Transcript Plate Tectonics

Plate Tectonics
Earth’s Layers
The Earth's rocky
outer crust solidified
billions of years ago,
soon after the Earth
formed.
This crust is not a
solid shell; it is broken
up into huge, thick
plates that drift atop
the soft, underlying
mantle.
The Crust
• Outermost layer
• 5 – 100 km thick
• Made of Oxygen, Silicon, Aluminum
The Mantle
• Layer of Earth
between the crust
and the core
• Contains most of the
Earth’s mass
• Has more
magnesium and less
aluminum and
silicon than the crust
• Is denser than the
crust
The Core
• Below the mantle
and to the center of
the Earth
• Believed to be mostly
Iron, smaller
amounts of Nickel,
almost no Oxygen,
Silicon, Aluminum, or
Magnesium
Tectonic Plates
Plate Tectonics
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Greek – “tektonikos” of a builder
Pieces of the lithosphere that move around
Fit together like jigsaw puzzles.
Float on top of mantle similar to ice cubes
in a bowl of water.
Drifting Continents Theory
• Wegener suggested that a supercontinent he
called Pangaea had existed in the past.
• It broke up starting 200 million years ago, and
the pieces ``drifted'' to their present positions.
• He cited the fit of South America and Africa,
ancient climate similarities, fossil evidence
(such as the fern Glossopteris and
mesosaurus), and similarity of rock structures.
Wegener ‘s hypothesis
• All continents were once together in a single
landmass and have since drifted apart.
• In 1915, Wegener published a book called the
“Origin of Continents and Oceans.”
Continental Drift
Alfred Wegener 1900’s
Continents were once a single
land mass that drifted apart.
Fossils of the same plants and
animals are found on different
continents
Called this supercontinent
Pangea, Greek for “all Earth”
300 Million years ago
Split again – Laurasia &
Godwin 180 million years ago
http://members.enchantedlearning.com/subjects/astronomy/planets/earth/Continents.shtml
Evidence of Pangaea
Evidence of Pangaea
• Fossil or any trace of an ancient organism.
• Fossil preserve in rocks.
• Glossopteris ( fernlike plant ) lived 250
million years ago.
• Freshwater reptiles (Mesosaurus and
Lystrosaurus )
Evidence of Pangaea
• Climate , as continents move toward the
poles, its climate is colder.
• As continents move toward the equator, its
climate gets warmer.
• Fossils of tropical plants were found in the
Arctic Ocean. ( Spitsbergen)
Sea Floor Spreading
Sea Floor Spreading
• Mid Ocean Ridges – underwater mountain
chains that run through the Earth’s Basins.
• Magma rises to the surface and solidifies
and new crust forms.
• Older Crust is pushed
farther away from the ridge.
• MOR lie under thousands
of meters of water.
Sea Floor Spreading
• Mid- ocean ridges continually add new
material ( CRUST ) to the ocean floor.
• Subduction is a process by which the ocean
floor sinks beneath a deep ocean trench and
back into the mantle again.
How Plates Move
http://pubs.usgs.gov/gip/dynamic/unanswered.html
Different Types of Boundaries
http://pubs.usgs.gov/gip/dynamic/understanding.html
Divergent Boundary –
Arabian and African Plates
Divergent Boundary –
Iceland
http://pubs.usgs.gov/gip/dynamic/understanding.html
Divergent Boundary - Oceanic
http://www.geology.com
Divergent Boundary - Continental
http://www.geology.com
Convergent Boundary – Indian and Eurasian Plates
Convergent Boundary – Oceanic & Continental
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Convergent Boundary – Oceanic & Oceanic
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Convergent Boundaries - Continental
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Transform Boundary – San Andreas Fault
www.geology.com
Fault
Trench
Puerto Rico Trench
Depth 800 m.
Length 8,000 m.
Rift Valley
Rift Valley
Theory of Plate Tectonics
• Earth’s plates are in slow constant motion,
driven by convection currents in the mantle.
Boundaries
Divergent
Boundaries
Convergent
Boundaries
Transform
Boundaries
Form
Crust pulling
apart
Valleys
Collision of
plates
Volcanoes
Moving together
Plates shift or
slip past each
other
Earthquakes
Review
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Name the 3 main layers of the Earth
What is a tectonic plate?
What was Pangaea?
What is Sea-Floor spreading?
Name the three different types of plate
boundaries and one location on Earth for each
one.