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Changes in Earth’s Surface

Vocabulary

For two-column notes, underlines titles are main ideas

Scientific Theory of Plate Tectonics

• Based on– Wegener’s Hypothesis

• Continents drifted to their current locations• South America and Africa were once in contact

– Sea-floor spreading• New lithosphere being created at mid-ocean ridge

• Rocks are newer closer to boundary

• Pattern of magnetic reversal mirrored on both side of boundary

• Pangaea– The original multi-continent

Changes in Earth’s Surface

Scientific Theory of Plate Tectonics• Evidence

• Similar fossils are found on both sides of the Atlantic where continents were once joined

• Similar rocks are found on both sides of the Atlantic where continents were once joined

• Glacial deposits found in Africa

• Tropical plant fossils found in Antarctica

Changes in Earth’s Surface

Scientific Theory of Plate Tectonics

• The theory of Plate tectonics was proposed in 1960s based on the theory of continental drift.– It explains the formation and deformation of the

Earth’s surface.

• Continents are carried along on huge slabs (plates) on the Earth’s outermost layer (Lithosphere).

• Earth’s outermost layer is divided into 12 major Tectonic Plates (~80 km deep). These plates move a few centimeters per year.

Mantle Convection

• Scientific Theory of Plate Tectonics– Causes of Plate Motion

• Mantle Convection

Draw this. Be sure to label the boundaries and convection cells

LOCATION OF TECTONIC PLATES

Divergent plate boundariesDivergent plate boundaries: where plates : where plates move apart (separating plates)move apart (separating plates)

Convergent Plate boundariesConvergent Plate boundaries: where : where plates come together (colliding plates)plates come together (colliding plates)

Transform plate boundariesTransform plate boundaries: where plates : where plates slide past each other (sliding plates)slide past each other (sliding plates)

Types of plate boundaries

Divergent (Tension)Divergent (Tension)

Convergent (Compression)Convergent (Compression)

Transform (shearing)Transform (shearing)

Types of plate boundaries

Draw a picture of each

Types of plate boundaries

Types of Plate BoundariesDivergent• Plates move away from

each other (tension)• New lithosphere is formed

(we know because the rocks at the boundary are younger than rocks further away)

• A divergent boundary in the ocean produces mid-ocean ridges.

• A divergent boundary on land produces rift valleys.

Types of Plate BoundariesDivergent • As magma cools to form new lithosphere, rocks

containing iron are magnetized in the same direction as Earth’s magnetic field.– When the Earth’s magnetic field reverses every 70,000

years, alternate patterns of magnetism are formed.

– These patterns mirror each other across the mid-ocean ridge

Alternating Magnetic Bands Found in the Ocean

Types of Plate Boundaries

Divergent: ocean-ocean

Types of Plate Boundaries

Convergent• Plates move toward each other (compression)• Lithosphere is consumed (forced down into the

mantle)• Oceanic plates are more dense than continental plates• There are three types of convergent plate boundaries

– Oceanic-continental plate– Oceanic-oceanic plate– Continental-continental plate

• Oceanic-continental plates collide

• Oceanic plate subducts below continental

• Forms a subduction zone

• Earthquakes and volcanoes

Types of Plate Boundaries

Convergent: ocean-continental

Types of Plate Boundaries

Convergent: ocean-continental

Types of Plate Boundaries

• 2 oceanic plates collide

• One plate dives (subducts) beneath other

• Forms subduction zone

• Earthquakes and volcanoes

• Forms chain of islands called an island arc

• Also forms ocean trench

Convergent: oceanic-oceanic

Types of Plate Boundaries

• 2 continental plates collide

• Neither plate wants to subduct

• Collision zone forms high mountains

• Earthquakes, no volcanoes

example: Himalayasexample: Himalayas

Convergent: continental-continental

Types of Plate Boundaries

Convergent: continental-continental

• Two plates slide past each other• Lithosphere is neither consumed nor destroyed.• Responsible for most of the earthquakes• Usually occur in oceans but the most famous are

on land (like San Andreas Fault)

Types of Plate BoundariesTransform

Transform Plate Boundary 3Types of Plate BoundariesTransform

What drives plate movement?

• Ultimately: heat transported from core and mantle to surface

• Heat transported by convection

• Core is ~5,000°C and surface is ~0°C

• Where mantle rises: rifting

• Where mantle sinks: subduction zones

Plate tectonics affect climate

• Antarctica was once tropical (fossils of palm trees) but drifted to its current location at the South Pole (frozen)

• Distance between continents affect ocean currents, which affect climate

Classwork 1

1. What causes tectonic plate movement?2. Name one way in which we know that the seafloor in

the divergent boundary (spreading plates) in the mid-Atlantic Ocean is creating new ground.

3. ____ boundaries are most often associated with earthquakes

4. This often occurs where oceanic and continental plates meet at a convergent boundary

5. This often occurs where continental plates meet each other at a convergent boundary

6. This often occurs when oceanic plates meet each other at a convergent boundary

Copy the questions into your notebook (right-side) and answer them

Classwork 1

7. A chain of islands called an ___ ___ may be formed where oceanic plates converge

Copy the questions into your notebook (right-side) and answer them