Geomorphology 07 _ Daily Class Notes PDF
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This document contains lecture notes on plate tectonics, covering topics such as continental plates, oceanic plates and the formation of mid-ocean ridges. The notes include details about types of plate margins and factors like magma and tectonic forces involved.
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Geography Ch 01: Geomorphology Lecture 07: Plate Tectonics (Part 03) Plate: A plate is a geological structure approximately 100 km deep...
Geography Ch 01: Geomorphology Lecture 07: Plate Tectonics (Part 03) Plate: A plate is a geological structure approximately 100 km deep,constituting the uppermost part of the Earth. It comprises both the crust and the upper part of the upper mantle, collectively known as thelithosphericplate. These plates are broken,interlockedfragmentsthatfloat over the asthenosphere. They are in constant motion, not stationary, and the study of this movement is known as tectonics study. Types of Plates: Continental Plate:A continental plate is a type oflithospheric plate that lies beneath a landmass. In reality, there isno completely land-based continental plate. For example, the EurasianPlate has the largest landmass, but italso contains some waterbodies.It is approximately 100 km deep. The continental crust is primarily composed of granite rocks. Oceanic Plate:An oceanic plate is a type of lithosphericplate thatlies beneath the ocean or sea.The oceanic crust is primarily composed of basaltic rocks. Continental-Oceanic plate:A continental-oceanic plateis a type of lithospheric plate that includes bothland and ocean areas. The part beneath theland consistsof granite rocks,while thepart beneath the oceanis composed of basaltic rocks.Most plates areapproximately100 km deep.Examples include the Indo-Australian Plate, North American Plate, South American Plate, Antarctic Plate, and Eurasian Plate. The Pacific Plate is the largest plate. There are 7 Major lithospheric Plates and Approximately 20 Minor Plates: PW Web/App:https://smart.link/7wwosivoicgd4 Major Plates: ○ Eurasian plate (Continental plate), ○ Pacific plate (oceanic plate) ○ African plate ○ Indo Australian plate ○ North American plate ○ South American plate ○ Antarctica plate Minor plates: ○ Philippine Plate ○ Burma plate ○ Caribbean plate ○ Nazca plate ○ Juan de Fuca's plate ○ Cocos plate ○ Arabian plate ○ Anatolian Plate ○ Java Plate Types of Plate Margins: DestructivePlateMargins:Destructiveplatemarginsareregionswheretectonic plates are destroyed. This occurs at convergent boundaries, where two plates collide,leadingtooneplatebeingforcedbeneaththeotherinaprocessknown as subduction. ConstructivePlateMargins:Constructiveplatemarginsareregionswhere new plates are formed. These margins are typically found in areas of divergence,wheretectonicplatesaremovingapartandmagmarisesfrom the mantle to create new oceanic crust. Conservative Margins: Conservative margins are regions where tectonic plates neither diverge nor converge. Instead,theplatesslidepasteachotheralongthesemarginswithout creatingnewcrustordestroyingexistingcrust.Thistypeofboundary is known as a transform fault boundary. Conservative margins are associated with intense earthquakes, which can be disastrous, PW Web/App:https://smart.link/7wwosivoicgd4 leading to significant loss of life and damage to infrastructure.Example: San AndreasFault. Constructive Plate Margins or Divergent Plate Boundaries: Constructive plate margins, also known as divergent plate boundaries, arecharacterizedbytheformationof mid-ocean ridges. The stages associated with the development of mid-ocean ridges include: ○ Intra-continental Rifting: Intra-continental rifting beginswhenhot,lessdensemagmarisesfromthemantle,creatingarising limb of the convection cell. As this rising magma reaches the Earth's crust, it causes the crust to crack and results in domal uplift. An example of this process is the Ethiopian Highlands, which exhibit features of domal uplift. As the magma continues to interact withthecrust,itexertstensileforcesthatpullthecontinents apart. This divergence causes the central portion to subside, creating a rift valley. The process of formingthisriftvalleyisknownasfaulting.Anexampleofariftvalleyformedthroughthisprocessis the Great African Rift Valley, which stretches fromMalawitotheDeadSeaalongtheIsrael-Jordan border. ○ Interplate Thinning: During the subsidence of the crust, the two parts of the crust move apartduetodivergentforces. Continued divergence causesfurthersubsidenceofthecontinental block. As the block reaches greater depths, it interacts more extensively with the magma, leading to additional melting. This process makes the plate increasingly thin. With the increased depth, water from neighboring seas or oceans can penetrate the area,resultingintheformationofanewnarrowlinearsea, such astheRedSea.Before20millionyearsago,theRedSeawaspart of a rift valley system. The Arabian Plateisriftingawayfromthe African Plate along an active divergent ridge system, forming the RedSea.Inthefuture,theGreat African Rift Valley may evolve into a long, narrow sea. ○ Formation of Oceanic Ridges: As thecontinentalblockbecomesincreasinglythin,magma canmoreeasilyintrudeandemergeaslava.Thisprocessleads totheformationofanoceanicridgeinthecenterofthesea. The process continues, expanding the sea floor and creating new ridges. For example, when South America and Africa PW Web/App:https://smart.link/7wwosivoicgd4 drifted apart, the AtlanticOceanwasformedwiththeMid-AtlanticRidgeemerginginthemiddle. The lava that forms the Mid-Atlantic Ridge isbasaltic in nature. At divergent boundaries, the lava that erupts is typicallybasaltic in composition. 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