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Plate Tectonic Notes. May 4, 2012. I. Earth’s Interior. A. Layers of the Earth 1. Crust : thin and solid outermost layer of Earth above the mantle

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I earth s interior
I. Earth’s Interior

A. Layers of the Earth

1. Crust: thin and solidoutermost layer of Earth above

the mantle

a. Continental crust is lessdense and thicker(20-40km) (12-25 mi) than oceanic crust, which is more dense and thinner(5-8km) (3.1-4.9 mi)


Lithosphere asthenosphere
Lithosphere & Asthenosphere

  • Lithosphere(60 mi thick) is made up of the crust and the upper portion of the mantle

  • Asthenosphere-hot, plastic portion of the mantle that can flow

    -soft rock in the

    asthenosphere

    circulates by

    convection currents

    & this results in slow

    movement of plates


Plate tectonic notes

2. Mantle: layer of rock between the Earth’s crust and core

a. Denser than the crust

b. Outermost part is solid and rigid, but as you move closer to the core, the mantle becomes soft and easily deformed (like gum..hot plastic portion of mantle)

1. Called the asthenosphere

  • *Also, very hot

  • (1200℃ or 2280℉)


Plate tectonic notes

3. OuterCore: Liquid metal outer edge of core

a. Composed mainly of iron and nickel

4. InnerCore: Solid metal inner core

a. Composed mainly of iron and nickel

*Temps are

thought to be

above 10,800℉

*Earth’s center

has radioactive

isotopes that do

fission & release

a ton of heat

energy


Plate tectonic notes

B. As you travel from crust into the core, the temperature increases

1. Temperatures from 375oC at the crust to over 6000oC (10,800 ℉)in the inner core

C. Thermal Energy Transfer

1. Material moves with the Earth as a result of conduction (transfer thermal energy from individualatom to

individualatom) and

convection currents

(hot material rises &

cool material sinks

back to the core)


Plate tectonic notes

D. Evidence for Characteristics of Layers

1. P-waves and S-waves (see below)

*P Waves travel through liquids & solids but S Waves cannot travel through liquids


Ii continental drift
II. Continental Drift

A. Theory that Earth’s surface is made of large movableplates

1. Alfred Wegener was a German scientist who first proposed the idea that the continents of the Earth were once one large supercontinent

a. Called this supercontinent Pangaea


In 1910 alfred wegener begins to wonder
In 1910 Alfred Wegener begins to wonder.

He thought that:

  • All the continents were stuck together at one time (300 million years ago?).

  • Continental drift = slow movement of continents over Earth’s surface.


Supercontinent called pangea
Supercontinent called PANGEA

Pangea means all lands


Wegener s evidence

Wegener’s summary was based on various careful observations:

#1 - All of the coastlines of the continents seemed to fit together like puzzle pieces.

Wegener’s Evidence


Wegener s evidence1

#2 - Fossil evidence: observations

Identical fossils found on different continents

Wegener’s Evidence


Wegener s evidence2

#3 - Glacial Evidence: observations

  • Large ice masses carve grooves in the rocks over which they flow.

  • Such masses tend to flow outward (generally downhill) from a central locality.

Wegener’s Evidence


Wegener s evidence3

#4 - observationsRock Ages:

the framework of rock ages showed strong correlation across the Atlantic, as did mountain ranges of similar age.

Wegener’s Evidence


Plate tectonic notes

B. Early evidence for Continental Drift observations

#5. Migration patterns of animals have not changed since it was supercontinent.


Plate tectonic notes

C. observationsRecent evidence for Continental Drift

1. Magneticpolarity bands near mid-ocean ridge [Fig 6, p.703]

a. Alternating magnetic bands, normal versus reversed, on new ocean floor

2. Age of rocks relative to the mid-ocean ridge: the farther away from the mid-ocean ridge, the older the rock


Iii plate tectonics
III. Plate Tectonics observations

A. Lithosphere is made up of the crust and the upper portion of the mantle

1. Divided into 7 major plates and several smaller plates called tectonic plates

2. Continents are embedded into the tectonic plates

3. Plates “float” on the asthenosphere

-hot, plastic portion of the mantle that can

flow

-soft rock in the asthenosphere circulates

by convection currents & this results in

slow movement of plates



Plate tectonic notes

B. observationsPlateTectonics: the theory that explains how the outer parts of the Earth change through time

1. Also explains the relationships between continental drift, sea-floor spreading, seismic activity, and volcanic activity


Iv plate boundaries
IV. Plate Boundaries observations

A. Divergent Boundaries: two plates move apart creating a gap between them

1. Causes mid-oceanridges to form

a. Less dense magma rises up

in between the

two separating

plates creating

new oceanfloor

b. Gap between the

two plates is called

a riftvalley

c. Most studied mid-ocean ridge is Mid-Atlantic Ridge



Plate tectonic notes

B. observationsConvergent Boundaries: two plates are coming together

1. Forms oceantrenches, volcanoes, &/or mountains

a. Subduction zone: process by which one lithospheric plate moves beneath another as a result of tectonic forces

1. Oceantrench: forms between 2

oceanic plates or oceanic plate and

continental plate

a. Older plate is denser, so it

sinksbelow the other plate

b. Can be extremely deep


Plate tectonic notes

2. Volcanoes are formed as the observationssubducting plate is melted and the magma rises to surface on other plate

b. Colliding tectonic plates create mountains

1. Two continental plates collide and the land is pushed upward creating mountains

2. Example: Himalayas


Common events at plate boundaries volcanoes
Common Events at Plate Boundaries: observationsVolcanoes



Hot spots
Hot Spots boundaries?

  • A hot spot is an area of persistent volcanic activity that comes from unusually hot areas of the mantle-core boundary.

  • Hawaii, Iceland, and Yellowstone are examples of hot spots.


Plate tectonic notes

C. boundaries?TransformFault Boundaries: two plates sliding past each other

1. Fault: crack in Earth created when rocks on either side of a break move

2. One cause of earthquakes

3. Example: San Andreas Fault (from Mexico to California)


V earthquakes
V. Earthquakes boundaries?

A. As plates move past each other, pressure builds up and eventually the stress becomes so great it causes the rock to crack

1. Focus: exact point inside Earth when an earthquake originates

2. Epicenter: point on Earth’s surface directly above an earthquake’s focus


Plate tectonic notes

B. Energy is transferred by boundaries?waves

1. Longitudinal waves (P Waves): Move faster through rock, so first waves to reach recording stations

2. Transverse waves (S Waves): Move more slowly, so arrive second to the recording station

3. Surface waves: seismic waves that can only move through solids


Common events at plate boundaries earthquakes
Common Events at Plate Boundaries: boundaries?Earthquakes


Earthquake effects tsunami
Earthquake Effects: Tsunami boundaries?

A tsunami is a giant wave or sequence of waves produced by large water displacements. These are most commonly caused by underwater earthquakes.

Tsunamis can be destructive long distances from their sources.


Plate tectonic notes

C. boundaries?Seismograph: machine that records the movements produced by an earthquake

1. Use seismographs to investigate the Earth’s interior

2. Differences in velocities of the waves indicate the type of material the waves travel through

a. Scientists constructed the model of Earth [Fig. 19, p.712]


Plate tectonic notes

D. boundaries?Richter Scale: a scale that expresses the magnitude of an earthquake

1. Range from 2.0 to 10.0 magnitude

2. No earthquakes have ever been recorded at 9.0 or 10.0