FI-6121 System Fisis Bumi Lecturer: Dr.M.Edisar, MT

FI-6121 System Fisis Bumi Lecturer: Dr.M.Edisar, MT

The Composition of the Earth

© By Dr. Muhammad Edisar, MT

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(Adapted from, Beatty, 1990.) © By Dr. Muhammad Edisar, MT

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W.J. Kious and R.I. Tilling, This Dynamic Earth: The Story of Plate Tectonics, U.S. Geological Survey, 1996.

© By Dr. Edisar, Edisar, MT MT © Muhammad By Dr. Muhammad

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Komposisi Bumi Bedasarkan: 

Komposisi Kimia 



Unsur-unsur utama

Sifat Fisis


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Komposisi Kimia Inti Bumi  



Zona Pusat Bumi Mulai pada kedalaman ~ 2,900 km Disususun dari Fe-alloys 

Inti bagian luar 





Cair Fe, Ni, S

Inti bagian luar  

Padat (akibat tekanan yang sangat besar) Fe


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Batas Inti –mantle (CMB) didefinisikan oleh diskontinuitas Gutenberg Zone dari 200 - 300 km, ditandai D11


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Mantle    

Daerah sekitar inti ~ 83 % dari volume Bumi < kerapatannya dari inti Seluruh mantle disusun dari dua silikat Fe dan Mg  

Olivine (Mg, Fe)2SiO4 Pyroxene (Mg, Fe)SiO3 © By Dr. Muhammad Edisar, MT

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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.


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Pada mantle bagian atas (diatas 660km) 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, magnesiowüstite


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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 ~ 1700°C


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Kerak (Crust) 

 

Batas Mantle – Kerak dibangun oleh diskontinuitas Mohorovičić Daerah ketebalannya dari 10 - 70 km Terdiri dari dua jenis 1. Samudra 2. Benua


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Kerak Samudra

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 

Kerak tipis dibawah lautan Basalt Ketebalan rata-rata sekitar 8 km  

  

~ 2-km Basalt bantal ~ 6-km Gabbro

Densitasnya 3.2 g/cm3 Kompoisisi kaya akan Ca, Mg, Fe < 50 % SiO2 © By Dr. Muhammad Edisar, MT

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Kerak Benua 

Ketebalannya dari 30 - 70 km 





  

Paling tipis dimana lempeng benua bergerak menjauh dan terpisah Paling tebal ada dibawah pegunungan

Densitasnya rata-rata 2.7 g/cm3 Granit Komposisinya kaya akan Si, Al, Na, K > 50% SiO2 © By Dr. Muhammad Edisar, MT

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Sifat Fisis


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lithosphere 



Kulit bagian luar dari Bumi yang Kaku (rigid) Disusun dari :    

Mantel Bagian Atas Kerak Samudra Kerak Benua Ketebalannya 70 - 125 km


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asthenosphere 

 

Daerah kulit bagian luar Bumi yang terletak dibawah lithosphere Meluas sampai kedalaman ~ 220-km Bersifat plastis


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Teori Tektonik Lempeng Sintesa Modern


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Permukaan Bumi terbagi ke pada 12 plat utama Plate bergerak secara horizontal terhadap satu sama lain Plate “mengapung” atau“meluncur” diatas lapisan asthenosphere viskositas tinggi. © By Dr. Muhammad Edisar, MT

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Lempeng terdiri dari kerak samudra dan kerak benua

Aksi utama tektonik lempeng terjadi pada pinggiran lempeng


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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


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Volcanoes of the World (Smithsonian Institution Global Volcanism Program) © By Dr. Muhammad Edisar, MT

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Jenis-jenis pergerakan lempeng


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Lempeng Divergent   

Batas penyebaran (Spreading) Daerah healed “ kerak ” atau fissures Contoh :  



Rift Valley dari Afrika bagian timur Mid-Atlantic ridge

Gunung api, gempabumi


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Heezen and Tharp


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Lempeng Convergent 

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


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Kerak samudra converging with kerak samudra:   

 

Subduksi satu lempeng Formasi dari sebuah busur kepulauan Gunung api Gempabumi Contoh  kepulauan Japanese


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Kerak samudra converging degan kerak benua :   

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Formasi dari rantai pegunungan Gunung api Gempa bumi Contoh Pegunungan Andes


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Kerak benua converging dengan kerak benua :   

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Overriding dari satu lempeng Formasi dari daerah pegunungan Gempa bumi Contoh  Himalayas


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Transform Boundaries   

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“side-slip boundary” create fault zones earthquakes example  San Andreas


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Cross section by José F. Vigil from This Dynamic Planet © By Dr. Muhammad Edisar, MT

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50 million years


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150 million years


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250 million years


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Ecosphere 

That part of the earth consisting of the atmosphere, hydrosphere, lithosphere, and biosphere


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Atmosphere 

The gaseous layer which surrounds the earth, and which is held by gravitational attraction. It consists of layers, the bottom ones of which are:  

  

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Thermosphere > 80 km Mesopause Mesosphere 45 - 80 km Stratopause Stratosphere 12 - 45 km Tropopause Troposphere 0 -12 km © By Dr. Muhammad Edisar, MT

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Hydrosphere 

Earth's water, in any physical state – 

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Gaseous Liquid Solid


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Lithosphere 

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The 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


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Interior of the Earth 

Crust –  

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Mantle – 

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Continental (0-40 km, to a maximum of 100km) Oceanic (0-10 km)

Upper (bottom of crust to 700 km, and includes the transition zone (350 to 700 km) Lower (700 - 2900 km)

Core – 

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Outer (2900 - 4980 km - liquid iron-nickel) Inner (4980 - 6370 km - solid) © By Dr. Muhammad Edisar, MT

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Biosphere 

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Interface layer between earth's crust, atmosphere, and hydrosphere where life is found Includes the total ecosystem of the earth


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Ecosystem 

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Community of interacting organisms, of all species Includes interactions of this community with the chemical and physical systems of earth


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Human Activities 

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Interact with the natural world, causing changes in the ecosystem Changes vary in magnitude and temporal scale


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Environmental Issues 

Changes in the ecosphere caused by: 

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Natural processes Human activities   

Often cause change Affect the rate at which change occurs Or both


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Changes By Other Species 

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Humans 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


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So What Makes Humans Different? 

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Humans are the first species to be aware of their influence Humans assume, to some extent, responsibility for wise management of the planet


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Technology Improvements  

During the last fifty years Have greatly contributed to our awareness of environmental change 

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Especially contributing to our knowledge of global scale processes

Greatly enhanced out knowledge of the temporal scale of global change © By Dr. Muhammad Edisar, MT

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Examples of Technological Change   

Satellite observations Computational power Rapid communication (Internet)


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Changes to the Ecosphere 

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Many examples of modification of ecospheric components have been described Representative examples of these modifications are shown on the following slides


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Atmospheric Modifications 

Depletion of ozone (O3) in the ozone layer (stratosphere) which affects UV light absorption  

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Ozone “hole” Leads to increased rates of skin cancer

Acid deposition – introduction of pollutant gasses into the atmosphere leads to the formation of “acid rain” © By Dr. Muhammad Edisar, MT

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Atmospheric Modifications cont. 

Modification of the climate system by the introduction of “greenhouse” gases  

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Major gases are carbon dioxide, freons, methane Will lead to a warmer earth, and probably increase number and severity of major storms May affect short and medium term climate, and may modify the areas in which food can be grown


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Hydrological Modifications 

Diagram shows a local example of the hydrological cycle


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Hydrological Cycle Modifications   

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Withdrawal of water Pollution of water Impoundment of water (dams) Modifications in erosion and depositional rates  

Silting of rivers and estuaries Increased erosion below dams © By Dr. Muhammad Edisar, MT

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Biosphere Modifications 

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Mobilization 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.


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Biosphere Modifications cont. 

Human activities change natural environment 

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Often results in changes if species distribution, especially in loss of biological diversity (biodiversity) Rapid expansion of urban and suburban areas decreases available habitat Deforestation Expansion of farming into marginal environments Land use that is insensitive to long term changes 

Salinization


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Results of Environmental Change 

Species reduction 

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Mass 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


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Natural Events 

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Natural events often lead to mass mortality in many species - extinction may occur in severely geographically restricted species Examples: 

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Earthquakes Volcanoes Hurricanes Small meteorite impacts


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Overview   

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Geologic Time Movements of the Continents Earth Materials Tectonic Forces Weathering and Erosion Processes Erosional Agents and Deposition


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Geologic Time

Pretend the age of the earth (4.6+ billion years) is compressed into one calendar year.

January 1 - Earth and planets formed Early March - liquid water stands in pools. Late March - earliest life July - oxygen is important part of atmosphere October 25 - multicellular organisms Late November - plants and animals abundant December 15 to 25 - dinosaurs arise and disappear 11:20 pm, December 31 - Humans appear One second before midnight - Automobile invented © By Dr. Muhammad Edisar, MT 64

Formation of the Earth‟s Interior 

@5 bya, plantesimals (meterorites,icy comets) collide  heat released

(Kinetic energy to thermal energy)

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Entire planet melts (still cooling today) Gravity sorts materials by density  

Fe in center Si and O compounds towards surface


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The Upper Mantle and Crust 

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Crust (5 mi for ocean, 25 mi for continents) Dense iron-rich basalts (mafic) make up ocean floor  Fe, Silica, magnesium Silica- rich rock makes up the continents (felsic)  Silica, aluminum


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The Earth‟s Interior 

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General trends: temperature, density Horizon composition, behavior

© By Dr. km Muhammad Edisar, MT miles) Distance: 6730 (3963

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What is „tectonics‟? 

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From Greek „tektonikus‟ meaning building or construction Plate tectonics refers to the process of plate formation, movement, and destruction.


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What is a „Plate?‟

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Lithospheric plate: crust + upper mantle Aesthenosphere: plastic mantle © By Dr. Muhammad Edisar, MT

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History of Plate Tectonics 

„Fit‟ of coastlines recognized early 

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Sir Francis Bacon (1600s)

No mechanism for motion


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1915 Alfred Wegener proposes theory of continental drift. Supercontinent Pangaea („all-earth‟) [225mya]. Fragmentation and drift to current positions.


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Plate Movement History


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Wegner‟s evidence 

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Fit of continents Fossil plants, animals, rock types / geology  

match on opposite shores deposits inconsistent with current geography


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Striking Match of Biological Regions


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Striking Match of Geologic Regions


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Problem with continental drift? 

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No sound mechanism for the „drift‟! Wegner hypothesizes spin of earth or tides…..


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New theory for motion: Arthur Holmes (1930s) 

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thermal convective cells in the upper mantle (aesthenosphere) theory is largely ignored


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


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Sea Floor Spreading


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Plate Tectonics Theory 

Continental Drift + Sea Floor Spreading + new data  Theory of Plate Tectonics


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Plate Tectonics Theory 

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Plate boundaries: main location for Earth‟s volcanic and earthquake activity. This is main place where mountains are created. Type of plate boundary determines activity. 3 types 

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diverging (spreading) converging (colliding) transform (sliding past each other)


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Crustal Processes 

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Destruction (subduction) Creation (volcanism ) Alteration / deformation (folding and faulting)


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Geography of the Plates

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7 major plates; several minor plates Small plates / ©boundaries still unknown By Dr. Muhammad Edisar, MT

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Plate Margins: how do we know? 

Marked by volcanic and tectonic activity


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Divergent Plate Boundaries

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Landscape features: 

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land: rift valleys, volcanic mountains, thinning crust ocean/sea: rift valleys, mountain ranges


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Divergent Plate Boundaries 

Examples: 

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Atlantic Mid-Oceanic Ridge Red Sea Rift valleys of eastern Africa


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Convergent Plate Boundaries 

Activity: 

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subduction; shallow to deep earthquakes; volcanism (continental)

Features: 

ocean trench; explosive volcanic mtns on continental margin


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Earth Materials

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Three major rock types   

Igneous Sedimentary Metamorphic


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Igneous Rocks

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Igneous (ignus = fire) Formed from the cooling of molten rock (magma/lava), a process called crystallization. 

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Slow cooling  larger crystals > dense rock Rapid cooling  small crystals > lighter rock © By Dr. Muhammad Edisar, MT

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Two classes of igneous rocks  

intrusive: formed inside the Earth extrusive: formed at Earth‟s surface


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Igneous Intrusive Rocks Cools slowly (thousands of years)  Visible crystals  Examples - granite - diorite - gabbro 


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Igneous Extrusive Rocks Cools rapidly - exposed to surface  No visible crystals  Examples - rhyolite - andesite -basalt 


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Some unique rock types

 Pumice (vesicular) - sometimes so light it floats!

Obsidian  

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glassy, „curved‟ fracturing used for arrowheads by Native Americans


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Typical Igneous Intrusions

Know: Batholith and Dike © By Dr. Muhammad Edisar, MT

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Exposed Batholiths

Sierra Nevada, CA © By Dr. Muhammad Edisar, MT

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Sills and Dikes

Dike: Grand Canyon, AZ

Dike: Coast Ranges, BC

Granite sill in schist


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Sills and Dikes


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Igneous Extrusive Landscapes

Volcanic cones, obsidian flow: Mono Craters, CA

Volcanic neck and dike: Shiprock, NM


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Sedimentary Rocks


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Sedimentary Rocks Relative Abundance by Type

Compaction

Cementing

Formation


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Limestone (CaCO3)

Shale (fine grains)

Sandstone (larger grains)© By Dr. Muhammad Edisar, MT

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Where do Sedimentary Rocks Form? Marine environments

Terrestrial environments (non-marine) 

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Rivers and floodplains (fluvial environment)

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Lakes Deserts (aeolian environment)

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Continental shelf Continental slope and rise (deep sea fans) Abyssal plain

Beach and barrier islands


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Metamorphic Rocks or That‟s very Gneiss, but I don‟t give a Schist! Schist (narrow foliation)

Gneiss (broad foliation) © By Dr. Muhammad Edisar, MT

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Which Type? © By Dr. Muhammad Edisar, MT

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Which Type? Sedimentary - limestone and shale © By Dr. Muhammad Edisar, MT

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What type? © By Dr. Muhammad Edisar, MT

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What type?

Metamorphic - Amitsoq Gneiss, Greenland, © By Dr. Muhammad Edisar, MTOldest known rocks 109


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What type? Sedimentary - Sandstone in Utah© By Dr. Muhammad Edisar, MT

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What type? Extrusive Igneous Reunion S. MT Pacific © By Dr. Island, Muhammad Edisar,

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Morro Rock, CA


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Devil’s Tower, Wyoming

Morro Rock, CA

What type? Intrusive Igneous © By Dr. Muhammad Edisar, MT

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The Rock Cycle


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FI-6121 System Fisis Bumi Lecturer: Dr.M.Edisar, MT

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