Ch 9 Notes

Ch 9 NotesMr. Russo

Beaumont High School

Divergent boundary Convergent boundary Transform fault

boundary Oceanic Ridge Rift Valley Seafloor Spreading

Subduction Zone Trench Continental Volcanic

Arc Volcanic Island Arc Paleomagnetism Hot Spot

Ch 9 Vocab Matrix (Pg 45)

We will be able to describe the 4 pieces of evidence for the theory of continental drift.

Objective: Ch 9.1 Pg 47

Continental Drift – The continents had once been joined to form a single supercontinent◦Proposed by Alfred Wegner

Continental Drift

Pangaea – The supercontinent (All Land)◦Continents broke apart and drifted to their current position

Pangaea

Continental Puzzle – Continents appear to form a puzzle that can be put together

What evidence supports continental Drift?

Matching Fossils – Several of the same types of fossils on different landmasses

What evidence supports continental Drift?

Rock Types and Structures – Mountain belts that end on one coastline seem to reappear on a landmass across the ocean

What evidence supports continental Drift?

Ancient Climates – Found evidence of glacial ice in countries that shouldn’t have any glaciers

What evidence supports continental Drift?

Objective

The upper mantle and the crust act like a strong rigid layer. ◦This layer is called the lithosphere

Ch 9.2What is the theory of plate tectonics?

The lithosphere lies on top of the weaker mantle called the ASTHENOSPHERE

Plate – Plates are sections of the lithosphere◦7 Major plates◦Largest – Pacific Plate

◦Plates move 5cm/yr

Plates

Convergent

Divergent

Transform

What are the 3 types of plate boundaries?

Divergent Boundary – Occur when two plates move apart

Example – East African Rift Valley

Divergent Boundary

Example – East African Rift Valley

Convergent boundary – Occur when two plates move together

Convergent Boundary

Transform Boundary – When two plates grind past each other◦Example – San Andreas

Transform Boundary

Every Plate contains all 3 types of boundaries

Oceanic Ridge – Elevated area in the ocean, found along divergent boundaries

Ch 9.3Oceanic Ridge

Rift Valley – Deep faults found along divergent boundaries

Rift Valley

Seafloor Spreading – The process by which plate tectonics produce new lithosphere

Oldest part of the ocean floor is 180 million years old.

Seafloor Spreading

Subduction Zone – When one plate is forced down beneath another plate. (Convergent Boundary)

Subduction Zone

Trench – Surface Feature produced during a subduction zone.

Trench

Continental Volcanic Arc – When a continental and ocean plate collide, they produce volcanoes on the land.

Continental Volcanic Arc

Volcanic Island Arc – When 2 ocean plates collide, they produce volcanoes in the middle of an ocean, forming islands

Volcanic Island Arc

Mountains are formed when two continent plates collide.

Example – Himalayas in South Asia

Mountains

Transform Fault – Earthquakes – At Transform faults, plates grind past without destroying the lithosphere and produce earthquakes.

Example – San Andreas Fault , CA

Transform Fault - Earthquakes

Convergent Boundaries – Lithosphere is destroyed

Divergent Boundaries – Lithosphere is created

Transform Boundaries– Lithosphere is neither created nor destroyed.

Notice

Paleomagnetism – Study of changes in Earth’s magnetic field

Ch 9.4Paleomagnetism

Normal Polarity – Same magnetism as present day magnetic field

Normal Polarity

Reverse Polarity – Rocks that show opposite magnetism then present day

Reverse Polarity

The discovery of strips of rocks of alternating polarity across the ocean ridges.

What evidence supports theory of plate tectonics?

The youngest crust (Seafloor) is at the ridge crest, the oldest crust is further away

How old is the seafloor?

OldestYoungest

Hot Spot – A rising plume of mantle that creates a volcanic area (Hawaii)

Hot spot supports idea that the plates move over Earth’s surface

Hot spot

Shaded Region – Reverse Polarity

White Region – Normal Polarity