Transcript File - MRS. STOTTS CHEMISTRY and NATURAL SCIENCE

Plate Tectonics
Chapter 10
POD
2/5/08
1. Summarize the theory of plate tectonics.
Using arrows to draw/label the three types
of plate boundaries. Give an example of
each.
Problem of the Day (POD)
1/30/08
1. Who proposed the theory of continental
drift. What mechanisms led to this theory
being accepted in the science community?
POD
2/1/08
1. How are tectonic plate boundaries related
to earthquakes? What are the three types
of plate boundaries?
Section 1
Objectives
Summarize Wegener's hypothesis of continental drift.
Describe the process of sea-floor spreading.
Identify how paleomagnetism provides support for the
idea of sea-floor spreading.
Explain how sea-floor spreading provides a mechanism
for continental drift.
Wegner’s Hypothesis
1912 German Scientist
Proposed Continental Drift
Supercontinent- began
breaking into smaller
continents 250 million years
ago
Over millions of years
continents drifted to present
locations
Evidence to Support
Fossil Evidence
Fossils of same plant and
animals found in areas that
had once been connected
Rock Formations
Ages and types of rocks in
coastal regions matched closely
Western Africa and Eastern South
America
Evidence to Support
Climatic Evidence
 Geologists discovered layers
of debris from ancient glaciers in
Southern Africa and South America
 Areas today are to warm for glaciers
Missing Mechanisms
 Idea strongly opposed and rejected
 Continents plowed through ocean floor
 Easily disproved by geologic evidence
Mid-Ocean Ridges
1947 scientists set out to
map Mid-Atlantic Ridge
Findings
 Rocks closer to the ridge
 are younger than rocks
farther from the ridge
 Ocean floor is very young
175 million years
 Rocks on land 3.8 billion
Sea-Floor Spreading
H.H. Hess-
proposed sea-floor spreading
 Center of a ridge has a crack or rift in Earth’s crust
Sea Floor Formation
1. Earth rises to fill crack
2. As ocean floor moves outward
3. Magma cools and solidifies
Hypothesis- Wegener's missing mechanism
If the ocean floor was moving, so were the continents?
Paleomagnetism
Earth’s magnetic field not always pointed north
Magnetic Reversals
magnetic field north= normal polarity
Magnetic field south= reversed polarity
Pattern alternating normal/reversed
Geomagnetic Reversal Time Scale
Magnetic Symmetry
Match magnetic patterns on each side of mid-ocean ridge- rock
ages could be assigned
Wegener Redeemed
Magnetic patterns show changes over
time
Sea-floor spreading provided a way for
continents to move over Earth’s surface
Became accepted in scientific community
Mechanism that verified Wegener’s
hypothesis
Section 2
Objectives
Summarize the theory of plate tectonics.
Identify and describe the three types of plate
boundaries.
List and describe three causes of plate
movement.
How Continents Move
Continents and Oceans are carried along
moving tectonic plates
Lithosphere
 Upper part of mantle
 Broken into tectonic plates which ride
asthenosphere
Asthenosphere
 Plastic rock
Earth’s Crust
 Oceanic and Continental
Tectonic Plates
Scientist Identify
 15 major tectonic plates
 By way of Earthquakes and Volcanoes
Three Types of Plate Boundaries
1. Divergent
2. Convergent
3. Transform
Divergent Boundaries
Two plates move away from each other
Commonly found on ocean floor
Magma rises as plates move apart forming
new lithosphere Mid-ocean ridges
Convergent Boundaries
Two plates collide with one another
1. Continental-Oceanic= subduction
2. Continental-Continental= uplift
3. Oceanic-Oceanic= deep-ocean
trench/island arc
Transform Boundaries
Two plates slide past one another
Scrape and cause stress= earthquake
No magma is produced
San Andreas fault
Causes of Plate Motion
Mantle Convection
Hot material rises- cooler denser material
flows away
Causes of Plate Motion
Ridge Push
Cooling rock sinks forcing plate away from
mid-ocean ridge
Causes of Plate Motion
Slab Pull
Plates pull away from each other at midocean ridges
Section 3
Objectives
Identify how movements of tectonic plates
change Earth’s surface.
Summarize how movements of tectonic plates
have influenced climates and life on Earth.
Describe the supercontinent cycle.
Pyramid
1. Place sheet of paper in front of you. Fold lower left
corner of the paper diagonally to the opposite edge of
the paper.
2. Cut off the tab of paper created by the fold.
3. Open paper so that it is a square. Fold lower right
corner of the paper diagonally to the opposite corner to
form a triangle.
4. Open the paper. The creases of the two folds will have
created an X.
5. Using, scissors, cut along one of the creases. Start fron
any corner, and stop at the center point to create two
flaps. Attach one of the flaps on the other.
Reshaping The Earth’s Crust
Side 1
Define rifting
How does the Earth’s crust break/crack?
Define terrane.
List 3 characteristics of terranes
Where do terranes become part of the
continent?
Effects of Continental Change
Side 2
What effects a continents climate?
What Geologic evidence supports
changes in climate?
How are species/populations affected from
continetal rifting or the formations of
mountains?
Supercontinent Cycle
Side 3
Why supercontinents form?
Formation of Pangaea- time/mountain
ranges
Breakup of Pangaea
The Modern Continents
On the bottom of your pyramid list
three changes in geography that are
likely to happen in the future
Reshaping Earth’s Crust
Rifting
Process by which a continent breaks apart
Terranes and Continental
Growth
Terrane- unique geologic history
Contains rock and fossils
Major fault boundaries
Properties do not match neighbors
Small volcanic islands, sea-mounts, atolls
Effects of Continental Change
Changes in Climate
Ice covered most of Earth’s surface- even
the Sahara
Ice sheet formed when continents were
close
Global temperatures changed as continents
drift
Changes in Life
Effects of Continental Change
Changes in Life
As continents rift mountains form, organisms
are separated
New species evolve
The Supercontinent Cycle
Geography of the Future