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Transcript of Plate Tectonics. EARTH; once upon a time ce/terc/content/visualizations/es0806/es0806...
Plate Tectonics
EARTH; once upon a time
http://www.classzone.com/books/earth_science/terc/content/visualizations/es0806/es0806page01.cfm?chapter_no=visualization
How did it form to the current day earth?
Tectonics Plates
• Earth’s crust is now broken to several pieces
called crustal or tectonic plates
• Each plate has an average thickness of 100km
and is composed of both continental and
oceanic crust
• Plate movement results in various landform
appearance
Tectonics Plates
• 9 major plates have been identified:
Eurasian plate
Philippine plate
Indo-Australian plate
Pacific plate
North American plate
African plate
South American plate
Nazca plate
Antarctic plate
Causes of Plate
Movements• Convection currents in
the athenosphere
• Currents circulate near the
base of the lithosphere,
cause drag on the bottom
of the plates, causing them
to move over the surface of
the Earth. http://www.classzone.com/books/earth_science/terc/content/visualizations/es0805/es0805page01.cfm?chapter_no=visualization
• As the plates move, they interact with each other
at their boundaries.
• 3 types of boundaries:
Divergent Plate Boundaries
Convergent Plate Boundaries
Transform Fault Boundaries
Plate movements and boundaries
Divergent Plate Boundaries
Plate movements and boundaries
Convergent Plate Boundaries
Plate movements and boundaries
Transform Fault Boundaries
Plate movements and boundaries
Divergent Plate Boundaries
• Zones of Tension
• Occurs mostly beneath oceans, few occur within
continents
• Convection currents diverge (moving apart), the
plates are pulled apart
• Magma from mantle wells up to fill gap between
separating plates.
• Cooling and solidification of magma on earth’s
surface
• Constructive margins formed, where new sea floor
(ocean crust )is generated.
• New sea floor appears as series of ridges
• Sea floor spreading occurs
– As plate pulls apart again and new cracks appear,
more magma rises to fill gaps creating more sea
floor
Divergent Plate Boundaries
• Rocks found further away from ridge proves that new
sea floor is created continuously
• Example of divergent plate boundary : Mid-Atlantic
Ridge, East African Rift Valley
http://whs.moodledo.co.uk/file.php/1365/EarthSystems/Earth%20Systems/Rift%20Valleys%20to%20Oceans.swf
MAGMA
OLDER ROCKS YOUNGER ROCKS OLDER ROCKS
RIDGES
Divergent Plate Boundaries
• Zones of Compression
• Convection currents converge (coming
together), the plates come together
• Three types of convergent boundaries
Oceanic and Continental plate collide
Oceanic and Oceanic plates converge
Continental and Continental plates collide
Convergent Plate Boundaries
• Known as destructive margins
• Continental plate which is less dense will ride over
oceanic plate
• Oceanic plate Subducts (forced downwards the
mantle), forming a deep elongated trough (ocean
trench)
• Volcanoes form in subduction zone
• As oceanic plates sink deeper, it gradually melts and
becomes magmahttp://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=visualization
Oceanic-Continental
http://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=visualization
Oceanic-Continental
• Less dense oceanic plate ride over more dense
oceanic plate
• More dense oceanic plate subducts, formation of
ocean trench
• Magma is force through overriding oceanic plate,
forming a chain of volcanic islands
• Example: line of islands running from the Aleutians,
Japan and down through Philippines
Oceanic-OCEANIC
Oceanic-OCEANIC
• Collision results in massive land form
• No Subduction
• Fold Mountain Range tend to form
• Example: the Himalayan Fold Mountain Range
Continental-Continental
Continental-Continental
• Also known as conservative margins
• Two plates slide past each other
• Fault-line created
Fault-line
Continental PlateContinental
Plate or Oceanic Plate
Transform fault boundaries
• Example of a transform fault boundary is the San
Andreas Fault
http://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=visualization
Transform fault boundaries
Results of Plate Movements
• Folding and Faulting
• Earthquakes
• Volcanoes
• When 2 plates collide, the rock strata (layers) will
bend and warp as they are compressed
• Features of folding: Synclines (downfold) and
anticlines (upfold)
Folding
SYNCLINEANTICLINE
• Place where rock strata band over is called hinge
line
• The rock strata on either sides of the hinge is
called limbsLIMBS
LIMBS
HINGE LINE
Folding
• Types of fold :
• Symmetrical fold – both limbs of equal gradient
• Assymmetrical fold- one limb steeper than the other
• Recumbent fold- Limbs are nearly parallel
• Overthrust old- One limb pushed forward so forcefully
that the rocks may fracture, and it overrides the other
limb. When the overriding limb becomes detached
from the main fold, it is called a nappe
Folding
SYMMETRICAL ASYMMETRICAL NAPPERECUMBENT
Folding
• Large scale folding will lead to formation of Fold
Mountains
• Examples of fold mountains:
The Himalayas
The Andes
The Zagros of Iran
http://www.classzone.com/books/earth_science/terc/content/visualizations/es1105/es1105page01.cfm?chapter_no=visualization
Folding
• Displaces rocks along a crack or fault line
• Occurs in 3 ways:
• Normal fault
• Reverse fault
• Tear fault
• Can give rise to block mountains and rift valleys
Faulting
• When rock strata are under tension caused by
forces acting in opposite directions
• Tension causes the rock strata to stretch and
crack, developing a normal fault
• One block of land then moves down
(downthrown block) to form an escarpment
• Example: The Tenton Mountain in Wyoming
USA
Normal fault
NORMAL FAULTS
• When rock strata are compressed
• Forces pushing towards each other causes the rock
strata to fold, giving rise to reverse fault
• One block of land moves up (upthrown block)
against the direction of the fault, creating an
overhanging scarp
• The overhanging scarp collapses due to gravity,
weathering and erosion, and produce a gentler slope
• Example: Sierra Nevada Mountains of California
Reverse fault
RESULT FAULTS
• Also known as wrench fault or strike-slip
fault
• When plates slip past each other horizontally
• Tensional or compressional forces act on the
rock strata giving rise to tear faults
• Big tear faults are known as transcurrent
faults
• Example: San Andreas Fault in the United
States
Tear fault
TEAR FAULT
• Block raised between 2 parallel fault lines is
called a block mountain
• If surface is horizontal, it is termed as a horst
• if block is tilted, it is termed tilt block
• Examples of faulted blocks:
• Hawkes bay in New Zealand
Block Mountains
HORST
• Also known as a graben
• Formation can be due to:
land between two parallel lines sink
land on either side of the two parallel lines are
unpthrown above the central block of land
two plates pull apart
• Example:
The East African Rift Valley
The Red Sea
Rift valleys
GRABEN
http://www.iris.washington.edu/gifs/animations/faults.htm http://www.classzone.com/books/earth_science/terc/content/visualizations/es1103/es1103page01.cfm?chapter_no=visualization
• Vibrations in earth’s crust caused by sudden release of
energy
• Energy released in the form of seismic waves and
that radiate out from the epicentre
• Point below the epicentre is called the point of origin
where the earthquake originated from
http://www.pbs.org/wnet/savageearth/animations/earthquakes/index.html
Earthquakes
• Two types of seismic waves:
• P- waves (Compression waves)
alternately compress and release rocks in the direction
the waves are moving
• S- waves (Shear waves)
move rocks perpendicularly to the direction the waves
are moving
Earthquakes
http://www.classzone.com/books/earth_science/terc/content/visualizations/es1002/es1002page01.cfm?chapter_no=visualization
Earthquakes
• Major earthquake zones:
• Pacific Ring of Fire -Along the edge of the Pacific
Ocean
• Trans-Eurasian Belt –Where the Indo-Australian Plate
and African Plate meet the Eurasian Plate
Earthquakes
Earthquakes
http://www.classzone.com/books/earth_science/terc/content/visualizations/es1005/es1005page01.cfm?chapter_no=visualization http://www.classicalarchives.com/eq/
• Displacement of earth’s crust
• When earthquakes occur in the ocean floor:
Tsunamis (huge tidal waves)
• Devastation of cities and loss of lives
EFFECTS OF Earthquakes
MOUNT DOOMLORD OF THE RINGS
VOLCANOES
volcanoes
• Found along plate boundaries or hotspots
• Can be found on land or under water
• Volcanoes on land : often form flat cones and
the expulsions build up over the years.
• Volcanoes under water: often form rather
steep pillars and in due time break the ocean
surface in new islands.
volcanoes
• Vulcanicity: when magma is forced towards
earth’s surface from within the earth
• Hotspot volcanoes: where the location has
vulcanism for a long period of time
• Example of hotspot volcano: Java Island in
Indonesia
http://www.classzone.com/books/earth_science/terc/content/visualizations/es0904/es0904page01.cfm?chapter_no=visualization
volcanoes
• Most volcanoes on the land are formed at
destructive plate margins:
• Oceanic crust melt, reduced density force the
newly formed magma to rise.
• As magma rises it rises up through weak areas in
the continental crust, eventually erupting as one
or more volcanoes.
volcanoes
• For example, Mount St. Helens is found inland
from the margin between the oceanic Juan de
Fuca Plate and the continental North American
Plate.
volcanoes
http://www.classzone.com/books/earth_science/terc/content/visualizations/es0902/es0902page01.cfm?chapter_no=visualization
References.• http://www.lostrivers.ca/points/pangaea.gif • http://www.cotf.edu/ete/images/modules/msese/earthsysflr/EFPlateP2.gif • http://www.oera.net/How2/PlanetTexs/EarthMap_2500x1250.jpg • http://www2.jpl.nasa.gov/galileo/wedges/images/plat.gif• http://stloe.most.go.th/html/lo_index/LOcanada4/403/images/4_1.jpg• http://lacreekfreak.files.wordpress.com/2008/11/wsci_03_img0412-san-andreas-fault1.jpg• http://www.yosemite.ca.us/library/geologic_story_of_yosemite/images/28.jpg• http://geomaps.wr.usgs.gov/parks/pltec/ocnvsocn289x151.gif• http://www.adventure-india-tour.com/about-himalayas/gifs/himalayan-mountain-ranges.jpg• http://geomaps.wr.usgs.gov/parks/pltec/converge.html• http://dl.coastline.edu/classes/telecourses/geology100/IntroLecture_files/image005.jpg• http://depts.washington.edu/explore/images/maps/250px-Pangaea_continents.png• http://www.sedl.org/scimath/pasopartners/dinosaurs/continent2.gif• http://2.bp.blogspot.com/_osP51C3atIY/Rf7Z34zK7PI/AAAAAAAAAr4/F2WdWu92P0g/s200/oceanic-subd-ridge.png• http://www.emporia.edu/earthsci/amber/students/grunz/antsyn.gif• http://www.whoi.edu/cms/images/s-p_waves_73570.jpg• http://i243.photobucket.com/albums/ff24/terryhallinan/800px-Pacific_Ring_of_Fire-1-1.png• http://www.enchantedlearning.com/subjects/volcano/gifs/ringoffirecolor.GIF • http://facweb.bhc.edu/academics/science/harwoodr/GEOL101/study/Images/ReverseFault.gif• http://facweb.bhc.edu/academics/science/harwoodr/GEOL101/study/Images/HorstGraben_2.gif• http://www.geocities.com/yingzyingz/faulttear.gif• http://facweb.bhc.edu/academics/science/harwoodr/GEOL101/study/Images/NormalFault.gif• http://www.tinynet.com/faultimages/graben.gif• http://www.3mfuture.com/images/tsunami_wave_coming_now_too_late.jpg• http://depts.washington.edu/qrc/mht1.jpg• http://www.pacificislandtravel.com/nature_gallery/volcanoes2.gif• http://www.tolkienforums.com/Mount_Doom.jpg • http://www.malapascua.de/Volcanoe-Map/Mayon__Philippines/Vulkan_MAYON-3/Mayon_Volcano_Eruption_by_Night.jpg
The End.