Earth!!!How is it

structured???

Draw what you believe the structure of the

Earth is.Be sure to label all of your

layers!!!

Earth’s Structure

•The crust•The mantle•The outer core•The inner core

Earth’s Structure• The crust

- the “shell” of the Earth - the thinnest layer - the coolest layer - made up of mostly oxygen and silicon

• The mantle - takes up 80% of the volume - warmer than the crust

• The outer core - very hot - made of liquid metal of iron and nickel

• The inner core - hottest layer - made of solid metal

Density of Earth’s Layers

Which layer is most dense??? the core or the mantle

You do the math… D = m/vCore: mass = 33% = .33 volume = 16% = .16

Mantle: mass = 67% = .67 volume = 84% = .84

Results…The core: D = 2.1 The mantle: D= .80

And the winner is….

CORE!!!

The Tectonic Plates

Fit together like a puzzle that covers the Earth…

The Tectonic Plates

Are the plates moving or sitting still???

What is the theory that the plates are moving?

Continental DriftThe Evidence that supports this

theory…- the continents look like they “fit” together like

puzzle pieces. (Pangaea the “Super Continent”)- Fossils of the same plants and animals have been

found on continents that are oceans apart.- The same types of rocks and minerals have been

found on continents that are oceans apart.- Magnetic orientation of rocks on the ocean floor

…more on this later!

Pangaea• Alfred Wegener was a

German climatologist and arctic explorer who suggested the concept of continental drift.

• Continental drift is the idea that the continents move around on Earth’s surface.

Movement of continents

• Wegener thought that the continents we know today had once been part of an earlier supercontinent.

• He called this great landmass Pangaea.

Movement of continents

• The surface of Earth is broken into many pieces like a giant jigsaw puzzle.

• Plate tectonics describes how these pieces move on Earth’s surface.

Evidence for continental drift• Wegener’s belief was a

scientific hypothesis based on observations.

• Continental drift was accepted by all scientists because there was no evidence at the time to explain how continents could move.

Evidence for continental drift• Coal beds stretch across

the eastern U.S. and continue across southern Europe.

• Matching plant fossils are found in South America, Africa, India, Australia, and Antarctica.

• Matching reptile fossils are found in South America and Africa.

• Matching early mammal fossils are found in South America and Africa.

• Fossils in South America and Africa are found in rocks of identical age and type.

• Matching rock types and mountain belts occur in North America and the British Isles, and Africa and South America.

• Evidence of glaciers is present in regions with warm, dry climates. Continents that are close to the equator today were once closer to the South Pole in the distant past.

Let’s Review!!! What are the 4 layers of the Earth? A: crust, mantle, inner and outer core What layer of the Earth is most dense? A: the core What layer of the Earth is hottest? A: the inner core What theory supports the movement of the plates? A: continental drift Name a piece of evidence supporting continental

drift.

Why are the plates moving?

Okay… we know that the plates are moving, but what is making them move?

Convection CurrentsHow does hot air or liquid move?What is something in the Earth’s layers

that depends on this movement? What about cold air or liquid?

Convection Currents

Hot magma cools and

sinks

Magma riseswhen heated

Cooler magma

isheated

Density and Earth’s materials

• The oceanic crust is made mostly of basalt.

• The continental crust is made mostly of andesite and granite.

Density and Earth’s materials• Heating the lower

mantle causes the material to expand.

• Since less dense materials float on more dense materials, a convection current develops.

Floating continents• Earth’s crust is made of different types of rock

that are less dense than the mantle.• It’s hard to imagine rocks floating on other

rocks, but this is what happens inside Earth!

Floating continents

• Earth’s crust floats on the mantle just like the boat.

• A mountain on land is just like the stack of blocks.

• Crust with a mountain sticks down into the mantle.

Floating continents

• The average thickness of continental crust is 30 kilometers.

• A combination of a mountain and its bulge underneath may make the crust as thick as 70 kilometers.

Layers of Earth

• Compare and contrast the details of the different layers of the Earth.

What causes convection in the earth’s mantle?

• A) earth’s rotation

• B) buoyancy

• C) pressure deep within the earth

• D) Breakdown on radioactive isotopes

• Radioactive isotopes produce heat…and heat causes convection currents

Plate Boundaries

What is a plate boundary?A: Where two plates touch each other. (Like two

puzzle pieces)

There are three types of plate boundaries.

The type of boundary depends on how the plates are moving with each other…

Plate Boundaries:

1.DivergentThese plates are moving away from

each other.

Plate Boundaries:

2. Transform FaultThese plates are sliding along side

each other.

Plate Boundaries:

3. ConvergentThese plates are moving into each

other.

Convergent Boundaries:

• There are a couple of different things that can happen at this boundary because there are 2 different types of crust on Earth.

• There is continental crust (crust that is mostly above water: land)

And• There is oceanic crust...that is under the water.

• The continental crust is less dense than the oceanic crust… so what happens when the two different crusts collide at a convergent boundary???

Convergent Boundaries

A: Since the Oceanic crust is more dense it dives beneath the Continental crust

= SUBDUCTION ZONE (picture A)

Convergent Boundaries

• Continental–Continental collision (picture C)

The crust buckles UP and forms large mountains.

Geological FormationsAt each boundary different

geological formations (mountains, volcanoes, trenches, earthquakes, faults, etc.) occur because of the movement of the plates.

Lets look at what forms at each boundary…

Geological Formations – Divergent

Seafloor SpreadingMid-oceanic ridges and Volcanoes

Geological Formations – Convergent (NO subduction)

Large Mountains

Geological Formations – Convergent (WITH subduction)

Volcanoes, Mountains, and Oceanic Trenches, island arcs

Geological Formations – Transform Fault

Faults and Earthquakes

Question???

• We now know that new rock is created at divergent boundaries b/c of seafloor spreading.

• Explain why the Earth’s mass is NOT increasing as a result.

• Use the Law of Conservation of Matter in your answer.

Let’s Find Some of These On a MAP…

•Just by looking at a 3-D map you can determine what type of plate boundary there is b/c of the formations that occur!!!

Let’s Review…• Convergent Subduction Zone

occurs at the Peru-Chile Trench and Andes Mts. between the NAZCA and SOUTH AMERICAN PLATES.

• Convergent (NO subd.) occurs at the Himalaya Mts. between the INDIAN and EURASIAN PLATES.

• Transform Fault occurs at the San Andreas Fault (in California!!!) between the NORTH AMERICAN and PACIFIC PLATES.

• Divergent (Mid-Oceanic Ridge) occurs at the Mid-Atlantic Ridge between the NORTH AMERICAN and AFRICAN PLATES.

• The RING OF FIRE occurs around the edge of the entire PACIFIC PLATE. (Earthquakes and Volcanoes)

Density and Earth’s materials• Today aluminum and silicon, which have

low densities, are common in Earth’s crust. • Earth’s inner and outer cores are composed

mostly of very dense iron.

Final Exam Focus• Be able to locate and label the layers of

the Earth.• Know where the major plates are on a

map.• Be able to describe the geological

processes that are occurring at given boundaries on a map.

• Be able to locate on a map: a convergent boundary w/ subduction, the ring of fire, a divergent boundary, and a transform fault boundary.

• Know the supporting evidence of plate tectonics.

• Know the best possible explanation for the movement of the plates.

• Know what Pangaea is.

There are 18 questions on your final exam dealing with PLATE TECTONICS! BE READY!