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INTERNAL ENERGY

INTERNAL ENERGY . WHY ARE ROCKS FORMED?. The deformation of rocks. The movements of the Earth’s plates generates forces or STRESSES on the rocks of the lithosphere which cause deformations or changes in these rocks .

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INTERNAL ENERGY

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  1. INTERNAL ENERGY WHY ARE ROCKS FORMED?

  2. Thedeformation of rocks • Themovements of theEarth’splatesgeneratesforcesor STRESSES ontherocks of thelithospherewhich cause deformationsorchanges in theserocks. • Compressionalstess: comes fromopposingconvergentforces. (squeeze) • Tensionalor extensional: comes fromopposing and divergentformces. (stretch) • Shear stress: fromparallelforces, convergent and divergent. (tear)

  3. DEFORMATIONS

  4. Faults • Faults are fractures in therocks of theEarth’scrustwhere blocks havebeen displaced. (Tectonicforces are greaterthanresitstance). • Types: • Dip-slip faults: movementis vertical: Normal, reverse and vertical • Strike-slip faults: movementis horizontal: Sinistraltear and dextraltearfault.

  5. Faults Normal fault Reverse

  6. Strike slip faults

  7. Folds Folds are createdwhenrocksdeformbuttheydon’t break.

  8. Foldclass

  9. External geological processes • CausedbySolar Energy • Weathering • Erosion • Transportation • Sedimentation • Diagenesis

  10. Internal geological processes • Those come fromtheinternalheat and pressureinsidetheEarth. • Magmatism and tectonicplates: Theinternalheatcreates magma and produces volcanoes, geysers and thermalsprings. • Geothermalgradient: 30ºC/Km (average) • Highpressuresrisethemeltingpoint and keepthe rock solid.

  11. Melting…. • Melting can beproduced in places duetosomemechanisms: • A rise in temperatureprodecedbyfriction • A drop in pressure reduces themeltingpoint • Thepresence of liquids reduces themeltingpoint Magma fromdeepmantleisreleased at mid-oceanridges, rifts and hotspots.This magma isrich in iron and magnesiumand has a low fluid content.The magma fromthesubductionzone comes fromthemoltencrust and isrich in silicon, alumninium and gases.

  12. Internal geological processes • Metamorphism and tectonic place: • Itis a processwherethetypeordistribution of minerals in rockschangesbecauseifhighpressureorveryhightempreratures. Itiscalledisochemicalbecausethecomposition of the rock remainsunchanged. • Metamorphism can sometimesoccur in faultsor at thesites of meteorimpact.Itisalsofound in areaswithconvergentplateboundaries, such as subduction and continental collisionzones. • Metamorphicbelts: nexttothetrench and in thevolcanicarc.

  13. Types of metamorphism • Contactorthermal: producedbyanincrease of Tº. • Regional ordynamothermal: producedbyanincrease of Tº and Pº. • Dynamicmetamorphism: producedbyanincrease in Pº.

  14. Formation of mountainranges • AccordingtoTectonicPlatesTheorythere are twotypes of orogens: Orogensassociatedwithsubductionzonesand orogensassociatedwithcontinental collisions.

  15. Orogens: continental colission and subduction

  16. More orogens…

  17. Accretionorogens

  18. Accretionorogens • Thecollision of terranes(fragments of crustsurroundedbyfaults) isproducedwhensmallridges in theoceanicplatesreachthetrench. Butheresubductiondoesn’t stop. As a consequence, anaccretionorogenisformedontheedge of thecontinent as successivefragements are added.

  19. Isostasy • Isostasyisthestate of equilibriumbetweenthelithosphere and theplasticmantle: iftheweight of thelithosphereincreasesitusuallysinksintothemantle; ifitsweightdecreases, thelithospherenormallyrises.

  20. Isostasy • Isostasyassociatedwithglaciation: theweight of an ice cap causes part of thelithospheretosink. Whenthe ice melts, thelithosphererises and recoversitsinitialequilibrium. • Isostasyrelatedwitnerosion and deposition: thebottom of a basintendstosinkwhen a thicklayerisdeposited (subsidence). Whenitiseroded, theoppositprocessoccurs.

  21. Risksassociatedwith geological activity Seismicrisk Volcanicrisk

  22. Types of eruptions

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