Transcript plates - pribaudo

Follow the key below to
positively participate in class
today:
• All information in () is the instructor
“speaking” to you – this does not need to
be written down.
• All information in LIME GREEN – main
ideas – should be written to the LEFT of
your divided page notes
• All information in YELLOW – details –
should be written to the RIGHT of your
divided page notes
Setting up your notes
• 1 (Get a lined piece of paper)
• 2 (Fold the left side 1/3 of the way in to
create a column to the left.)
• 3 (Put the heading at the very top – NAME
-DATE -BLOCK)
• 4 (Title your notes “Plate Tectonics”)
• 5 – REMEMBER:
• LIME GREEN – LEFT
• YELLOW - RIGHT
Looking at the world map, what do you notice
about the shape of the continents?
Jot down your ideas on your paper…
Layers Review
 The lithosphere is divided
into a number of large and
small plates and the
plates are floating on the
asthenosphere
Lithosphere = the Earth’s crust plus
the upper portion of the mantle layer
Alfred Wegener
• Early 1900’s - German scientist –
expertise in weather/climate
• Theorized that continents shift and slowly
move over long periods of time
• Coined the term, Pangaea
• Theory NOT accepted during his lifetime –
could not prove how they moved (missing
link)
Small error in Wegener’s theory
• NOT the continents that are drifting, it’s
the PLATES
• PLATES are composed of both oceanic
and continental crust
• FAULTS – the cracks between each plate
(Notice the plates contain
oceanic and continental crust)
Plate motion based on The Global Positioning System (GPS)
Evidence of Continental Drift
Theory
(Write these four topics with THREE
SPACES in between)
1. Fossils
2. Landforms
3 .Climate
4. Puzzle fit
(Now, with your buddy, DESCRIBE these
four topics on the right side.)
Evidence
o Minerals,
fossils, and
mountains
on now
different
continents
match if
the
continents
were
together
The Mystery of Brachiosaurus (~3 min)
Evidence
o Glaciation patterns indicate a common
ice cap at the South Pole
o Pangaea began to split apart 200
million years ago
o Diagram
Laurasia
Pangaea
Gondwanaland
North America
Greenland
Eurasia
West G.
East G.
Africa
S.America
Antarctica
Australia
India
5. Seafloor spreading
• Mid-ocean ridge – underwater mountain
chains that run through all of Earth’s
ocean basins
• Oldest crust near the borders, newest
crust in the center
• New ocean floor crust is
being created at the midocean ridges
Speed of Spreading

Atlantic Ocean –
2-3 cm/year

South Pacific
Ocean – 15-18
cm/year
What evidence do we have to support this idea
of seafloor spreading?
o Midocean ridges are warmer than
surrounding ocean floors
o Active volcanoes on ridges, earthquakes
on ridges
o Midocean ridge rocks are younger than
surrounding ocean floor rocks
o Midocean ridge volcanoes are younger
than volcanoes further away
6. Magnetic Reversals
• most important evidence for seafloor
spreading is recorded magnetic reversals
in the ocean floor
• magnetic minerals in molten rock provide
clues to the magnetic reversal of the poles
• final, concrete proof that the seafloor is
spreading AND plates are drifting
Polar Reversal Magnetism
Magnetic Poles
Magnetic Field Reversals—2:54
HOW do the plates
move?
Convection Currents
• Hot magma in the Earth
moves toward the surface,
cools, then sinks again.
• Creates convection currents
beneath the plates that cause
the plates to move.
Heat Transfer
Three Main Types:
Conduction
Radiation
Convection
Conduction
• Transfer of heat by direct contact
• Conductors – the better the conductor the
faster the heat transfer
• Ex)
• egg frying in the pan
• Hand on the fire
Radiation
• Heat transfer through empty space
• Ex) sun – common source of heat
Convection
• Heat transfer through the movement of
“fluids”
• ex)boiling water, earth’s asthenosphere
Plate Boundaries
Divergent boundary:
Divergent Boundaries
• Boundary between two plates
that are moving apart or rifting

• RIFTING causes SEAFLOOR
SPREADING
Plate Boundaries
Divergent boundary:
o Plates are moving away
from each other
o Midocean ridges are
created and new ocean
floor plates are created
Features of Divergent
Boundaries
• Mid-ocean ridges
• rift valleys – Great Rift Valley,
East Africa
• fissure volcanoes
Leif the Lucky Bridge Bridge between continents in Reykjanes
peninsula, southwest Iceland across the Alfagja rift valley, the
boundary of the Eurasian and North American continental tectonic
plates.
Transform Fault Boundary
 Plates are neither moving
toward nor away from each
other, they are moving past
one another.
Transform Fault Boundary
 The plates may move in opposite
directions or in the same
directions but at different rates
and frequent earthquakes are
created (example: San Andreas
Fault)
Transform Fault Boundaries
• Boundary between two plates
that are sliding past each other
• EARTHQUAKES along faults
San Andreas Fault
San Andreas Fault, CA
 Convergent Boundary:
plates are moving toward
each other and are
colliding (3 types)
Convergent Boundaries
• Boundaries between two
plates that are colliding
 
• There are 3 types…
Type 1
• Ocean plate colliding with a
less dense continental plate
• Subduction Zone: where the
less dense plate slides over
the more dense plate
• VOLCANOES occur at
subduction zones
Andes Mountains,
South America
When Ocean Plates collide with Contintental Plates
• Create subduction zones,
trenches
• Create near coast volcanoes
• Benioff shear zones (a
pattern of earthquakes as an
ocean plate grinds down the
underneath side of a continent)
Benioff Shear Zones
Type 2
• Ocean plate colliding with
another ocean plate
• The less dense plate slides
over the more dense plate
creating a subduction zone
called a TRENCH
Aleutian Islands, Alaska
When ocean plates collide with other ocean plates
Island arcs are created
(a pattern of volcanic islands created
from a subduction zone that is
located off the coast)
Type 3
• A continental plate colliding
with another continental plate
• Have Collision Zones:
–a place where folded and thrust
faulted mountains form.
When a continental plate collides with another
continental plate
• Mountain ranges are
created
• (example: Himalayan
Mountains)
Himalayan Mountains
Mountains 2:46
So is the
Earth
getting
bigger?
So is the Earth getting bigger?
o No
o Plates are destroyed as fast as they
are created (2 ways)
o Plates may be subducted and melted
or may be pushed upward to form
mountains
What causes this?
Convection currents within the mantle

The up-welling leg of the current creates
a divergent boundary which produces
midocean ridges

The down-welling leg of the current
creates one type of convergent boundary
that results in trenches and a subduction
zone