Follow the key below to Follow the key below to positively participate in class positively participate in class

today: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 notesSetting 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, Looking at the world map, what do you notice about the what do you notice about the

shape of the continents?shape of the continents?

Jot down your ideas on your paper…

The lithosphere is divided into a number of large and small plates and the plates are floating on the asthenosphere

Layers ReviewLayers Review

Lithosphere = the Earth’s crustcrust plus the upper portion of the mantlemantle layer

Alfred WegenerAlfred 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 theorySmall 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 (Notice the plates contain oceanic and continental crust)oceanic and continental crust)

Plate motion based on The Global Positioning System (GPS)

Evidence of Continental Drift Evidence of Continental Drift TheoryTheory

(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.)

o Minerals, fossils, and mountains on now different continents match if the continents were together

EvidenceEvidence

The Mystery of Brachiosaurus (~3 min)

o Glaciation patterns indicate a common ice cap at the South Pole

EvidenceEvidence

o Pangaea began to split apart 200 million years ago

o DiagramNorth America

Laurasia GreenlandEurasia

PangaeaAfricaWest G. S.America

GondwanalandAntarctica

East G. AustraliaIndia

5. Seafloor spreading5. 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 mid-ocean ridges

Atlantic Ocean – 2-3 2-3 cm/year

South Pacific Ocean – 7-97-9 cm/year

Speed of SpreadingSpeed of 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

What evidence do we have What evidence do we have to support this idea of to support this idea of

seafloor spreading?seafloor spreading?

6. Magnetic Reversals6. 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 MagnetismPolar Reversal Magnetism

Magnetic Poles Magnetic Field Reversals—2:54

HOW do the plates move?

Convection CurrentsConvection 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 TransferHeat Transfer

Three Main Types:

Conduction

Radiation

Convection

Conduction 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

RadiationRadiation

• Heat transfer through empty space

• Ex) sun – common source of heat

ConvectionConvection

• Heat transfer through the movement of “fluids” – can be liquid or gas

• ex)boiling water, earth’s asthenosphere

Plate Plate BoundariesBoundaries

Divergent boundary: Divergent boundary:

Divergent BoundariesDivergent Boundaries

• Boundary between two plates that are moving apart or rifting

• RIFTING causes SEAFLOOR

SPREADING

Plate BoundariesPlate Boundaries

Divergent boundary: Divergent boundary: o Plates are moving away

from each othero Midocean ridges are

created and new ocean floor plates are created

Features of Divergent Features of Divergent BoundariesBoundaries

• 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 BoundaryTransform Fault Boundary

Plates are neither moving toward nor away from each other, they are moving past one another.

Transform Fault BoundaryTransform 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 BoundariesTransform Fault Boundaries

• Boundary between two plates that are sliding past each other

• EARTHQUAKES along faults

San Andreas FaultSan Andreas Fault

San Andreas Fault, CASan Andreas Fault, CA

Convergent BoundaryConvergent Boundary: plates are moving toward each other and are colliding (3 types)

Convergent BoundariesConvergent Boundaries

• Boundaries between two plates that are colliding

• There are 3 types…

Type 1Type 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, Andes Mountains, South AmericaSouth America

• 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)

When Ocean Plates collide with When Ocean Plates collide with Contintental PlatesContintental Plates

Benioff Shear ZonesBenioff Shear Zones

Type 2Type 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, AlaskaAleutian Islands, Alaska

When ocean plates collide with When ocean plates collide with other ocean platesother ocean plates

Island arcs are created (a pattern of volcanic islands

created from a subduction zone that is located off the coast)

Type 3Type 3

• A continental plate colliding with another continental plate

• Have Collision Zones:–a place where folded and thrust

faulted mountains form.

• MountainMountain rangesranges are created

• (example: Himalayan Mountains)

When a continental plate collides When a continental plate collides with another continental platewith another continental plate

Himalayan MountainsHimalayan Mountains

Mountains 2:46

So is the Earth getting bigger?

o Noo 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

So is the Earth getting bigger?So is the Earth getting bigger?

Convection currents within the mantle

The up-welling leg of the current creates a divergent boundary which produces midocean ridges

What causes this?What causes this?

The down-welling leg of the current creates one type of convergent boundary that results in trenches and a subduction zone