Download Presentation

Chapter 7
What are the 3 Major Zones of
the Earth?
What is the CRUST?
• Outer layer of Earth
• Thickness: 5-70 km
• Thin, rocky
• Divided into
OCEANIC and
CONTINENTAL crust
What are the types of
Earth’s Crust?
• Oceanic
Crust –
Made up of
material on
the ocean
floor
• Continental
Crust –
Made up of
continental
landmasses.
What is the MANTLE?
• Layer of Earth between
crust and core
• Thickness: 2,900 km
• Solid, rocky,
• Magma, capable of
flowing
• Plastic
What is the CORE?
•
•
•
•
Center of Earth
Thickness: 3,500 km
Solid and liquid
Divided into 2 layers:
– OUTER core
• Liquid
• 2,260 km thick
– INNER core
• Solid…WHY?
• 1,220 km thick
What are the physical layers of the
Earth?
• The Earth is divided into 5 physical layers.
– Lithosphere
– Asthenosphere
– Mesosphere
– Outer core
– Inner core
What is the Lithosphere?
• The outermost, rigid layer of the Earth
• Composed of the crust and upper part of
the mantle. (15-300km)
• Divided into parts called the tectonic plates
that move in respect to each other.
What is the asthenosphere?
• Plastic layer of the mantle on which the
tectonic plates move. (250km thick)
What is the mesosphere?
• The lower part of the mantle…it is
extremely strong. It extends all the way to
the core…(2550km thick).
What are tectonic plates?
• Pieces of the lithosphere that move
around on top of the asthenosphere. It is
like a big jigsaw puzzle.
• There are 10 major tectonic plates…we
live on the North American Plate
 What
is Wegener’s
Continental Drift
Hypothesis? states that the
continents had once been joined to
form a single supercontinentPangaea, began to break apart 200
million years ago and form the
present landmasses. There was one
sea called Panthalassa “all
seas”…Pangaea existed during the
end of the Paleozoic era and end of
Mesozoic era.
What are the evidences of
Continental Drift?
•
•
•
•
Continental Puzzle
Fossil
Geological
Climatic
Breakup of Pangaea
Continental Puzzle
Figure 1
A Curious Fit
This map shows the best fit
of South America and
Africa at a depth of about
900 meters. The areas
where continents overlap
appear in brown.
Inferring Why are there
areas of
overlap?
Fossil
Identical fossil remains of Mesosaurus, a small,
extinct land reptile that lived 270 million years
ago, has been found in both eastern South
America and western Africa. These reptiles
could not have swum across the Atlantic Ocean.
Geological
Matching Mountain Ranges
Geological
Climatic
Ancient Glaciers grooves (shown by
arrows) in present day structures)
Gondwana Reconstruction of Southern
hemisphere super continent. Notice how ring
of glaciers match the patterns of a polar ice
Glacier Evidence
"Pangea Ultima" will form 250 million years in the
Future
What is the theory of
plate tectonics?
Earth’s surface consists
of a number of rigid, but
moving pieces called plates
Theory of Plate Tectonics:
Theory that helps explain
the formation and
movements of these plates
What happens when convection
currents move away from one
another?
• New material moves to
Earth’s surface
• Pushes older material aside
• Lithospheric plates move apart
Where cooler, denser
currents are sinking
• Lithospheric plates are
pulled together!
What happens at Plate
Boundaries?
• Place where one plate is
moving relative to another
plate
• Belts where earthquakes and
volcanoes are located –
stress builds up along
boundary
What are the
Kinds of Plate
Boundaries?
1. Divergent boundaries
• Places where two lithospheric plates
are moving apart
• Contain mid-ocean ridges which have
deep valleys along entire length called
rift valleys
• As plates move apart, molten rock
rises and fills space between plates –
cools and hardens
(seafloor spreading)
• When spreading centers develop
within a continent, the landmass may
split into two or more smaller
segments, forming a continental rift.
Continental rift near Krafla,
Iceland
East African Rift Valley
2. Transform Fault
Boundaries
• Lithospheric plates are
sliding past one another
• Transform fault – break or
crack in the Earth’s crust
along which movements have
occurred
Example:
San
Andreas
Fault
3. Converging Boundaries
•Places where two
plates come together
•There are
3 types….
I.SUBDUCTION Zone
• When an ocean plate and
continental plate collide
• Ocean plate slides under
continental plate
• Forms deep-ocean trench and
continental volcanic arc
II. CONT. to CONT.
Convergence
• Two continental plates
collide
• Become crumpled and
uplifted
• Form mountain ranges
Collision of India and Asia
III. OCEANIC TO OCEANIC
Crust Convergence
• One plate is subducted, forms
trench
• Subducted plate melts
• Molten rock rises to surface
along trench
• Forms island chain called an
ISLAND ARC
Evidence of Plate Tectonics
•
•
•
•
•
Paleomagnetic
Seafloor Spreading
Earthquake Patterns
Ocean Drilling
Hot Spots
 What is Paleomagnetism?
Paleomagnetism: rocks formed
millions of years ago show the
location of the magnetic poles at
the time of their formation.
• Normal polarity—when rocks show the
same magnetism as the present magnetism
field
• Reverse polarity—when rocks show the
opposite magnetism as the present
magnetism field
Paleomagnetism Preserved
in Lava Flows
Polarity of the Ocean Crust
Let’s go to this website and review!
CLICK HERE>>>
http://www.pbs.org/wgbh/aso/tryit/tectonics/#
Click on Plate Tectonics Activity (with a yellow arrow)
when you get there!
Here it is – all in one big picture…
Can you pick out the types
of Plate Boundaries?
Were you right?