Download Plate Tectonics

Do Now:

We all know that wood floats on
water. Yet, the wood is not stationary.
What drives the movement of the
wood on the water?
Aim: How do continents
move?
Continental Drift
_________
Wegener
proposed the
theory that the
crustal plates are
moving over the
mantle. This was
supported by
fossil and rock
type evidence;
also matching of
coastline shapes.
lithosphere
asthenosphere
mesosphere
Lithosphere (hard)
Asthenosphere (soft)
Mesosphere
Earth formed 4.6 bya
Inner Core- 4300oC
• mostly iron core
• inner part is so compressed that it is solid
Outer Core- 3700oC
• iron and sulfur
• liquid
Mantle- 1000oC
mesosphere
•Solid
•~ 2300 km thick
asthenosphere
• Soft
•~3000 km thick
lithosphere
•hard
•~100 km thick
Crust
• floats on top of lithosphere
continental crust (granite)
•20 to 70 km thick
oceanic crust (basalt)
• ~ 8 km thick
Hess- Convection Cell Theory
Convection Currents
The force responsible for plate movement is __________.
Evidence for plate tectonics
• Pattern of worldwide earthquakes (left)
matches plate boundaries (right)
The 3 types of plate
boundaries
1.
Divergent
2.
Convergent
3.
Transform
Plate Boundaries
The following two slides show maps of
the current major plate boundaries
and their relative motions.
 You should be able to describe
various landforms created by different
plate movements.

Plate Boundaries
apart
Divergent Boundary – moving _____
 Convergent Boundary – moving
________
together
 Transform Fault Boundary – moving
sideways past each other
________________________

Divergent plate boundaries

The MidAtlantic Ridge
is a divergent
plate boundary
where sea floor
spreading
occurs
Divergent plate boundaries

Iceland sits
atop a
divergent plate
boundary
where
continental
rifting occurs
Divergent plate boundaries

Formation
of an
ocean
basin by
rifting and
sea floor
spreading
Divergent boundary of two continental plates.
rift valley
East African Rift
Creates a __________.
Example: _____________
Convergent plate boundaries
a. Ocean-continent

Convergent
plate
boundaries
vary
depending
on the type
of crust
c. Continentcontinent
b. Ocean-ocean
Convergent plate boundaries

An oceancontinent
convergent plate
boundary
produces the
Cascadia
subduction zone
and Cascade
Mountains
Convergent plate
boundaries

A continentcontinent
convergent
plate boundary
produces the
Himalaya
Mountains
Convergent boundary of two oceanic plates.
island arc and a _____.
trench Example: _____
Japan
Creates an ________
Convergent boundary of an oceanic plate and a
continental plate. Forms a _______
volcanic mountain range
trench Examples: Cascades
Andes Mts
and a ______.
_______ or _______
Convergent boundary of two continental plates. Forms
Himalayas
a ______
folded mountain range. Examples: ___________,
Appalachians
Alps, ______________
Transform plate boundaries


Transform plate
boundaries
occur between
segments of the
mid-ocean ridge
Can also occur
on land (ex: San
Andreas Fault)
Transform-fault boundary where the North American
and Pacific plates are moving ____
past each other.
San Andreas Fault in California
Example: ________________
Plate Boundaries Review





Places where plates move apart are called
_____________
boundaries.
divergent
When continental plates diverge a
rift valley
___________
is formed.
When two oceanic plates converge what is
an island arc and a trench
created? _________________
The Appalachians formed mainly from
continental plate collisions and therefore are a
__________
mountain range.
folded
Convection currents
The force moving the plates is ____________
.
Inquiry
1. What layer of the mantle do the plates
move on?
2. What is the convection cell theory?
3. Wegeners evidence for continental drift
includes: ______.
4. Why was his theory disregarded?
5. What did Marie Tharp discover?
6. How are trenches formed?