Download Plate tectonics 2014

Evidence of
Plate Tectonics
Sea Floor Spreading/
Continental Drift
https://www.youtube.com/watch?v=0mWQs1_L3fA
Convection in Earth’s Mantle
• Earth’s mantle acts like soup simmering in a
pot.
• Heat source = Earth’s
core
• Hot columns rise to the
asthenosphere
• Spread out and push
cooler material out of the
way.
• Cooler material sinks.
• The cycle continues over
and over again.
Theory of Continental Drift
• Scientist study the Earth and look for clues to its origin and
reasons why things occur/look as they do. Why are there
mountains and valleys? Why are the oceans deeper in one
place than another?
• Wegner came up with a hypothesis that all continents were
once a single landmass and since have drifted apart.
• He called this Pangaea
Theory of Continental Drift
• Found evidence from
– Puzzle-like fit
– Landforms (mountain ranges)
– Fossils (reptiles, plants)
– Climate (Coal in cool regions, deep
scratches from glaciers in South
Africa)
• Wegener could not prove his theory.
• He could not explain the force for how
the continents moved.
Sea-Floor Spreading-
Sea-Floor Spreading
Evidence of Sea-Floor Spreading
•
Molten Material
–
•
Found “pillow” rocks, that show molten
material have erupted again and again.
Magnetic Stripes
– Patterns in rock show a pole reversal
•
Drilling Samples
– Determined ages of rock
– Younger rocks at center of ridge
– Older rocks further away from ridge
•
http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/p_seafloorspreading.html
Convection in Earth’s Mantle
• Earth’s mantle acts like soup simmering in a
pot.
• Heat source = Earth’s
core
• Hot columns rise to the
asthenosphere
• Spread out and push
cooler material out of the
way.
• Cooler material sinks.
• The cycle continues over
and over again.
The Theory of Plate
Tectonics
• A theory that states that pieces of
Earth’s lithosphere (plates) are in
constant, slow motion, driven by
convection currents in the mantle.
Fun Fact
• The Pacific Ocean is Shrinking!
– Deep-ocean trenches are swallowing more
oceanic crust than the mid-ocean ridge can
produce.
• The Atlantic Ocean is Growing!
– This area only has a few short trenches, so
the spreading ocean floor has virtually
nowhere to go.
Plate tectonics
• Theory states the Earth’s crust is
divided into sections which float on a
plastic-like layer of the mantle
• Plates :sections of the Earth’s crust
• Lithosphere: the crust and upper
mantle (includes plates)
• Asthenosphere: plastic like layer that
the plates move over.
Divergent Boundaries
• A place where two plates move apart
Divergent plate boundary
• Plates move apart;
Gain crust as mantle
bubbles up
•
• Force is tension (pulled apart)
• Features:
–
–
–
–
Earthquakes
Mountains (volcanic mountains and islands)
Rift valley
Volcanoes
• Geographic Location: Mid Atlantic Ridge, Iceland, Great
Rift Valley in Africa, East Pacific Rise
Transform Boundaries
• A place where two plates slip past each
other.
Transform Boundary
• Two plates slide past
each other in opposite
direction
• Force is shearing
• Feature: Earthquakes, faults
– Since movement is side to side no
mountain ranges form and no volcanoes
•
Geographic location: California
An example of a Transform Boundaries
Convergent Boundaries
• A place where two plates collide
Procedure:
1. In your group of four, you should have
three people with candy. Two should have
two mini snickers and one should have
a fun size.
2. Choose a boundary type to model.
3. Using your notes from yesterday, decide how to model the
movement at this type of boundary using two minis and one fun six
bar. Then do it.
4. Identify the features each model showed.
At the end your group needs to decide which choice (two minis or
one fun size) is best and support that with evidence from the lab.
Convection Currents
– Caused by unequal distribution of heat.
Less dense material (hotter) rises, cooler
material sinks (relative to other material)
– Plates move as differences in density force
mantle to rise and fall
Convergent Boundary; Ocean to Continent
• Plates move together;
denser plate sinks
under the less dense plate
forming a subduction zone
• Crust is lost
• Force is compression
• Features: volcanic mountains, volcanic island
arcs, trenches, earthquakes
• Geographic location: Andes Mt range in S.
Am, Japanese Islands, Cascade Mountains
Convergent Plate Boundary:
Ocean to Ocean
• Plates move together;
denser plate sinks
under the less dense plate
forming a subduction zone
• Crust is lost
• Force is compression
• Features: Islands, island arcs (volcanic
mountains the rise about water),
earthquakes, trenches
• Geographic Locations: Mariana Islands
in Western Pacific
Convergent Plate Boundary:
Continent to continent
• Plates move together
• Neither plate goes under
the other because density
is similar…..No subduction occurs
• No volcanoes form; but crust is
lost because it moves upward
• Force is compression
• Feature: Mountains
• Geographic locations: Appalachian
Mountains, Himalaya Mt.
Example of a Convergent Boundary
Complete plate tectonic foldable
• Answers
– Section
– Section
– Section
– Section
– Section
– Section
– Section
two
three
four
five
six
seven
eight
Label the picture
Island Arcs
Rift valley
Volcanic
Mountains
trench
trench
TB
CB
Subduction
DB
CB
Subduction
Candy Boundary Activity
Does the size of the candy bar affect how features at
boundaries can be shown?
Materials:
Book: Chapter 5, 7
Six mini snickers or milky ways
Three fun size snickers or milky ways
Knife
Group work
• Fill in the chart
– Need book or computer
• Complete Candy Boundary Lab
– Peanut allergies?