Geology: A Comprehensive Guide to Earth’s Processes and Structures

Posted on May 4, 2024 in Geology

Orogeny: The Process by Which Mountains Originate

Andean-Type Orogeny:

• Located at margins where oceanic lithosphere subducts beneath the sediment-laden continental lithosphere.
• The oceanic plate creates an accretionary prism.
• The heat generated by friction between the plates, along with the presence of water in the subducting oceanic lithosphere, causes partial fusion.
• This results in volcanic eruptions, and the magma rises due to its lower density.
• The excess magma remains inside the crust, solidifies, and contributes to the thickening of the subduction plate.

Island Arc Orogeny:

• Located at margins where the subducting oceanic lithosphere spontaneously subducts beneath another oceanic lithosphere.
• The trench is very deep, and intense volcanic activity creates the island arc.

Alpine Orogeny:

• Originates at continental convergence sites.
• As the subducting continent closes the ocean basin, the collision causes the crust to thicken and ride up over another continent.

Deformation Rates

Elastic:

• The material will be subjected to deformation under effort but will recover its shape and volume once the effort stops.

Plastic:

• The deformation remains even after the effort has ceased.

For Rupture:

• This is where stress causes loss of internal cohesion of the material and fracture.
• There is a limit of plasticity for each material.

Factors Influencing Deformation

• Temperature
• Lithostatic pressure
• The presence of water or other fluids

Folds

• Flexures in which the masses of rock imply a plastic behavior of rocks that have been subjected to efforts.
• The folds vary according to their direction and dip.

Types of Folds:

• Anticline: The core contains older materials.
• Syncline: The core contains younger materials.

Jointing

• Fractures in which blocks do not move with respect to each other, or if they do, it is to widen the fracture.

Faults

• Fractures in which one block is displaced with respect to another.

Normal or Direct Fault:

• The fault plane dips toward the sunken lip.
• It arises in response to tension.

Reverse Fault:

• The fault plane dips toward the raised lip.
• It arises in response to compressional forces.

Tear Fault:

• Block displacement is horizontal.

Horst:

• The block lifted on both sides of the fault.

Rift:

• The downthrown block is limited on both sides of the fault.

Minerals

• Silicon and oxygen are the most common elements in minerals.

Crystals

• Have a perfectly ordered structure in which their atoms form networks.
• Are minerals with geometric shapes.
• Are formed by the solidification of molten materials, sublimation of dissolved substances in gases, or chemical precipitation from an aqueous solution.

Metamorphism

• Changes experienced by rocks in their composition or texture due to the action of temperature, pressure, or chemically active fluids.
• Tends to occur in solid-state conditions.

Types of Metamorphism:

Isochemical:

• The chemical composition of the rock does not change.

Metasomatic:

• The chemical composition of the rock changes due to the presence of chemically active fluids.

Dynamic:

• Occurs due to changes in pressure.

Contact:

• Produced by an increase in temperature due to igneous intrusion.

Regional:

• Produced by the simultaneous increase of pressure and temperature.

Magma

• Molten silicate that contains water vapor and other gases.
• Usually has a solid fraction consisting of minerals that have not yet crystallized.
• Its origin is due to an increase in temperature caused by friction between plates, decompression, or the incorporation of water, which lowers the melting point.

Types of Magmas:

Basalt:

• Arises from the partial melting of mantle peridotite.
• Characteristic of oceanic ridges.

Andesitic:

• Originates from the partial melting of subducting oceanic crust.
• Produced by the friction of the plates and the presence of water.

Granite:

• Originates in subduction zones from the fusion of materials from the lower continental crust.

Igneous Rocks

• Depend on the form, size, and velocity at which the magma cools.

Plutonic Rocks:

• Originate in the deep Earth, where the magma cools slowly, allowing for well-crystallized minerals.

Granite:

• Gray or pink in color.
• Fundamental constituents: quartz, potassium feldspar, and mica.

Syenite:

• Pink in color.
• Major component: plagioclase feldspar.
• Differs from granite in that it does not contain quartz.

Diorite:

• Gray in color.
• Constituents: feldspar, biotite, and amphibole.

Gabbro:

• Dark rock.
• Constituents: pyroxene, plagioclase, and biotite.
• May contain olivines.

Peridotite:

• Very dark rock.
• Constituents: pyroxene and olivine.
• Most abundant rock on the planet.

Volcanic Rocks:

Located in the magma q lies on the surface is very fast cooling crystallize poorly. ** Basalt: It extends through all the ocean floor is very dark color usually has a parent microcistalina **Andesitic: Color Gray is similar to the diorite. ** Rhyolite: Light color similar to granite ** Tranquitas: composision light color and is similar to the syenite .** Obsidian: glassy texture is black, its highly variable composision ** Pumice: Light color, low density .** volcanic gap: Frome by thick volcanic rocks framentos united by Toba ash **: It is caused by union of pyroclasts due to high temperatures with q was expelled from the volcano .*** filonianas Rocks: The magma does not reach the surface but it is near** Aplite: Roca holocristalina textured, fine-grained homometrica, its color is gray, his composision is similar to granite: ** Porphyry granite rock of very large crystals holocristalina .** Diabase: A large rock crystal holocristalia and slender, green is .*** Continental Division: ** thermal model: The magma rises and raises the temperature of the lithosphere and the arches. After fracture, the separation of the edges form the continental and oceanic itosfera depues extention will be made .** oceanic tectonic model: The lithosphere is stretched, this stretching causes the thinning and would break after the sepraracion of continental lithosphere extension would make the *** oceanica Wilson Cycle: The heat under the supercontinent q rise makes this particular places and the lithosphere becomes thinner and fragments It creates a rifty give rise to an ocean inteior. The fragmentation and reunification of contienentes would be the main phases of the Wilson cycle *-*-*-*-*-*-* *** weathering Physics: Consists of the division or disintegration of rocks into fragments without q ‘ alteration of their chemical composition or Mineralogica ** Gelifraccion: The breaking of rocks produced x ice. Xq occurs by passing the liquid water to ice volume increases .** Haloclastia: The breaking of rocks produced x the growth of salt crystals. If water from the rock has dissolved salts on evaporation forms crystals in the pores of the rocks promoting their disaggregation** Expansiojn Thermal: Temperature changes dilate or contract breaching the rocks may .*-* Decompression: The removal or separation of lanjaron q occur in the rocks to support the charge q free *** Chemistry: The alteration of chemical composition and mineralogy of the rock produced x water, air, living ** Hydrolysis: The results from the dissolution of water in H + ions and OH are very reactive and decompose many minerals ** Oxidation : Eb presence or lose electrons and are oxidized ** Carbonation: Produced by carbonic acid. It is this acid-laden water dissolves the limestone or Dissolution ** *** It is the result of weathering is a set of surfaces altered and dissolved q fragments transferred to places usually lowest (transport agents: water, wind, ice and gravity) ** Surface water: q The materials tranport a river is called load. The load can be Trasnportes in solution, if soluble substances supension if material is small in size and in the larger background .** Glaciers: Ice as an agent of erosion and trasponte. Glaciers transport the meterial fall from the slopes q q the glacier erodes its own cause .*-* Wind: The intervention is limited to areas without vegetation and with an abundance of loose material. The fine-sized materials are transported in suspension while those of medium size q by saltation * * Gravity processes: These are movements of materials to lower parts produced by the direct action of gravity .*** diagenesis:Set of processes q x the sediment becomes sedimentary rock. During this may alter the chemical or compisicion rock ** mieneralogia of compaction is to reduce the volume of a rock. THEREFORE occurs as q on a layer of sediment deposited new material q exert pressure on the former. The volume of the rock and thus diminish the pores and disminiyen q water may have ** Cementing: The q presipitacion minerals are dissolved in water, mineral presipidado acts of cement between the grains of sediment fills the porosity huecosreduciendo the rock (limestone and silica) *** dendritic Rocks: Sedimentary rocks are hn dendritic formed from fragments of other rocks have been tranportes q in edo solid as a function of size are the differences: ** Rudite: These are rocks with coarse grains. These grains may be fragments of any rock (clasts). If the clasts are angular and are called gap if they are rounded .*-* pudinfa Arenitas: They are of medium size grains including both the media without diagenizar sediments are formed from sandstone .** shales, are of fine size are the most abundant are divided into groups: Siltstone: Diagenesis of silts and clays argillites .*** diagenesis of carbonate rocks, are formed of calcium carbonate and magnesium by Cotiuida ** Limestone CaCO ₃may have a chemical origin, the carbo. . dissolved in water q presipita without involving bodies. Other home presipitacion biochemistry and the agencies have intervened. Or sometimes in the rock itself has accumulated remains of organisms **Dolomite: This CONSTITUTE by CaCO ₃and Mg .*-* Margas: These are rocks composed of shale and limestone rocks evaporites **: These rocks formed x presipitacion of mineral salts dissolved in water q have had an intense evaporation. They form in arid areas and inland seas with strong evaporation (halite, gypsum, silvina) *** Rocks Siliceo-alimuo-Ferrugio: They arise by alteration of soils in tropical cliams ** dialomita is formed by accumulation of debris diatimeas *** Rocks organogenic: They originate by accumulation of organic remains after q q have been altered by other agencies. Sized soft tissue is preserved in its formation and living beings have been disingenuous, have provided raw material or alteredNatural Coals .**: They are formed from plant debris accumulated in swamps, lagoons and deltas. These environments poor in bacterial action or perform a partial decomposition of plant material q results in a relative enrichment in carbon (peat, coal) ** oil was formed from the remains of plankton accumulated in the seabed. It is proved necessary to cover the deposits would get organic silt and clay for q not rust in this environment fermentacuin processes remove the O and N in the rest of enriching organic C and H and so does a mixture of hydrocarbons’. Petroleum source rock, q is in the oil and originates in it are occupying pores and voids