Layers of the Earth

Pre Ap - Notes: pg 113

Layers of the Earth

Layers of the EarthCrust •Crust: a layer of rock that forms

Earth’s outer skin–Includes land forms, soil, water, etc..

Layers of the EarthCrust •Basalt: Ocean crust made of dark

dense rock and is very thin•Granite: Continental crust that is less dense but is thicker (especially where mountains are)

Layers of the EarthMantle •Mantle: Layer of hot rock under the

crust•Lithosphere: upper most part of the mantle and the crust, solid

–About 100 kilometers thick

Layers of the EarthMantle •The temperature and pressure in the

mantle increases with depth•This pressure and high temperatures causes the lower part of the mantle to be soft and can flow easily, known as the asthenosphere•The mantle is 3,000 km thick

Layers of the EarthCore •Core: inner most part of the earth

consisting of 2 parts–Outer core: thick liquid of molten material–Inner core: dense ball of solid metal (iron and nickel)

Just the Facts

• The mantle makes up about 80% of the Earth’s total volume.

• Pressure at the center of the inner core may be more than 1 million times greater than air pressure at sea level.

• Crust material is 2.5-3.0 times denser than water, mantel material is 3.5-5.5 times denser than water, core material is 10-13 times denser than water

Fun Fact

• Suppose you could drive a car at 100km/hr (62 mi/hr) from Earth’s surface to the center of the core. At that speed the car would take about half an hour to drive through most continental crust, about another 29 hours to drive through the mantle, and about an additional 35 hours to drive to the center of the Earth.

Convection Currents and the Mantle

Convection Currents and the Mantle

Pre AP: Notes: Pg 114

Convection Currents and the MantleHeat Transfer

•Heat can transfer in 3 ways

1. Radiation1. Radiation

Transfer of heat energy by

electromagneticradiation

Example: waves onthe EMS scale

2. Conduction2. Conduction

Transfer of heatBy direct Contact

Example: touchinga metal spoon

In a pot of Boiling water

3. Convection3. Convection

Heat transferBy the movementOf heated liquids

And gasses

Example: Hot Air rises

Heat Transfer

Convection Currents and the MantleConvection Currents

•The difference between temperature and density of the fluid changes. This causes:

–Hot liquid to be less dense, moving it to the top–Cool liquid to be more dense, moving it to the bottom

Convection Currents and the MantleConvection Currents

Video

•The asthenosphere (middle mantle) is a soft liquid and experiences convection currents

–As the fluid close to the core heats, it rises to the top (near the lithosphere) and cools, causing it to cycle back down

Convection Currents and the MantleConvection Currents

•Convention currents in the mantle, cause the lithosphere (bottom of the crust) to move•This causes the crust of the earth to move around

Draw both pictures below in your notes

Heat rising

Coolnesssinking

Heat source

Heat Becomes

cool

Pg. 115 Draw both pictures below in your notes

Heat rising

Coolnesssinking

Heat source

Heat Becomes

cool

Drifting Continents

http://www.youtube.com/watch?v=_5q8hzF9VVE

Drifting ContinentsAlfred Wegener

•German scientist in early 1900s

Drifting ContinentsAlfred Wegener

•German scientist in early 1900s•His hypothesis stated that all the continents had once been joined together in a single land mass and have sense drifted apart

Drifting ContinentsAlfred Wegener

•German scientist in early 1900s•His hypothesis stated that all the continents had once been joined together in a single land mass and have sense drifted apart•He named the

mega continent

Pangea, which

means “all lands”

Drifting ContinentsAlfred Wegener

•Pangea existed over 300 million years ago•Pangea took tens of millions of years to move to where the continents are today

Drifting ContinentsContinental Drift and its evidence

•Continental Drift: Wegener’s idea that the continents slowly moved over Earth’s surfaces

Drifting ContinentsContinental Drift and its evidence

•Evidence from landforms: –Mountain range in Africa matches up with a mountain range in South America – European coal fields match up with North American coal fields

Drifting ContinentsContinental Drift and its evidence

•Evidence from Fossils–Fossils of the same animals (mesosaurus and lytrosaurus) have been found on different continents

•These reptiles once lived on a single land mass – Pangea

Drifting ContinentsContinental Drift and its evidence

•Evidence from Fossils–Glossopteris (fern like plant) fossils have been found in Africa, South America, Australia, India, and Antartica

Drifting ContinentsContinental Drift and its evidence

•Evidence from Climate–Evidence from fossils that the climate in South Africa was once much colder because there is evidence of glaciers

Where do you think South Africa was during Pangaea?

South Africa at the Pole

Drifting ContinentsContinental Drift and its evidence

•Evidence from Climate–Spitsbergen: island up by Norway which is covered in ice, but where fossils of tropical plants have been discovered

Where do you think Splisbergen was during Pangaea?

Drifting ContinentsContinental Drift and its evidence

Theory was not accepted by scientists…why?

Because Wegener could not identify the cause of continental drift

Sea Floor Spreading

In order to get sea floor spreading…

• We have to go back and remind ourselves about what convection currents are…

What are convection currents?

Heat rising

Coolnesssinking

Heat source

Heat Becomes

cool

The lithosphere is broken into different plates

Sea Floor SpreadingMid Ocean Ridge

•Mid Ocean Ridge: longest chain of mountains in the world under the oceans.

–Mountain range curves around the world like the seams on a baseball

Video: http://www.youtube.com/watch?v=sgDM6m0lUGY

Mid-Ocean Ridge

Sea Floor SpreadingMid Ocean Ridge

Video: Sonar video:

http://news.nationalgeographic.com/news/2011/04/110421-us-ocean-floor-mapping-vin-video/

•Sonar: device that bounces sound waves off under water objects to see their location and depth •Sonar mapped the mid ocean ridge

Sea Floor SpreadingHarry Hess •An American geologist who studied

mid-ocean ridges. •He suggested that the ocean floors move like conveyor belts, carrying the continents along with them.

–He came up with the idea of sea-floor spreading

Sea Floor Spreading

Sea Floor SpreadingSea Floor Spreading

1. At the mid-ocean ridge, molten material rises from the mantle and erupts.

2. Molten material then spreads out, pushing older rock away on both sides of the ridge

Sea Floor SpreadingSea Floor Spreading

3. As the molten material cools, it forms a strip of solid rock in the center of the ridge.

4. Eventually, more molten material will erupt and the cycle will begin again

Sea Floor SpreadingSea Floor Spreading

This process continually adds new material to the sea floor

Question???

Video: http://www.youtube.com/watch?v=GyMLlLxbfa4

Sea Floor SpreadingSea Floor Spreading

• Deep-Ocean Trench: under water canyon where deep oceanic crust bend downward into the mantle

• Subduction: Process by which the ocean floor sinks beneath a deep-ocean trench into the mantle

Video: http://www.youtube.com/watch?v=ryrXAGY1dmE

Sea Floor SpreadingSea Floor Spreading

• Evidence1. molten material2. magnetic stripes (video: http://www.youtube.com/watch?v=BCzCmldiaWQ)

3. drilling samples: drilling sample show younger rocks on the ridge

The Theory of Plate Tectonics

The Theory of Plate TectonicsPlate Tectonics

Plate tectonics: Theory that explains the formation, movement, and subduction of Earth’s plates

The Theory of Plate TectonicsPlate Tectonics

• The lithosphere is broken into separate sections called plates

• The plates fit closely together along cracks in the lithosphere

The Theory of Plate TectonicsPlate Tectonics

How do the plates move?• As the convection currents under the

lithosphere move, they cause the plates to move

• One plate cannot move without effecting another plate

The Theory of Plate TectonicsPlate Boundaries

• Faults: breaks in the earth’s crust• Faults are formed along plate

boundaries

The Theory of Plate TectonicsPlate Boundaries

There are three types of plate boundaries• Transform Boundaries • Divergent Boundaries • Convergent Boundaries

The Theory of Plate Tectonics

TransformBoundary

Motion Sliding past one another

Effect Shallow Earthquakes

Topography Fault

Volcanic Activity

Yes, Ring of Fire

The Theory of Plate TectonicsDivergent Boundary

Motion Move away from one another

Effect Oceanic Lithosphere created

Topo-graphy

Ridge or Rift valley(Mid ocean ridge or African Rift Zone)

Volcanic Activity

Yes – formed from magma in the mantle, Ring of Fire

The Theory of Plate TectonicsConvergent Boundary

Motion Move together or collide

Effect Oceanic Lithosphere destroyed, deep earthquakes

Topography

Trench, mountains, Island arcs

Volcanic Activity

Yes – as the plate submerges, it melts and can rise back up to the surface as lava

The Theory of Plate TectonicsPlate Boundaries

Convergent Boundaries• When plates converge, their

density will depend on what happens

The Theory of Plate TectonicsPlate Boundaries

Oceanic – Continental Convergent Boundary

• Oceanic crust is more dense, so it will go under the continental crust forming trenches and volcanoes

The Theory of Plate TectonicsPlate Boundaries

Oceanic – Oceanic Convergent Boundary

• The more dense oceanic crust will go under the less dense oceanic crust forming trenches and volcanoes

The Theory of Plate TectonicsPlate Boundaries

Continental – Continental Convergent Boundary

• Plate collide up, folding together to create mountains