Plate TectonicsPlate Tectonics

Earth’s InteriorEarth’s Interior

Alfred Wegener (1880-1930)

Alfred Wegener (1880-1930)

German astronomer/meteorologist

Worked in Greenland on polar air circulation

Died on expedition in 1930Proposed Continental Drift in

1912

German astronomer/meteorologist

Worked in Greenland on polar air circulation

Died on expedition in 1930Proposed Continental Drift in

1912

Theory of Continental Drift

Theory of Continental Drift

-Earth’s continents had once been joined as a single landmass

-Earth’s continents had once been joined as a single landmass

• Pangaea “all lands”- Ancient landmass made up of all continents forming a supercontinent.

- Began to break apart about 200 million years ago (mya)

• Continental Drift

Pangaea Ultima?Pangaea Ultima?

Evidence from Rock Formations

Evidence from Rock Formations

Rock formations (ex. mountain ranges) fractured as the continents separated.

Same rocks are found in the Appalachians and also in Greenland and Europe.

Rock formations (ex. mountain ranges) fractured as the continents separated.

Same rocks are found in the Appalachians and also in Greenland and Europe.

Evidence from FossilsEvidence from Fossils

Wegener found similar fossils of different land animals and plants on separated continents.

Wegener found similar fossils of different land animals and plants on separated continents.

Ancient Climatic Evidence

Ancient Climatic Evidence

Sedimentary Rock CoalSedimentary Rock Coal• Coal forms from dead swamp plants.

• Coal was found in Antarctica, therefore Antarctica must have been closer to the equator at one time.

Ancient Climatic Evidence Cont.

Ancient Climatic Evidence Cont.

Glacial DepositsGlacial Deposits-290 mya glacial deposits found in Africa, India, Australia, and South America.

-These continents were once located on the South Pole.

Continental Drift was rejected.

Continental Drift was rejected.

People rejected the hypothesis because:

1- they believed continents and ocean basins were permanent, fixed features of Earth’s surface

2- Wegener could not explain what forces could cause a continent to move without shattering

People rejected the hypothesis because:

1- they believed continents and ocean basins were permanent, fixed features of Earth’s surface

2- Wegener could not explain what forces could cause a continent to move without shattering

Sea-Floor Spreading

Isochron MapIsochron Map a line map that connects points of the same age. Check this out on Google EARTH. a line map that connects points of the same age. Check this out on Google EARTH.

Theory of Plate Tectonics Evidence

Theory of Plate Tectonics Evidence

1. Rock Age • Young Rocks –near ocean ridges.• Older Rocks –near deep-sea trenches • Ridges –the age of the oceanic crust

increases with distance from a ridge.

• Seafloor Age – oldest part = 180 million years old. Oldest Continental crust = 3.8 billion years old.

1. Rock Age • Young Rocks –near ocean ridges.• Older Rocks –near deep-sea trenches • Ridges –the age of the oceanic crust

increases with distance from a ridge.

• Seafloor Age – oldest part = 180 million years old. Oldest Continental crust = 3.8 billion years old.

Earth’s Magnetic FieldEarth’s Magnetic FieldOur magnetic field is called the magnetosphere. It stretches out through the atmosphere and acts as a protective barrier to deadly, high-energy solar radiation.

Movement of the liquid outer core of the Earth generates a strong magnetic field that surrounds the planet. This causes the Earth to act much like a large magnet, with the poles of the magnet located near the poles of the Earth.

Theory of Plate Tectonics Evidence.

Theory of Plate Tectonics Evidence.

1960s Technology:1960s Technology:• Magnetometer –makes a map from detecting small changes in magnetic fields.

•Geologists mapped volcanoes and earthquakes along plate boundaries.

• Sonar – used to map out the seafloor

Theory of Plate Tectonics Evidence

Theory of Plate Tectonics Evidence

2. Paleomagnetism is the past formation of rocks containing iron-bearing minerals which provide a record of earth’s magnetic field.

Basaltic rocks are found in the ocean crust and are rich in iron and when they cool the iron-bearing minerals orient parallel to Earth’s magnetic field.

Lava

2. Paleomagnetism is the past formation of rocks containing iron-bearing minerals which provide a record of earth’s magnetic field.

Basaltic rocks are found in the ocean crust and are rich in iron and when they cool the iron-bearing minerals orient parallel to Earth’s magnetic field.

Lava

Magnetism & Paleomagnetism support sea-floor spreading and Theory of Plate Tectonics.

Geomagnetic Time Scale

Geomagnetic Time Scale

Magnetic Reversal

Normal Polarity

Reversed Polarity

Magnetic Reversal

Normal Polarity

Reversed Polarity

a change in Earth’s magnetic field.

a magnetic field that has the same orientation as Earth’s present field

a magnetic field that is opposite to the present field

Major plates of the world.

Major plates of the world.

Mid-ocean Ridge – crust is formed.

Mid-ocean Ridge – crust is formed.

Subduction Zone – crust is destroyed.Subduction Zone – crust is destroyed.

Slab-pull and Convection Currents cause plate

motion.

Slab-pull and Convection Currents cause plate

motion.

Plate BoundariesPlate Boundaries

Plate BoundariesThree Major Types

Plate BoundariesThree Major Types

1. Convergent

- places where tectonic plates interact with one another.

•plates come together.

2. Divergent

3. Transform

•plates move away from one another.

•plates move horizontally past one another

Divergent Boundary

Divergent - Iceland RiftDivergent - Iceland Rift

Convergent Oceanic- Continental Boundary

Oceanic-Continental Cascade Range

Oceanic-Continental Cascade Range

Convergent Oceanic-oceanic Boundary

Convergent Continent-Continent Boundary

Continental-Continental Himalayas

Continental-Continental Himalayas

Transform Boundary

Transform – San Andreas Fault

Transform – San Andreas Fault

Know this drawing!Know this drawing!