Download Notes #5 Plate tectonics

Plate Tectonics
Notebook # 5
February 8, 2016
8.E.5A.4 Following these notes you will be able to construct
explanations for how the theory of plate tectonics accounts
for the motion of lithospheric plates, the geologic activities at
plate boundaries, and the changes in andform areas over
geologic time.
Quick facts about the Theory of Plate
Tectonics:
1. Explains the past and current movement
s of the rocks at Earth's surface
(lithospheric plates)
2. Provides the framework for
understanding the Earth's geologic history.
3. Plate movement is responsible for most
continental and ocean floor features
4. Plate movement is responsible for the
distribution of most rocks and minerals
within Earth's crust
5. Evidence supporting the theory of Plate
tectonics:
a. distribution of rock formation and
fossils
b. shapes of existing continents
c. ocean floor features
d. seismic and volcanic activity
* This evidence shows how Earth's plates
have
What is Plate Tectonics?
* Explains why large sections of Earth's crust move
* Explains how large sections of Earth's crust move
* Explains how Earth's features form
Lithospheric Plates:
large sections of Earth's crust
(crust and top layer of the mantle)
Continental Drift
* a hypothesis that was developed prior to
the theory of plate tectonics
* Earth's continents move on Earth's
surface
 Based on:
 
 * continent shape
 * fossil evidence
 * rock clues
 * climate clues
What did not support the hypothesis of
continental drift?
 * plate movement
*Plate movement lead to the theory of plate
tectonics.
Hypothesis Versus
Theory!!!!!
Hypothesis :
 an
educated prediction based on previous
knowledge
Theory:
 set of widely accepted explanations of
observations; a well-tested   explanation that is
consistent with all available evidence
  
A. Motion of
Lithospheric Plates
 * plates float on the upper part of the mantle
 *convection currents cause the asthenosphere
to flow slowly—carrying the   plates of the
lithosphere
 
 - convection currents: a circulation pattern in
which material is heated  and rises in one area,
then cools and sinks in  another area, flowing in
a continuous loop
  
- asthenosphere: top portion of the    mantle
late movement changes: 
 
 - sizes of Earth’s continents and oceans 
 
 -shapes of Earth’s continents and oceans 
 
 -positions of Earth’s continents and oceans
B. Geologic Activities
at Plate   
Boundaries
1. divergent boundary—
 
 *where 2 plates are moving apart
 
 *most are located along the mid-ocean ridge although they can
be found on land
 
 *new crust forms when magma pushes up and hardens in the
rift zone (between separating plates) (seafloor spreading)
* earthquakes occur as plates spread apart
*Rift Zone- is a feature of some volcanoes, especially shield
volcanoes, in which a linear series of fissures in the volcanic
edifice allows lava to be erupted from the volcano's flank instead
of from its summit
2. convergent boundary 
 *where 2 plates come together and collide
 
 *activity depends on the types of crust that meet

 *when 2 oceanic plates collide, one plate slides under the
other

 *when an oceanic plate collides with a continental plate, the
oceanic (dense) plate slides under the
  less-dense continental plate
-this forms a trench at the subduction zone
where crust is melted and recycled
-along these trenches, island arcs and
volcanic arcs can be created
  
 **when one plate slides under another some crust is
destroyed in this process
*2 continental plates converge, both plates buckle and push up
into mountain ranges or volanoes
* earthquakes occur as the plates collide
3. transform boundary—
 
 * where 2 plates slide past each other 
 
 * crust isn’t created or destroyed
 
 * earthquakes occur frequently here
C. Changes in Landform
Areas
Over Geologic Time
* plates move slowly (about 1 to 10 cm per year)
* Pangaea—large, ancient landmass made of all the
  
continents; at one time in geologic history the
continents were joined together in one large landmass
* when the continents continued to moved and split,
oceans formed and this continued until the landmasses
came to their current positions
* evidence of plate movements comes from:
-identical fossil formations found on separate
continents
-landform shapes and features
-identical rock formations found on separate
continents
-paleoclimate evidence (example: evidence of
warmer climates found in Antarctic
fossils)
* landmass changes can occur at ‘hot spots' within
lithospheric plates; volcanic activity occurs as magma
rises and leaks through the crust
 
* plates will continue to move and change
* landforms of Earth can be created or changed by
volcanic eruptions and mountain-building forces.
Hot Spots
* area where a column of hot material rises from deep
within a
planet's mantle and heats the lithosphere above it, often
causing volcanic
activity at the surface