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© By Dr. Muhammad Edisar, MT 1
FI-6121 System Fisis Bumi Lecturer: Dr.M.Edisar, MT
The Composition of the Earth
© By Dr. Muhammad Edisar, MT 3
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
4
Komposisi Bumi Bedasarkan:
Komposisi Kimia
Unsur-unsur utama
Sifat Fisis
© By Dr. Muhammad Edisar, MT
© By Dr. Muhammad Edisar, MT 5
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
© By Dr. Muhammad Edisar, MT 6
Batas Inti –mantle (CMB) didefinisikan oleh diskontinuitas Gutenberg
Zone dari 200 - 300 km, ditandai D11
© By Dr. Muhammad Edisar, MT 7
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 8
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.
© By Dr. Muhammad Edisar, MT 9
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, magnesiowüstite
© By Dr. Muhammad Edisar, MT 10
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
© By Dr. Muhammad Edisar, MT 11
Kerak (Crust)
Batas Mantle – Kerak dibangun oleh diskontinuitas Mohorovičić
Daerah ketebalannya dari 10 - 70 km
Terdiri dari dua jenis
1. Samudra
2. Benua
© By Dr. Muhammad Edisar, MT 12
Kerak Samudra 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 13
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 15
lithosphere
Kulit bagian luar dari Bumi yang Kaku (rigid)
Disusun dari :
Mantel Bagian Atas
Kerak Samudra
Kerak Benua
Ketebalannya 70 - 125 km
© By Dr. Muhammad Edisar, MT 16
asthenosphere
Daerah kulit bagian luar Bumi yang terletak dibawah lithosphere
Meluas sampai kedalaman ~ 220-km
Bersifat plastis
© By Dr. Muhammad Edisar, MT 18
Permukaan Bumi terbagi ke pada 12 plat utama
Plate bergerak secara horizontalterhadap satu sama lain
Plate “mengapung” atau“meluncur” diatas lapisan asthenosphere viskositas tinggi.
© By Dr. Muhammad Edisar, MT 19
Lempeng terdiri dari kerak samudra dan kerak benua
Aksi utama tektonik lempeng terjadi pada pinggiran lempeng
© By Dr. Muhammad Edisar, MT 20
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
© By Dr. Muhammad Edisar, MT 21
Volcanoes of the World (Smithsonian Institution Global Volcanism Program)
24
Lempeng Divergent
Batas penyebaran (Spreading)
Daerah healed “ kerak ” atau fissures
Contoh :
Rift Valley dari Afrika bagian timur
Mid-Atlantic ridge
Gunung api, gempabumi
© By Dr. Muhammad Edisar, MT
© By Dr. Muhammad Edisar, MT 28
Lempeng Convergent
Pada batas lempeng convergent respons terhadap tumbukan lempeng akan bervariasi dengan jenis kerak yang bersangkutan
Ada tiga kemungkinan kombinasi:
© By Dr. Muhammad Edisar, MT 29
Kerak samudra converging with kerak samudra:
Subduksi satu lempeng
Formasi dari sebuah busur kepulauan
Gunung api
Gempabumi
Contoh kepulauan Japanese
© By Dr. Muhammad Edisar, MT 31
Kerak samudra converging degan kerak benua :
Formasi dari rantai pegunungan
Gunung api
Gempa bumi
Contoh Pegunungan Andes
© By Dr. Muhammad Edisar, MT 33
Kerak benua converging dengan kerak benua :
Overriding dari satu lempeng
Formasi dari daerah pegunungan
Gempa bumi
Contoh Himalayas
© By Dr. Muhammad Edisar, MT 35
Transform Boundaries
“side-slip boundary”
create fault zones
earthquakes
example San Andreas
© By Dr. Muhammad Edisar, MT 41
Ecosphere
That part of the earth consisting of the atmosphere, hydrosphere, lithosphere, and biosphere
© By Dr. Muhammad Edisar, MT 42
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: Thermosphere > 80 km
Mesopause
Mesosphere 45 - 80 km
Stratopause
Stratosphere 12 - 45 km
Tropopause
Troposphere 0 -12 km
© By Dr. Muhammad Edisar, MT 43
Hydrosphere
Earth's water, in any physical state –
Gaseous
Liquid
Solid
© By Dr. Muhammad Edisar, MT 44
Lithosphere
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
© By Dr. Muhammad Edisar, MT 45
Interior of the Earth
Crust – 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)
© By Dr. Muhammad Edisar, MT 46
Biosphere
Interface layer between earth's crust, atmosphere, and hydrosphere where life is found
Includes the total ecosystem of the earth
© By Dr. Muhammad Edisar, MT 47
Ecosystem
Community of interacting organisms, of all species
Includes interactions of this community with the chemical and physical systems of earth
© By Dr. Muhammad Edisar, MT 48
Human Activities
Interact with the natural world, causing changes in the ecosystem
Changes vary in magnitude and temporal scale
© By Dr. Muhammad Edisar, MT 49
Environmental Issues
Changes in the ecosphere caused by:
Natural processes
Human activities
Often cause change
Affect the rate at which change occurs
Or both
© By Dr. Muhammad Edisar, MT 50
Changes By Other Species
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
© By Dr. Muhammad Edisar, MT 51
So What Makes Humans Different?
Humans are the first species to be aware of their influence
Humans assume, to some extent, responsibility for wise management of the planet
© By Dr. Muhammad Edisar, MT 52
Technology Improvements
During the last fifty years
Have greatly contributed to our awareness of environmental change
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 53
Examples of Technological Change
Satellite observations
Computational power
Rapid communication (Internet)
© By Dr. Muhammad Edisar, MT 54
Changes to the Ecosphere
Many examples of modification of ecospheric components have been described
Representative examples of these modifications are shown on the following slides
© By Dr. Muhammad Edisar, MT 55
Atmospheric Modifications
Depletion of ozone (O3) in the ozone layer (stratosphere) which affects UV light absorption 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 56
Atmospheric Modifications cont.
Modification of the climate system by the introduction of “greenhouse” gases
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
© By Dr. Muhammad Edisar, MT 57
Hydrological Modifications
Diagram shows a local example of the hydrological cycle
© By Dr. Muhammad Edisar, MT 58
Hydrological Cycle Modifications
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 59
Biosphere Modifications
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.
© By Dr. Muhammad Edisar, MT 60
Biosphere Modifications cont.
Human activities change natural environment 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
© By Dr. Muhammad Edisar, MT 61
Results of Environmental Change
Species reduction
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
© By Dr. Muhammad Edisar, MT 62
Natural Events
Natural events often lead to mass mortality in many species - extinction may occur in severely geographically restricted species
Examples:
Earthquakes
Volcanoes
Hurricanes
Small meteorite impacts
© By Dr. Muhammad Edisar, MT 63
Overview
Geologic Time
Movements of the Continents
Earth Materials
Tectonic Forces
Weathering and Erosion Processes
Erosional Agents and Deposition
© By Dr. Muhammad Edisar, MT 64
Geologic TimePretend 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 65
Formation of the Earth‟s 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 density
Fe in center
Si and O compounds towards surface
© By Dr. Muhammad Edisar, MT 66
The Upper Mantle and Crust
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
© By Dr. Muhammad Edisar, MT 67
General trends: temperature, density
Horizon composition, behavior
The Earth‟s Interior
Distance: 6730 km (3963 miles)
© By Dr. Muhammad Edisar, MT 68
What is „tectonics‟? From Greek „tektonikus‟
meaning building or construction
Plate tectonics refers to the process of plate formation, movement, and destruction.
© By Dr. Muhammad Edisar, MT 69
What is a „Plate?‟
Lithospheric plate: crust + upper mantle
Aesthenosphere: plastic mantle
© By Dr. Muhammad Edisar, MT 70
History of Plate Tectonics
„Fit‟ of coastlines recognized early
Sir Francis Bacon (1600s)
No mechanism for motion
© By Dr. Muhammad Edisar, MT 71
1915 Alfred Wegener proposes theory of continental drift.
Supercontinent Pangaea („all-earth‟) [225mya].
Fragmentation and drift to current positions.
© By Dr. Muhammad Edisar, MT 73
Wegner‟s evidence
Fit of continents
Fossil plants, animals, rock types / geology
match on opposite shores
deposits inconsistent with current geography
© By Dr. Muhammad Edisar, MT 76
History of Plate Tectonics Problem with continental drift?
No sound mechanism for the „drift‟!
Wegner hypothesizes spin of earth or tides…..
© By Dr. Muhammad Edisar, MT 77
History of Plate Tectonics New theory for motion: Arthur Holmes
(1930s)
thermal convective cells in the upper mantle (aesthenosphere)
theory is largely ignored
© By Dr. Muhammad Edisar, MT 78
History of Plate Tectonics
In the 1960s, Harry Hess and Robert Deitz (geophysicists) propose sea floor spreadingalong mid-oceanic ridges for plate motion.
© By Dr. Muhammad Edisar, MT 81
Plate Tectonics Theory Continental Drift + Sea Floor Spreading
+ new data Theory of Plate Tectonics
© By Dr. Muhammad Edisar, MT 82
Plate Tectonics Theory
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
diverging (spreading)
converging (colliding)
transform (sliding past each other)
© By Dr. Muhammad Edisar, MT 83
Crustal Processes
Destruction (subduction)
Creation (volcanism )
Alteration / deformation (folding and
faulting)
© By Dr. Muhammad Edisar, MT 84
Geography of the Plates
7 major plates; several minor plates
Small plates / boundaries still unknown
© By Dr. Muhammad Edisar, MT 85
Plate Margins: how do we know?
Marked by volcanic and tectonic activity
© By Dr. Muhammad Edisar, MT 86
Divergent Plate Boundaries
Landscape features:
land: rift valleys, volcanic mountains, thinning crust
ocean/sea: rift valleys,
mountain ranges
© By Dr. Muhammad Edisar, MT 87
Divergent Plate Boundaries
Examples:
Atlantic Mid-Oceanic Ridge
Red Sea
Rift valleys of eastern Africa
© By Dr. Muhammad Edisar, MT 88
Convergent Plate Boundaries Activity:
subduction; shallow to deep earthquakes; volcanism (continental)
Features:
ocean trench; explosive volcanic mtns on continental margin
© By Dr. Muhammad Edisar, MT 89
Earth Materials
Three major rock types Igneous
Sedimentary
Metamorphic
© By Dr. Muhammad Edisar, MT 90
Igneous Rocks
Igneous (ignus = fire)
Formed from the cooling of molten rock (magma/lava), a process called crystallization.
Slow cooling larger crystals > dense rock
Rapid cooling small crystals > lighter rock
© By Dr. Muhammad Edisar, MT 91
Two classes of igneous rocks
intrusive: formed inside the Earth
extrusive: formed at Earth‟s surface
© By Dr. Muhammad Edisar, MT 92
Igneous Intrusive Rocks Cools slowly (thousands of years)
Visible crystals
Examples
- granite - diorite - gabbro
© By Dr. Muhammad Edisar, MT 93
Igneous Extrusive Rocks Cools rapidly - exposed to surface
No visible crystals
Examples
- rhyolite - andesite -basalt
© By Dr. Muhammad Edisar, MT 94
Some unique rock types
Pumice (vesicular)
- sometimes so light it floats!
Obsidian
glassy, „curved‟ fracturing
used for arrowheads by Native Americans
© By Dr. Muhammad Edisar, MT 97
Sills and Dikes
Dike: Grand Canyon, AZ
Granite sill in schistDike: Coast Ranges, BC
© By Dr. Muhammad Edisar, MT 99
Igneous Extrusive Landscapes
Volcanic neck and dike: Shiprock, NM
Volcanic cones, obsidian flow: Mono Craters, CA
© By Dr. Muhammad Edisar, MT 101
Compaction Cementing
Sedimentary
Rocks
Formation
Relative Abundance by
Type
© By Dr. Muhammad Edisar, MT 103
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
© By Dr. Muhammad Edisar, MT 105
Metamorphic Rocks or That‟s very Gneiss, but I don‟t give a Schist!
Gneiss (broad foliation)
Schist (narrow foliation)
© By Dr. Muhammad Edisar, MT 109
What type? Metamorphic - Amitsoq
Gneiss, Greenland, Oldest known rocks