Transcript The Theory of Plate Tectonics • What is the theory of plate tectonics? • What are the three types of plate boundaries? • Why.

The Theory of Plate Tectonics
• What is the theory of plate tectonics?
• What are the three types of plate
boundaries?
• Why do tectonic plates move?
•Lesson 3 Reading Guide - Vocab
The Theory of Plate Tectonics
• plate tectonics
• subduction
• lithosphere
• convection
• divergent plate boundary
• ridge push
• transform plate boundary
• slab pull
• convergent plate boundary
The Plate Tectonics Theory (cont.)
What is plate tectonics?
The Plate Tectonics Theory
• The
theory of plate tectonics, proposed in
the late 1960s, states that Earth’s
surface is made of rigid slabs of rock, or
plates, that move with respect to each
other.
• Plate tectonics suggests that Earth’s
surface is divided into large plates of rigid
rock and each plate moves over Earth’s
hot and semiplastic mantle.
The Plate Tectonics Theory (cont.)
• Geologists
use the word tectonic to
describe the forces that shape Earth’s
surface and the rock structures that form
as a result.
• The cold and rigid outermost rock layer of
the Earth is called the lithosphere.
• The lithosphere is made up of the crust
and the solid, uppermost mantle.
The Plate Tectonics Theory (cont.)
• The
lithosphere is thin below mid-ocean
ridges and thick below continents.
• Earth’s tectonic plates are large pieces of
the lithosphere that fit together like the
pieces of a giant jigsaw puzzle.
• The layer of Earth below the lithosphere,
called the asthenosphere, is so hot that it
behaves like a plastic material and enables
Earth’s plates to move.
Earth’s Tectonic Plates
•Continental Drift Movie Activity
•
Read HANDOUT
Plate Boundaries (cont.)
What are the three types of
plate boundaries?
Plate Boundaries
A divergent plate boundary forms where two
plates separate.
• When the seafloor spreads at a mid-ocean
ridge, lava erupts, cools, and forms new oceanic
crust.
• Divergent plate boundaries can also exist in the
middle of a continent, where they pull
continents apart and form rift valleys.
•
•Lesson 3-3
Plate Boundaries (cont.)
A transform plate boundary forms where two
plates slide past each other.
• As they move past one another, the plates can
get stuck and stop moving.
• Stress builds up where the plates are stuck until
they eventually break and suddenly move apart,
resulting in a rapid release of energy as
earthquakes.
•
•Lesson 3-3
Plate Boundaries (cont.)
Convergent plate boundaries form where two
plates collide.
• The denser plate sinks below the more buoyant
plate in a process called subduction.
• The area where a denser plate descends into
Earth along a convergent plate boundary is
called a subduction zone.
•
Plate Boundaries (cont.)
subduction
from Latin subductus, means “to lead under, removal”
Plate Boundaries (cont.)
•
When an oceanic plate and a continental plate
collide, the denser oceanic plate subducts under
the edge of the continent, creating a deep ocean
trench and a line of volcanoes above the
subducting plate on the edge of the continent.
•Lesson 3-3
Plate Boundaries (cont.)
•
When two continental plates collide, neither plate
is subducted, and mountains form from uplifted
rock.
•Lesson 3-3
•Creating the 3 plate boundaries
•
Foldables Activity
Evidence for Plate Tectonics
Scientists can measure how fast continents
move using a network of satellites called the
Global Positioning System.
• Because plates are rigid, tectonic activity occurs
where plates meet.
•
Evidence for Plate Tectonics (cont.)
How are earthquakes and
volcanoes related to the theory
of plate tectonics?
Evidence for Plate Tectonics (cont.)
Volcanoes form where plates separate along a
mid-ocean ridge or continental rift or collide
along a subduction zone.
• Mountains can form where two continents
collide.
•
Notice the relationship between earthquake
epicenters, volcanoes, and plate boundaries.
Plate Motion (cont.)
What causes convection?
Plate Motion
Earth’s plates move because the asthenosphere
moves underneath the lithosphere.
• Convection is the circulation of material caused by
differences in density.
• Hot mantle material rises upward and comes in
contact with Earth’s crust.
•
Plate Motion (cont.)
As the mantle cools, it becomes denser and
then sinks, forming a convection current.
• Convection currents in the asthenosphere act
like a conveyor belt moving the lithosphere
above it.
• There are three forces that interact to cause
plate motion: basal drag, ridge push, and slab
pull.
•
Plate Motion (cont.)
Basal drag refers to how convection currents in
the asthenosphere circulate and drag the
lithosphere like a conveyor belt.
• Rising mantle material at mid-ocean ridges
creates the potential for plates to move away
from the ridge with a force called ridge push.
•
•Lesson 3-4
As a slab, or dense plate, sinks, it pulls on the
rest of the plate with a force called slab pull.
A Theory in Progress
Plate tectonics has become the unifying theory
of geology, but several unanswered questions
remain.
• Why is Earth the only planet in the solar system
that has plate tectonic activity?
• Why do some earthquakes and volcanoes occur
far away from plate boundaries?
•
• What forces dominate plate motion?
• What will scientists study next? This is
a 3-D image
of seismic
wave
velocities
from
a new
technique
called
anisotropy.
•Lesson 3 - VS
• Tectonic plates are
made of cold and
rigid slabs of rock.
• Mantle convection—
the circulation of
mantle material due to density
differences—drives plate motion.
•Lesson 3 - VS
• The three types of plate boundaries
are divergent, convergent, and
transform boundaries.
•Lesson 3 – LR1
What word do geologists use to describe the forces that shape
Earth’s surface?
A. semiplastic
B. lithosphere
C. tectonic
D. mantle
•Lesson 3 – LR2
Which of these is made up of the crust and the solid, uppermost
mantle?
A. seafloor
B. lithosphere
C. biosphere
D. hydrosphere
•Lesson 3 – LR3
What type of boundary forms where two plates separate?
A. convergent plate boundary
B. transform plate boundary
C. new plate boundary
D. divergent plate boundary
•Lesson 3 - Now
Do you agree or disagree?
5. Continents drift across a molten
mantle.
6. Mountain ranges can form when
continents collide.
•Chapter Review Menu
Key Concept Summary
Interactive Concept Map
Chapter Review
Standardized Test Practice
•The BIG Idea
The theory of plate tectonics
states that Earth’s
lithosphere is broken up into
rigid plates that move over
Earth’s surface.
•Key Concepts
1
The Continental
Drift Hypothesis
Lesson 1:
•
•
The puzzle piece fit of
continents, fossil evidence,
climate, rocks, and mountain
ranges supports the hypothesis
of continental drift.
Scientists were skeptical of
continental drift because
Wegener could not explain the
mechanism for movement.
•Key Concepts 2
Lesson 2: Development of a Theory
•
•
•
Seafloor spreading provides a mechanism for
continental drift.
Seafloor spreading occurs at mid-ocean ridges.
Evidence of magnetic reversal in rock, thermal energy
trends, and
the discovery of
seafloor spreading
all contributed to
the development
of the theory of
plate tectonics.
•Key Concepts
3 of Plate Tectonics
The Theory
Lesson 3:
•
•
Types of plate boundaries, the location of earthquakes,
volcanoes, and mountain ranges, and satellite
measurement of plate motion support the theory of
plate tectonics.
Mantle convection, ridge
push, and slab pull are
the forces that cause
plate motion. Radioactivity
in the mantle and thermal
energy from the core
produce the energy for
convection.
•Chapter Review – MC1
Which of these have been found on
several continents separated by oceans,
suggesting that they were once
geographically closer together?
A.
B.
C.
D.
animals
ice sheets
plant fossils
plate boundaries
•Chapter Review – MC2
Which of these refers to the process by
which new oceanic crust forms along a midocean ridge as older oceanic crust moves
away from the ridge?
A.
B.
C.
D.
continental drift
plate tectonics
seafloor spreading
magnetic reversal
•Chapter Review – MC3
What is the rigid outermost layer of Earth called?
A.
B.
C.
D.
mantle
lithosphere
plate
transform plate boundary
•Chapter Review – MC4
What forms where two plates slide past each other?
A.
B.
C.
D.
transform plate boundary
divergent plate boundary
convergent plate boundary
semiplastic mantle
•Chapter Review – MC5
What is the process in which a denser plate sinks below a more
buoyant plate?
A.
B.
C.
D.
seafloor spreading
convergence
convection
subduction
•Chapter Review – STP1
What is the name of the supercontinent that all continents were
once part of?
A.
B.
C.
D.
Wegener
Pangaea
mantle
seafloor
•Chapter Review – STP2
Where did scientists find glacial features that are usually associated
with cooler climates?
A.
B.
C.
D.
Antarctica
plate boundaries
mountain ranges
Africa
•Chapter Review – STP3
Which term refers to vast mountain ranges on the seafloor?
A.
B.
C.
D.
volcanoes
oceanic crust
pillow lava
mid-ocean ridges
•Chapter Review – STP4
Which of these states that Earth’s surface is
made of rigid slabs of rock that move with
respect to one another?
A. the theory of plate tectonics
B. the theory of mid-ocean ridges
C. the theory of divergent plate
boundaries
D. the theory of transform plate
boundaries
•Chapter Review – STP5
What is the name for the force that pulls on the rest of a plate as
part of a dense plate sinks?
A.
B.
C.
D.
ridge push
basal drag
slab pull
plate tectonics