliation (or other planar features) in rock. The result a curve in the shape of a rock layer is called a fold.
Igneous rocks are those formed by the direct cooling of magma or lava. Magma or lava is the molten form of rocks where intense heat turns them into hot magma. This is semi fluid and is in the subsurface. This magma can come out and produce lava and this also intrude in the joints or into the parent rock which is called dykes or sills. Igneous rocks are of two types according to the place where they forms i.e. intrusive and extrusive.
Intrusive
Intrusive rocks are those which are formed in the subsurface by direct cooling of the magma with overburden pressure. These rocks cools down gradually thereby giving time for minerals forming larger crystals. These are also called plutonic rocks. Intrusive rocks possess greater hardness than that of the volcanic rocks, this is because of the gradual cooling example are Granite, Gabbro and Peridotite.
Extrusive
Extrusive or volcanic rocks are formed by the lava when it erupts from the subsurface. As in the open air and release of overburden pressure they cools rapidly and produces smaller crystals. The examples of volcanic rocks are Rhyolite, volcanic glass and many more.
Metamorphic rocks are formed by the heating of pre-existing rocks. The heat provide to a rock changes it mineralogical and physical changes which are called metamorphic rocks.
These rocks forms mostly where magma chamber is available to heat enough for mineralogical changes occurrence. These rocks have multiple features in distinguishing like schistosic, gneissic and slaty texures.
Texture is the physical character or a pattern.
Slaty texture
Slate are formed by the metamorphism of shale. Sheets are formed in the slates where it can broke into sheets. This help in determining the slates.
Schistose
Schistose is formed after metamorphism of slate where it rearrange in forming irregular sheets like character which is schistosic texture.
Gneissic
Gneiss is the high grade metamorphic rock of shale which is distinguished by regular interval of dark and light bands present in it. These are called gneissic bands which is the recognizable character.
Metamorphism and its changes are following
Shale- Slate- Schist - Gneiss
Shale is sedimentary rock when metamorphose produces slate and slate to schist and schist to gneiss with increasing metamorphic grades. In the same way marble is produced by the metamorphism of limestone.
Sedimentary rocks are those which are made up of pre-existing small particles called sediments. There are two types of sedimentary rocks
clastic
non clastic
Clastic
Clastic rocks are those which are made up of sediments that are transported from other places. The sediment supply to the deposition are can be by the help of wind, gravity, water or ice. These rocks have many examples including sandstone and shale. The sandstone are made up of grains clustered together by the means of cements. Cement is the mineral that hold rock together, not splitting them in finer grains. Cement in the sandstone are silica or calcite. The sand particles are carried to the depositional area with the help of wind, an example of desert or the rivers deposits with the help of water. The grains are suspended either in the water or wind and when both medium speed breaks it can not carry the weight so are then deposited. It takes million years in order to the deposited sediments to form a rock as it needs pressure which can be overburden. It forms a rock which is called clastic rock.
Non clastic
Non clastic rocks are those which deposits at the area of origin. These sediments are not reworked by trasporting agents but are thus deposited where it have been formed or at lesser distance travel. These are also formed by the weathering process but not the erosional process. The best example of non clastic rocks are coral reefs. Corals habitat is colonial so when they die, deposits at its origin place. Limestone can also be formed clastically when the shells are reworked by turbiditic currents and drops calcium carbonate shells from shallow marine to deeper portion but eventually that won't be non clastic.
Weathering is the dissemination, destruction or breaking of the rock to finer particles. Weathering occur by many means, it can be either chemical, organic or mechanical.
Chemical weatheing
Chemical weathering occurs by the ion exchange method, dissolution of some particles which breaks the bond and the rock is thus weathered. The rock is dissolved when it is acid rain and the rock weathers. the best example in understanding chemical weathering is water dissolving limestone producing Karst topography. This help in the building of sedimentary rocks by erosion. Erosional means are wind, gravity, ice and water. When sediments are eroded it deposits at some other place, builds sedimentary rocks
Organic weathering
Organic as the name indicates is done by organisms. Plant roots break rock when they move into the rock and so the weathering process occurs.Rock is first weakened by penetrating forces of roots and thus split into smaller and smaller pieces. These are then eroded.
Mechanical weathering
Mechanical weathering is the physical breaking of a rock by means of force. The best example of the mechanical weathering is the permafrost. The water enters the pores and joints of a rock and when it freezes at low temperature areas. As the property of water at freezing is expansion so the water in rocks expands which widens the spaces and after some time disintegrated.
The deposition of these sediments occur when wind, water or ice slows in speed and have no capacity to blow away the particles, it deposits.
Sedimentary rocks are those that are produced by the deposition of sediments (small particles). The sediments cluster and are cemented that produces a rock. Sedimentary rocks are also called soft rocks as they are not produced by heat factor but are produced by the weathering of the rocks that are exposed on the Earth surface.
Metamorphic rocks
Metamorphic rocks are those which minerals are changed by heat not directly magma but heat which does not melt it but only changes the mineralization.
Igneous rocks
Igneous rocks are those which are produced by the direct melting rocks (magma). The magma cooling in the subsurface are called plutonic or intrusive rocks and those lava cooling on the surface are the volcanic or extrusive rocks.
The rock cycle changes the rocks from one form into another.
Petroleum is basically the fossil fuel. Hydrocarbon C and H are the components that make up different types of fuel example oil, gas and coal. Well the generation of hydrocarbon type is given by a specific type of Kerogen.
Kerogen
Kerogen is the organic matter that are deposited, it can be made up of different types. Example micro-organism, sea plants, land plants etc.
Different type of Kerogen produces different type of hydrocarbon
Type I Kerogen
This type of Kerogen comprises organic matter of microorganisms which is mostly from sea, they settle down at the bottom of the sea when they die and deposit. These type gives mostly oil and less gas.
Type II Kerogen
This comprises mostly of the sea plants and less animal so they care to generate oil and gas but mostly gas and less oil.
Type III Kerogen
This has the terrestial (land) plants and as you know coal is formed by the remains of plants so type 3 gives coal and less oil and gas comparative higher proportion.
Type IV Kerogen
This type of kerogen is oxidized and in order for the hydrocarbon generation the organic matter should not be oxidized or they will not produce the fuel. So the type 4 give inert gases as organic matter is oxidized and produce less gas, not economical.
Structure Geology as the name indicates it is related to structures. What kind of structures are to be observed in this field?. The basic structures that is often used are
Faults
Folds
Faults
Faults are defined as the displacement or the movement in the rocks that make up the Earth's crust.
Figure 1. Fault in the Earth's crust.
As shown in the figure 1 the arrows indicate the movement of the rocks, the movement is referred as comparative movement. there are different types of fault's as further divided by the way of displacement. The block that moves relative to another is the hanging-wall and the block which is static at it's position is the foot wall. The foot wall can Move upward and downward. So the fault as divided are by this movement. When hanging-wall moves downward with respect to action of gravity of the above burden it is called normal fault. And the hanging wall upward movement is called reverse fault as is against the gravity. The major division of the faults are strike-slip and dip-slip Strike slip faults are along strike so in order to understand the strike slip 1st strike should be known. Strike is the line which is at right angle to the dip direction. Strike is formed by the intersection of dip direction and imaginary line that run along the horizontal surface.
Figure 2. Strike and dip directions are shown.
So strike slip faults are called transform faults their movement is along strike and pass one another.
Figure 3. On the lower left is reverse fault and to the right is strike slip or transform fault.
Dip-slip faults includes normal and reverse fault. Once again had to acknowledge that normal faults are those which moves according to the gravity action and reverse faults are those which moves anti-gravity. These faults are the reason for the earthquakes. When movement of the two Earth crust block trigger it rubs against each other and as their are solid rocks, they are rough and keeps the crust intact so their movement triggers earthquake.
Folds
Folds are the structures that are formed due to plate movements. Faults are also responsible in its forming. These are the folded starta of the Earth's crust the fold are formed when originally horizontal strata as deposition is always horizontal it is curved or bent, deformation in the strata due to forces.
Figure 4. Component of fold.
Fold are basically the deformation and it occurs when forces on both sides, somewhere the forces have to be accommodated so the strata where it can bend, forms the fold. There are types of folds anticline and syncline. Anticline is shown in the figure 4 it is the convex upward fold. In it's inner part, lowest one will have the older rocks as it is the core and younger on the limbs and hinge. the syncline is the vice-versa. It will be concave upward and in the core the inner portion will have the younger rocks the limbs will have older rocks.
Geology is the study of the Earth, the materials of which it is made, the structure of those materials, and the processes acting upon them. It includes the study of organisms that have inhabited our planet. An important part of geology is the study of how Earth's materials, structures, processes and organisms have changed over time.
What Does a Geologist Do?
Geologists work to comprehend the historical backdrop of our planet. The better they can comprehend Earth's history, the better they can predict how occasions and procedures of the past might impact what's to come. Here are a few illustrations:
Volcanic Hazards Map: Geologists prepared this volcanic hazards map to communicate the location of hazardous areas to citizens, government agencies, and businesses. To prepare a map like this requires an understanding of volcanoes, an ability to recognise volcanic deposits in the field, an ability to prepare a map, and an ability to communicate. All geological tasks require a diversity of skills. This is why students who are interested in geology are encouraged to do well in all of their courses and to seek advanced training in Earth science, chemistry, physics, math, computers, and communication skills.
Geologists study Earth processes
Many procedures, for example, avalanches, tremors, surges, and volcanic emissions can be perilous to individuals. Geologists work to comprehend these procedures all around well enough to abstain from building essential structures where they may be harmed. On the off chance that geologists can plan maps of territories that have overflowed before, they can get ready maps of ranges that may be overwhelmed later on. These maps can be utilised to direct the improvement of groups and figure out where surge assurance or surge protection is required.
Geologists study Earth materials
Individuals utilise Earth materials consistently. They utilise oil that is created from wells, metals that are delivered from mines, and water that has been drawn from streams or from underground. Geologists lead concentrates that find shakes that contain imperative metals, arrange the mines that deliver them and the techniques used to expel the metals from the stones. They do comparable work to find and deliver oil, common gas, and groundwater.
Geologists study Earth history
Today we are worried about environmental change. Numerous geologists are attempting to find out about the past atmospheres of Earth and how they have changed crosswise over time. This authentic geography news data is important to see how our present atmosphere is changing and what the outcomes may be.
Geology as a Career
Geology can be an extremely intriguing and remunerating vocation. The base preparing required is a four-year higher education in geography. Pre-understudies who are keen on getting to be geologists ought to take a full educational programs of school preliminary courses, particularly those in math, science, and composing. Courses identified with PCs, topography and correspondence are likewise significant.
Geologists work in an assortment of settings. These include: normal asset organisations, natural counselling organisations, government offices, non-benefit associations, and colleges. Numerous geologists do handle work at any rate part of the time. Others invest their energy in research facilities, classrooms or workplaces. All geologists plan reports, do computations and utilise PCs.
In spite of the fact that a four year certification is required for passage level business, numerous geologists procure ace's and additionally doctorate degrees. The propelled degrees give a more elevated amount of preparing, regularly in a geography claim to fame territory, for example, fossil science, mineralogy, hydrology, or volcanology. Propelled degrees will frequently qualify the geologist for supervisory positions, inquire about assignments, or showing positions at the college level. These are probably the most looked for after employments in the field of geography.
Work open doors for geologists are great. Most topography graduates with a solid scholarly foundation and decent evaluations experience no difficulty discovering business on the off chance that they will move to an area where work is accessible.
Employment Outlook
Throughout the following quite a long while, the quantity of geography employment opportunities is relied upon to surpass the quantity of understudies moving on from college topography programs. Beginning pay rates for geologists have as of late extended from $50,000 to $100,000 every year.
How Can You Become a Geologist?
On the off chance that you are a pre-undergrad, you can get ready to wind up distinctly a geologist by doing admirably in the greater part of your courses. Science courses are particularly essential, however math, composition, and different controls are utilised by each geologist amid each working day.
In the event that you are thinking about school or doctoral level college, there are numerous colleges that offer courses or projects in geography. Visit the site of a school that offers a topography degree, connect with the geography office, let them know you are intrigued and make game plans to visit the grounds. Try not to be reluctant. Great schools and teachers need to be reached by intrigued understudies.
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