Transcript Slide 1

CH 9 PLATE TECTONICS
Roots:
Derm = skin (dermatitis)
Diplo = two (diploid)
Dis – away (disappear)
Dia = through (diagonal)
Dict = speak (dictate)
Domin = master (dominate)
Don = give (donation)
Duct = lead (conduct)
Du = two (duplicate)
Dur = lasting (durable)
Past or Future?
Future Plates:
http://earth.rice.edu/MTPE/geo/geosphere/topics/plate_tectonics/plate_future.mov
“Alfred! ALFRED! ALFRED WEGENER!”
Do you think when Alfred’s mom called him
in for dinner she had even the slightest idea
what a monumental effect her son would
have on the world as we understand it?
Alfred grew up to develop the
hypothesis of CONTINENTAL DRIFT.
He proposed that there had been a
supercontinent in Earth’s past and he
named it PANGAEA.
Evidence for Continental Drift:
The Continental Puzzle!
Evidence:
The continents fit
together like a
mega-puzzle.
Bullard Fit of Continents: http://www.wwnorton.com/college/geo/egeo/animations/ch2.htm
ACTIVITY: Making Pangaea puzzles.
Evidence for Continental Drift:
Fossils!
Breaking up is so hard to do!
“We need to talk…”
Pangaea breakup (slow-mo)
http://www.agci.org/classroom/geosphere/index.php
Continental Drift as Linked to Paleologic Time Scale
http://www.wiley.com/college/strahler/0471480533/animations/ch13_animations/animation3.html
Evidence for Continental Drift:
Continuous Mountains!
Mountain Ranges:
Ranges of mountains
that stretch across
multiple continents
that once were
attached.
These mountains
have the same rocks
and composition.
Grenville Orogeny
Evidence for Continental Drift:
Continuous Climates!
Wegener is rejected!
Wegener couldn’t explain the
mechanism (what was the force)
that allowed the plates to move.
A few scientists continued to
search for answers.
?
Evidence for Continental Drift:
Paleomagnetism!
1. Magnetic iron-rich
rocks heat up.
2. Lose their magnetism.
3. Cool down.
4. Become re-magnetic in
a direction parallel to
the existing magnetic
field around earth.
Magnetic Reversals: http://www.wwnorton.com/college/geo/egeo/animations/ch2.htm
Pg 266 Figure 17
Normal polarity
= when rocks show
the same
magnetism as the
current magnetic
field.
Reverse polarity
= when rocks show
opposite
magnetism to the
current magnetic
field.
Evidence for Continental Drift:
Earthquake Patterns!
Relationship between
deep focus
earthquakes and
ocean trenches.
Pg 267 Figure 18
1. Earthquakes are produced during subduction where rocks are
weak.
2. Shallow-focus quakes are produced in the weak rock as the
descending plate sinks.
3. As the descending plate (and weak rock section) goes deeper the
earthquake foci become deeper.
4. No earthquakes have been produced below 700 km. This is where
the rock begins to soften and melt.
Evidence for Continental Drift:
Ocean Drilling!
The Deep Sea
Drilling Project
1968-1983
The Glomar Challenger
drilled into the ocean floor.
Youngest rocks are
closest to the ridge.
Older
Young
Oldest
Evidence for Continental Drift:
Hot Spots!
The formation of hot spot
islands in a chain that
corresponds with the
movement of the plate.
Formation of Hawaiian Island Chain
http://www.teachersdomain.org/resourc
e/ess05.sci.ess.earthsys.hawaii/rm
By 1968, a new theory was developed –
Plate Tectonics.
Hawaii
Divergent = separating
Convergent = coming
together
Transform = sliding
past each other
Animated Plate Boundaries (shows divergent, convergent, and transform)
http://www.seed.slb.com/subcontent.aspx?id=5046
Seafloor Spreading = the process by which plate tectonics
produces new oceanic lithosphere.
Pg 259 Figure 9
• Upwarping occurs
• Rift valley is created
• Linear sea developes
• Oceanic ridge builds
• Continents drift apart
- Averages 5 cm/yr
- All of Earth’s oceans could have been created within the last
200 million years. (Oldest found is 180 my)
Sea Floor Spreading & Formation of Oceanic Crust:
http://www.wwnorton.com/college/geo/egeo/animations/ch2.htm
HSW: Earth Science: The Spreading Seafloor Time: 04:01
Iceland
Divergent Boundaries = where plates move away from
each other
Iberia
iceland
Basic Plate Boundaries: http://www.wwnorton.com/college/geo/egeo/animations/ch2.htm
Continental Rifts = areas where spreading develops
within a continent.
East African Rift Valley
The Process of Rifting:
http://www.wwnorton.com/college/geo/egeo/animations/ch2.htm
Convergent Boundaries = where plates come together
Ocean – Continent
Subduction Zone:
Where an ocean plate
is forced below a
continental plate.
Continental
Volcanic Arc = where
volcanic mountains are
created due to
subduction.
Basic Plate Boundaries & the Process of Subduction:
http://www.wwnorton.com/college/geo/egeo/animations/ch2.htm
Andes
Convergent Boundaries:
Ocean – Ocean:
Where two ocean plates collide.
Island Arc Formation:
http://esminfo.prenhall.co
m/science/geoanimations/
animations/35_VolcanicAct
.html
Aleutian Islands
Continent – Continent
Where two continental plates collide.
Himalayas
Continental plates
are buoyant so neither wants to subduct below
the other. As a result they simply collide and push up mountains.
Formation of Himalayas:
http://www.classzone.com/books/earth_science/terc/content/visualizations/es1105/es1105page01.cfm?chapter_no=visual
ization
Transform Boundaries = where plates slide past each other
Basic Plate Boundaries & Transform Faults:
http://www.wwnorton.com/college/geo/egeo/animations/ch2.htm
Why do the Tectonic Plates Move?
Main Reason: Convection.
Convection in a pot of water.
Convection around a heater.
Convection at the sea shore.
Why do the Tectonic Plates Move?
Slab-Pull = downward
movement of
convectional flow.
Ridge-Push = sliding
down of sides of ridge
and pushing outward
from the ridge.
Flash: Continents Adrift