1_earth_system.ppt

By Dr. Muhammad Edisar, MT

*FI-6121 System Fisis Bumi Lecturer: Dr.M.Edisar, MTThe Composition of the Earth



*(Adapted from, Beatty, 1990.)



* W.J. Kious and R.I. Tilling, This Dynamic Earth: The Story of Plate Tectonics, U.S. Geological Survey, 1996. By Dr. Muhammad Edisar, MT


*Komposisi Bumi Bedasarkan:

Komposisi KimiaUnsur-unsur utama

Sifat Fisis By Dr. Muhammad Edisar, MT By Dr. Muhammad Edisar, MT



*Komposisi Kimia Inti BumiZona Pusat Bumi Mulai pada kedalaman ~ 2,900 kmDisususun dari Fe-alloysInti bagian luar Cair Fe, Ni, SInti bagian luarPadat (akibat tekanan yang sangat besar)Fe



*Batas Inti mantle (CMB) didefinisikan oleh diskontinuitas GutenbergZone dari 200 - 300 km, ditandai D11



*Mantle

Daerah sekitar inti ~ 83 % dari volume Bumi < kerapatannya dari intiSeluruh mantle disusun dari dua silikat Fe dan MgOlivine (Mg, Fe)2SiO4Pyroxene (Mg, Fe)SiO3



*Mineral ini berubah bentuknya pada tekanan yang berbeda.Akibatnya ada batas dalam mantle yang menggambarkan perubahan fasa, atau ikatan atom dari mineral tersebut.Dua perubahan fase yang paling penting terjadi pada kedalaman 410-km, dan 660-km.



*Pada mantle bagian atas (diatas 660-km) olivine and pyroxene ditemukan sebagau peridotite Pada mantle bagian bawah (dibawah 660-km) olivine and pyroxene berbentuk perovskites dan jauh lebih sedikit jumlahnya dari oxide, magnesiowstite



*Batas 660-km adalah penting untuk beberapa alasan:Menggambarkan gempa bumi paling dalam Perubahan fase mineral pada kedalam ini dapat di buat di laboratorium, temperature pada kealaman harus ~ 1700C



*

Kerak (Crust)

Batas Mantle Kerak dibangun oleh diskontinuitas Mohorovii Daerah ketebalannya dari 10 - 70 kmTerdiri dari dua jenis 1. Samudra 2. Benua



*Kerak Samudra Kerak tipis dibawah lautan BasaltKetebalan rata-rata sekitar 8 km~ 2-km Basalt bantal ~ 6-km GabbroDensitasnya 3.2 g/cm3Kompoisisi kaya akan Ca, Mg, Fe< 50 % SiO2



*Kerak BenuaKetebalannya dari 30 - 70 km Paling tipis dimana lempeng benua bergerak menjauh dan terpisah Paling tebal ada dibawah pegunungan Densitasnya rata-rata 2.7 g/cm3GranitKomposisinya kaya akan Si, Al, Na, K> 50% SiO2


DEPARTMENT OF PHYSICS

Komputasi Fisika

* By Dr. Muhammad Edisar, MTSifat Fisis



*lithosphereKulit bagian luar dari Bumi yang Kaku (rigid)Disusun dari :Mantel Bagian AtasKerak SamudraKerak Benua Ketebalannya 70 - 125 km



*asthenosphereDaerah kulit bagian luar Bumi yang terletak dibawah lithosphereMeluas sampai kedalaman ~ 220-kmBersifat plastis



Komputasi Fisika

* By Dr. Muhammad Edisar, MTTeori Tektonik Lempeng Sintesa Modern



*Permukaan Bumi terbagi ke pada 12 plat utama Plate bergerak secara horizontal terhadap satu sama lainPlate mengapung ataumeluncur diatas lapisan asthenosphere viskositas tinggi.



*

Lempeng terdiri dari kerak samudra dan kerak benua

Aksi utama tektonik lempeng terjadi pada pinggiran lempeng



*

Dalam skala waktu manusia batas-batas ini ditandai dengan adanya gunung api dan kejadian-kejadian gempabumi. Diatas studi waktu geologi tas-batas btersebut adalah tempat-tempat terjadinya splitting, shifting dan crumpling dari benua



*Volcanoes of the World (Smithsonian Institution Global Volcanism Program)



*



Komputasi Fisika

* By Dr. Muhammad Edisar, MTJenis-jenis pergerakan lempeng


*Lempeng Divergent Batas penyebaran (Spreading)Daerah healed kerak atau fissuresContoh :Rift Valley dari Afrika bagian timur Mid-Atlantic ridgeGunung api, gempabumi By Dr. Muhammad Edisar, MT



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*Heezen and Tharp



*Lempeng Convergent Pada batas lempeng convergent respons terhadap tumbukan lempeng akan bervariasi dengan jenis kerak yang bersangkutan Ada tiga kemungkinan kombinasi:



*Kerak samudra converging with kerak samudra:Subduksi satu lempengFormasi dari sebuah busur kepulauan Gunung apiGempabumi Contoh kepulauan Japanese



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*Kerak samudra converging degan kerak benua :Formasi dari rantai pegunungan Gunung apiGempa bumiContoh Pegunungan Andes



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*Kerak benua converging dengan kerak benua :Overriding dari satu lempengFormasi dari daerah pegunungan Gempa bumiContoh Himalayas



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*Transform Boundariesside-slip boundary create fault zonesearthquakesexample San Andreas



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*Cross section by Jos F. Vigil from This Dynamic Planet



*50 million years



*150 million years



*250 million years



*EcosphereThat part of the earth consisting of the atmosphere, hydrosphere, lithosphere, and biosphere



*AtmosphereThe gaseous layer which surrounds the earth, and which is held by gravitational attraction. It consists of layers, the bottom ones of which are:Thermosphere > 80 kmMesopauseMesosphere45 - 80 kmStratopauseStratosphere 12 - 45 km TropopauseTroposphere 0 -12 km



*HydrosphereEarth's water, in any physical state Gaseous LiquidSolid



*LithosphereThe outermost part of the solid earth, consisting of the entire crust and the upper mantle, from the surface to a depth of about 70 kilometers (km)It is stronger and mechanically more rigid than the asthenosphere (70 - 250 km), which lies under it



*Interior of the EarthCrust Continental (0-40 km, to a maximum of 100km) Oceanic (0-10 km)Mantle Upper (bottom of crust to 700 km, and includes the transition zone (350 to 700 km) Lower (700 - 2900 km)Core Outer (2900 - 4980 km - liquid iron-nickel)Inner (4980 - 6370 km - solid)



*BiosphereInterface layer between earth's crust, atmosphere, and hydrosphere where life is foundIncludes the total ecosystem of the earth



*EcosystemCommunity of interacting organisms, of all speciesIncludes interactions of this community with the chemical and physical systems of earth



*Human ActivitiesInteract with the natural world, causing changes in the ecosystemChanges vary in magnitude and temporal scale



*Environmental IssuesChanges in the ecosphere caused by:Natural processesHuman activitiesOften cause changeAffect the rate at which change occursOr both



*Changes By Other SpeciesHumans are not the only species to cause environmental change Cyanobacteria, the first organisms capable of photosynthesis, gradually changed the atmosphere of earth from one without oxygen to one with the present 21% oxygen content



*So What Makes Humans Different?Humans are the first species to be aware of their influenceHumans assume, to some extent, responsibility for wise management of the planet



*Technology ImprovementsDuring the last fifty years Have greatly contributed to our awareness of environmental changeEspecially contributing to our knowledge of global scale processesGreatly enhanced out knowledge of the temporal scale of global change



*Examples of Technological ChangeSatellite observationsComputational powerRapid communication (Internet)



*Changes to the EcosphereMany examples of modification of ecospheric components have been describedRepresentative examples of these modifications are shown on the following slides



*Atmospheric ModificationsDepletion of ozone (O3) in the ozone layer (stratosphere) which affects UV light absorptionOzone holeLeads to increased rates of skin cancerAcid deposition introduction of pollutant gasses into the atmosphere leads to the formation of acid rain



*Atmospheric Modifications cont.Modification of the climate system by the introduction of greenhouse gasesMajor gases are carbon dioxide, freons, methaneWill lead to a warmer earth, and probably increase number and severity of major stormsMay affect short and medium term climate, and may modify the areas in which food can be grown



*Hydrological ModificationsDiagram shows a local example of the hydrological cycle



*Hydrological Cycle Modifications Withdrawal of waterPollution of waterImpoundment of water (dams) Modifications in erosion and depositional rates Silting of rivers and estuariesIncreased erosion below dams



*Biosphere ModificationsMobilization and redistribution of chemical elements Most important carbon (C), nitrogen (N), and oxygen (O)Results in enrichment and depletion of various parts of the system, leading to problems like red tide, depletion of soil productivty, etc.



*Biosphere Modifications cont.Human activities change natural environmentOften results in changes if species distribution, especially in loss of biological diversity (biodiversity)Rapid expansion of urban and suburban areas decreases available habitatDeforestationExpansion of farming into marginal environmentsLand use that is insensitive to long term changesSalinization



*Results of Environmental ChangeSpecies reductionMass mortality - a large number of individuals die, which may lead to a new equilibrium distribution, with a smaller number of individuals of the species in question, or the original equilibrium may be approximately restored, to precatastrophe levels Extinction - A complete elimination of a species. Extinction can and does occur naturally - Man's activities have increased the rate of extinction



*Natural EventsNatural events often lead to mass mortality in many species - extinction may occur in severely geographically restricted speciesExamples:EarthquakesVolcanoesHurricanes Small meteorite impacts



*OverviewGeologic TimeMovements of the ContinentsEarth MaterialsTectonic ForcesWeathering and Erosion ProcessesErosional Agents and Deposition



*Geologic TimePretend the age of the earth (4.6+ billion years) is compressed into one calendar year.January 1 - Earth and planets formedEarly March - liquid water stands in pools.Late March - earliest lifeJuly - oxygen is important part of atmosphereOctober 25 - multicellular organismsLate November - plants and animals abundantDecember 15 to 25 - dinosaurs arise and disappear11:20 pm, December 31 - Humans appearOne second before midnight - Automobile invented



*Formation of the Earths Interior@5 bya, plantesimals (meterorites,icy comets) collide heat released (Kinetic energy to thermal energy)Entire planet melts (still cooling today)Gravity sorts materials by densityFe in centerSi and O compounds towards surface



*The Upper Mantle and CrustCrust (5 mi for ocean, 25 mi for continents)Dense iron-rich basalts (mafic) make up ocean floor Fe, Silica, magnesiumSilica- rich rock makes up the continents (felsic) Silica, aluminum



*General trends: temperature, density Horizon composition, behavior

The Earths InteriorDistance: 6730 km (3963 miles)



*What is tectonics?From Greek tektonikus meaning building or constructionPlate tectonics refers to the process of plate formation, movement, and destruction.



*What is a Plate?Lithospheric plate: crust + upper mantleAesthenosphere: plastic mantle



*History of Plate TectonicsFit of coastlines recognized earlySir Francis Bacon (1600s)No mechanism for motion



*1915 Alfred Wegener proposes theory of continental drift.

Supercontinent Pangaea (all-earth) [225mya].Fragmentation and drift to current positions.



*Plate Movement History



*Wegners evidenceFit of continentsFossil plants, animals, rock types / geology match on opposite shoresdeposits inconsistent with current geography



*Striking Match of Biological Regions



*Striking Match of Geologic Regions



*History of Plate TectonicsProblem with continental drift?No sound mechanism for the drift!Wegner hypothesizes spin of earth or tides..



*History of Plate TectonicsNew theory for motion: Arthur Holmes (1930s)thermal convective cells in the upper mantle (aesthenosphere) theory is largely ignored



*History of Plate TectonicsIn the 1960s, Harry Hess and Robert Deitz (geophysicists) propose sea floor spreading along mid-oceanic ridges for plate motion.



*Sea Floor Spreading



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*Plate Tectonics TheoryContinental Drift + Sea Floor Spreading + new data Theory of Plate Tectonics



*Plate Tectonics TheoryPlate boundaries: main location for Earths volcanic and earthquake activity. This is main place where mountains are created.Type of plate boundary determines activity.3 typesdiverging (spreading)converging (colliding)transform (sliding past each other)



*Crustal ProcessesDestruction (subduction)Creation (volcanism )Alteration / deformation (folding and faulting)



*Geography of the Plates7 major plates; several minor platesSmall plates / boundaries still unknown



*Plate Margins: how do we know?Marked by volcanic and tectonic activity



*Divergent Plate BoundariesLandscape features: land: rift valleys, volcanic mountains, thinning crustocean/sea: rift valleys, mountain ranges



*Divergent Plate BoundariesExamples:Atlantic Mid-Oceanic RidgeRed SeaRift valleys of eastern Africa



*Convergent Plate BoundariesActivity: subduction; shallow to deep earthquakes; volcanism (continental)Features: ocean trench; explosive volcanic mtns on continental margin



*Earth MaterialsThree major rock typesIgneousSedimentaryMetamorphic



*Igneous RocksIgneous (ignus = fire)Formed from the cooling of molten rock (magma/lava), a process called crystallization.Slow cooling larger crystals > dense rockRapid cooling small crystals > lighter rock



*Two classes of igneous rocksintrusive: formed inside the Earthextrusive: formed at Earths surface



*Igneous Intrusive RocksCools slowly (thousands of years)Visible crystalsExamples - granite- diorite- gabbro



*Igneous Extrusive RocksCools rapidly - exposed to surfaceNo visible crystalsExamples - rhyolite - andesite -basalt



*Some unique rock types Pumice (vesicular)- sometimes so light it floats!Obsidian glassy, curved fracturingused for arrowheads by Native Americans



*Typical Igneous IntrusionsKnow: Batholith and Dike



* Exposed Batholiths

Sierra Nevada, CA



*Sills and Dikes

Dike: Grand Canyon, AZGranite sill in schistDike: Coast Ranges, BC



*Sills and Dikes



*Igneous Extrusive LandscapesVolcanic neck and dike: Shiprock, NMVolcanic cones, obsidian flow: Mono Craters, CA



*Sedimentary Rocks



*CompactionCementingSedimentary RocksFormationRelative Abundance by Type



*Sandstone (larger grains)Shale (fine grains)Limestone (CaCO3)



*Where do Sedimentary Rocks Form?Terrestrial environments (non-marine) Rivers and floodplains (fluvial environment) Lakes Deserts (aeolian environment) Marine environments Continental shelf Continental slope and rise (deep sea fans) Abyssal plain Beach and barrier islands



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*Metamorphic Rocks or Thats very Gneiss, but I dont give a Schist!Gneiss (broad foliation)Schist (narrow foliation)



*Which Type?



*Which Type?Sedimentary - limestone and shale



*What type?



*What type?Metamorphic - Amitsoq Gneiss, Greenland, Oldest known rocks



*What type?



*What type?Sedimentary - Sandstone in Utah



*What type?



*What type?Extrusive Igneous - Reunion Island, S. Pacific



*What type?Morro Rock, CA



*What type?Intrusive IgneousMorro Rock, CADevils Tower, Wyoming



*The Rock Cycle


1_earth_system.ppt

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