CONTINENTAL DRIFT Father of this theory is Alfred Wegener.
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Untold Tragedies of Continental Drift!!
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CONTINENTAL DRIFT Wegener published his belief that the Earths
continents were once all joined together in a super continent
called Pangaea which means all land, in 1915. He then theorized
that Pangaea broke apart and the continental pieces drifted over
time into their present location.
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PANGAEA
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CONTINENTAL DRIFT
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ANOTHER VIEW OF DRIFT
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WHAT EVIDENCE DID WEGENER HAVE? Wegener provided four main
pieces of evidence to support his theory that the continents had
been drifting over time.
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4!!
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1. JIGSAW PUZZLE add to handout Wegener noticed that if we
could move present day continents around, several continents look
like they would fit together like pieces of a jigsaw puzzle.
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1. JIGSAW PUZZLE
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2. FOSSILS add to handout Wegener also found fossils of the
same plants and animals on different continents now separated by
vast oceans. They could only be found this way if the continents
had once been joined together.
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2. FOSSILS
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3. ROCK SEQUENCE add to handout Wegener also found that
mountain ranges have a similar sequence of type of rock and age on
both sides of the Atlantic Ocean, suggesting they were once part of
the same mountain range.
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3. ROCK SEQUENCE
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4. GLACIAL SCARS add to handout Wegener found evidence of
glacial scars left behind by giant ice sheets from the same time
period in Southern Africa, India, Australia, Antarctica and South
America.
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4. Glacial Scars Then Now...
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WHAT COULD MOVE THE CONTINENTS?
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WEGENERS WEAKNESS Unfortunately for Wegener, he could not
explain what force was powerful enough to move entire continents
around the planet to his scientific peers, so he did not get much
support for his theory on continental drift.
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WEGENERS EXPEDITION
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WEGENERS WEAKNESS Alfred Wegener died on expedition in
Greenland in 1930 still searching for answers to the question of
what force could be responsible for the movement of the
continents.
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ALFRED WEGENER 1880 - 1930
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GET READY TO BOOGY! http://www.youtube.com/watch?v=T1- cES1Ekto
Review: http://www.youtube.com/watch?v=_5q8 hzF9VVE (11 minutes)
http://www.youtube.com/watch?v=T1- cES1Ekto
http://www.youtube.com/watch?v=_5q8 hzF9VVE
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THEORY OF PLATE TECTONICS Though several scientists contributed
to this theory, the father of the Plate Tectonic theory was J. Tuzo
Wilson, a Canadian geophysicist
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J. Tuzo Wilson 1908-1993 (Father of Plate Tectonics)
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THEORY OF PLATE TECTONICS Advances in sonar and echo sounding
technology in the 1960s led to the development of the theory of
plate tectonics which validated but improved upon Wegeners earlier
theory of continental drift.
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PLATE TECTONICS This theory states that the Earths crust is
broken up into several pieces called plates that move over a layer
of hot magma (molten rock) in the mantle layer of the Earth, below
the crustal plates.
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Earths Plates
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PLATES This theory states that the earths crustal plates are
made up of two things: 1) Continental Crust which is much older and
less dense and 2) Oceanic Crust which is younger and more
dense
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Evidence to Support the Plate Tectonics Theory 1.) Magnetic
Anomalies magnetic particles in rocks of the ocean floor align
themselves with the magnetic poles. When the magnetic poles reverse
themselves every 100 000 years, so do the magnetic characteristics
in the rocks on the ocean floor. Ocean floor rocks show these
magnetic anomalies in a matching pattern on either side of the
Mid-Atlantic Ridge, supporting the idea that the sea floor is
spreading in opposite directions from the Ridge.
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Magnetic Anomalies Reverse Pattern Normal Pattern When the
magnetic pole is in the Southern Hemisphere the rocks show a record
of a reverse magnetic pattern. Mid-Atlantic Ridge
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Evidence to Support the Plate Tectonics Theory 2.) Plate
Boundaries scientists found that the global distribution of
earthquakes and volcanic activity helped to locate the edges of
tectonic plates. The Boundaries are found along the path of most
volcanic and earthquake activity sites.
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WHICH PLATE DO WE LIVE ON? The North-American Plate!
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CONVECTION CURRENTS The Earths crustal plates move due to
convection currents in the Asthenosphere layer of the upper
mantle.
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The Crust and Upper Mantle Heat from the core, causes magma in
the upper mantle to move.
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HOW CONVECTION WORKS As magma gets heated by the core it
becomes less dense and begins to rise. As it rises away from its
heat source, it then begins to cool down. The cooler magma becomes
more dense than surrounding material and then sinks towards the
core, where it gets re- heated. Hot magma rises again creating a
continuous movement called a convection current or cycle of moving
magma in the mantle.
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CONVECTION CURRENTS
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CONVEYOR BELT The continental and oceanic crust act like a
conveyor belt on top of this moving magma. Convection currents in
the mantle move the crustal plates i) towards each other
(converging and subducting), ii) away from each other (diverging)
and iii) side by side (transforming) past each other.
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PLATE MOVEMENT Mid-Atlantic Ridge
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CREATIVE FORCE Write examples on handout of the diagrams of
plate boundary movement Tectonic plate movement can be creative in
that it can create mountain ranges when plates collide such as the
Himalayas that border India, Nepal and Pakistan and the Rocky
Mountains in North America.
DESTRUCTIVE FORCE Plate movement can also be considered
destructive as plates that subduct (one plate dives below another)
can consume crustal rock and turn it back into magma with heat and
pressure.
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1.b) PLATE SUBDUCTION
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What happens next? When plates collide or subduct, they create
erupting volcanic mountains, and deep ocean trenches (a very deep
ditch on the ocean floor). Examples include the Andes Mountains on
the West coast of South America and the Mariana Trench, east of The
Philippines on the Pacific Ocean Floor.
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OCEAN TRENCH
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2.) PLATE DIVERGENCE (plates separating) When plates diverge or
separate, they move away from each other causing the crust in
between to stretch and become thin and brittle. This make it easy
for magma to rise up and create mid- ocean ridges or rift
valleys.
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OCEAN RIDGES (The Mid-Atlantic Ridge)
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3.) TRANSFORM PLATES Where plates slide past one another there
are transform plate boundaries. As the plates are jagged they get
stuck and pressure builds up, eventually breaking apart in an
earthquake.
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TRANSFORM (SLIDING) PLATES
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TRANSFORM BOUNDARY There is a major transform plate boundary in
California where the San Andreas Fault is located, along which
Earthquakes are common.
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SAN ANDREAS FAULT
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Where the Action is: THE PACIFIC RING OF FIRE
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THE PACIFIC RING OF FIRE The most active part of the planet for
Earthquake and Volcanic Activity is found along the Ring of Fire
which is mostly a subduction plate boundary found around the edges
of the Pacific Plate, where it comes into contact with continental
plates.
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IN A NUT-SHELL! The theory of Plate Tectonics helps to explain:
i) how the cooling and heating of magma creates convection
currents;
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IN A NUT-SHELL ii) convection currents move the continental and
oceanic crustal plates towards, away and side by side each
other;
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IN A NUT-SHELL iii) The movement of these crustal plates
creates mountain ranges, volcanic eruptions, ocean ridges and
trenches, rift valleys and earthquakes, all of which shape and
reshape our planet.
