Transcript Wegner*s Theory Of Continental Drift :

is the movement of the earths continents
relative to each other by appearing to drift
across the ocean bed .
 Evidence : Evidence for the movement of
continents on tectonic plates is now
extensive similar plant and animal fossils are
found around different continent shores and
may once have been joined together
 Problems with theory : one problem was that
plausible driving force was missing and it
didn’t help that wegner wasn’t a geologist.
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Supercontinent theory : that continents will move
farther apart as years pass .
Supercontinent Cycle : is the quasi – periodic
aggregation and dispersal of earths continental crust
Panthalassa means all seas ; pangaea was a
supercontient that existed in during the late
paleozoic and mesozoic eras
Accretion : (astrophysics) which material is added to
a tectonic plate or landmasses .
Rifting : is a linear zone where the Earths Crust and
lithosphere is are being pulled apart .
How plate movement alter climates and evolution ?
The climates adapt as the continents move . For
example Antarctica was once close to the equator
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Lithosphere : is the rigid outermost shell of a rocky planet .
Asthenosphere : is the highly viscous mechanically weak
and deforming region of the upper mantle of the earth .
How plates move ; because of high temperatures and
immense pressures .
Three types of plate boundaries; Divergent boundaries ,
Convergent boundaries , Transform boundaries .
Isostatsy : term used in geology to refer to the state of
gravitational equilibrium between the earths lithosphere
and asthenosphere .
Isotactic Adjustments : is the rise of land masses that were
depressed by huge pieces of ice sheets .
Stress : The state of stress in the lithosphere provides strong
constraints on the forces acting on the plates .
Lands forms; ( mid - ocean ridges )
where new oceanic crust if formed
formed through volcanic activity than
gradually moves away from the ridge .
Red sea is an example of landforms the
process starts with heating at the base
of the continental crust which causes it
becomes more plastic and less dense.
Magnetic reversals ; also known as flip , is
the process which the north pole is
transformed into the south pole and the
south becomes the north , the Earth's
magnetic field has undergone numerous
reversals of polarity.
 Magnetic Symmetry ; At the mid ocean
ridge the oceanic plates are separating
taking half of the lava on either side over
time the magnetic poles move around.
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Related landforms ; were plates
generally occur in places where
the lithosphere is being stretched .
They also can be found in deltas at
the rear edges of huge gravitation .
 Examples ; very low-angle normal
faults , active normal faults can be
shown to dip at angles steeper
than 50 degree
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Subduction zones ;
Continental & oceanic crust :Continental crust is the
layer of igneous , sedimentary , and metamorphic rock
which forms continents . & oceanic crust is the part of
earths lithosphere that surfaces in the oceans basins .
Landforms produced : stretches the landforms above
the surrounding land in an limited area In a form of a
peak .
Examples : folded mountains , fault block mountains ,
dome mountains , and plateau mountains
Oceanic & oceanic crust : the pacific ring of fire is also
a result of convergent boundaries in the
Ocean
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Volcano : is an opening in a planets
surface which allows hot magma volcanic
ash and gases to escape from the magma
chamber below the surface.
 The most common perception of a volcano
is of a conical mountain
 Major zones : being part of the Ring of Fire ;
the ring of fire is apart with the edges of
one of the world's main tectonic plates,
contains over 450 volcanoes has
approximately 75 percent of the worlds
active volcanoes.
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Viscosity : is a measure of the resistance
of a fluid which is being deformed by
either shear stress or tensile stress.
 How does magma content produce
explosive eruptions : gas gives magma
the explosive character the gas forms a
separate vapor phases when pressure is
decreased .
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Shield volcanoes : is a type of volcano
built of entirely of fluid lava flows .
 Examples : The Hawaiian shield
volcanoes are the most famous
examples
 Mauna Kea ; Mauna Loa ; Hualalai ;
Kohala are the 4 volcanoes that happen
in hawaii
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Are found on the flanks of shield
volcanoes . Examples :
 amples are SP Crater located in the San
range
Francisco Mountain range .
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form when runny lava escapes through a
fissure and flows down a long way .
 Examples : Andesite magma (the most
common but not the only magma type
tends to form composite cones.
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are ones where the diameter of the
circular to oval crater exceeds 1 mile
long .
 Examples :Crater Lake in Oregon was
created when a volcano detonated
around 10,000 years ago. The volcano
Kilauea of Hawaii has a magma
chamber by large lava flows
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Picture of a volcano
Erupting :
video
http://video.nationalgeographic.com/vide
o/environment/environment-naturaldisasters/volcanoes/volcano-lava/
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Continental and continental crust : is the
layer of igneous , sedimentary ,
metamorphic rocks .
 Compression & uplift : compression the
result of the subjection of a material to
compressive stress ; uplift :as one plate goes
down another goes up .
 Landforms produced ; folded mountains
worlds largest mountain range
 Plateaus not formed by internal activity ;
Dome is amount of melted rock (magma)
pushing its way up under the earth
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Reverse Faults : they result in occur in faults
undergoing compression
Strike – Slip Faults : A dislocation caused by a slipping
of rock masses along a plane of facture also the
dislocates structure resulting from such slipping.
Tension : is the pulling force exerted by a string,
cable, chain, or similar solid object on another
Sheer Stress : is the component of stress with a cross
section
Fault Block Mountains ; Sierra Nevada mountains
Grabens : depressed block of land bordered by
parallel faults
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Elastic Rebound : a theory of earthquakes that
envisages gradual deformation of the fault zone
without fault slippage until friction is overcome , when
the fault suddenly slips to produce the earthquake .
Seismology ; Seismograph : are instruments that
measure motions of the ground including those of
seismic waves generated by earthquakes volcanic
eruptions, and other seismic sources.
Focus :an earthquakes underground point of origin or
hypocenter
Epicenter : is the point on the Earth's surface that is
directly above the hypocenter or can earthquake or
underground explosion had started
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Body waves : travel through the interior
of the Earth . They create ray paths
refracted by the varying density and of
the Earth's interior. The density and
modulus vary according to temperature,
composition, and phase.
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Primary waves are compressional waves
that are longitudinal in nature. P waves
are pressure waves that travel faster
than other waves through the earth to
arrive at seismograph stations first hence
the name "Primary". These waves can
travel through any type of material,
including fluids, and can travel at nearly
twice the speed of S waves.
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Secondary waves (S-waves) are shear
waves that are transverse in nature.
These waves arrive at seismograph
stations after the faster moving P waves
during an earthquake and displace the
ground perpendicular to the direction of
propagation.
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Surface waves also known as ( L waves )
are analogous to water waves and
travel along the Earth's surface. They
travel slower than body waves. They are
called surface waves because they
diminish as they get further from the
surface
Almost all earthquakes occur at the edges
of the crustal plates. The constant bumping,
grinding, and lateral movement along
crustal boundaries can create sudden
movements that result in earthquakes.
 convergent boundaries: subduction and
collision. subduction boundary is marked by
the oceanic crust of one plate that is being
pushed downward beneath the
continental or oceanic crust of another
plate
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a seismic scale used for measuring the intensity of an
earthquake
The lower degrees generally deal with the fact in which
the earthquake is felt by people. The higher numbers of
the scale are based on observed structural damage.
Modified Mercalli Intensity example :
Under 2.0 I
2.0 – 2.9 I – II
3.0 – 3.9 II – IV
4.0 – 4.9 IV – VI
5.0 – 5.9 VI – VIII
6.0 – 6.9 VII – X
7.0 – 9.9 VIII or higher
10.0 or higher X or higher
the relative size of an object
 Intensity : is a measure of the energy flux
 For example : take the energy density
the energy per unit volume and times it
by the velocity at which the energy is
moving.
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Are giant waves cause by an
earthquake .
 Examples : The volcanic eruption on
Santorini Greece A tsunami is assumed to
be the factor that caused the most
damage
 Persian attackers who tried to exploit an
unusual retreat of the water were
suddenly surprised by a great flood-tide .
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http://sfist.com/2009/04/13/live_footage
_from_1989_earthquake.php