Plate Tectonics

Goal 2.1

Lesson 1

Plate Tectonics: An Overview

Think About It…

Look at the map below. Which two

continents look like they‘d fit together?

Focus Question…

How do Earth’s tectonic plates cause…

…volcanoes to form? …earthquakes to occur?

…Earth’s surface features to form?

Continental Drift… 1. What is the theory

of continental

drift?

The

continents

had once

been joined

as a single

landmass that

split (drifted)

apart. http://rosalieee.files.wordpress.com/2009/01/pangea-continental-drift.jpg?w=596&h=489

Continental

Drift…

2. What was

Pangaea?

the

ancient

super-

continent

http://pubs.usgs.gov/gip/dynamic/historical.html

3. Evidence Supporting Continental

Drift…

a. the puzzle-like fit continents on either side

of the Atlantic Ocean

http://earthscience.wordpress.com/2007/04/13/day-143-continental-drift-puzzle/

Evidence Supporting Continental

Drift… Rocks and Fossils

b. Rock formations

& fossils on both

sides of the

Atlantic Ocean

match.

http://choralemaacher.lu/continental-drift-evidence-mountains

Evidence Supporting Continental

Drift…Fossils

http://abyss.uoregon.edu/~js/images/fossil_break.gif

Evidence Supporting Continental

Drift…Climate

c. Climate changes...

Coal deposits in

Antarctica (warmer

and farther north)

Glacial erosion in India,

Africa, and Australia

(colder and farther

south)

http://blue.utb.edu/paullgj/physci1417/Lectures/Gondwanaland_Glaciations.JPG

Seafloor Spreading…

1. The theory of seafloor spreading

states…

new ocean crust is formed at the ridges

and destroyed at trenches.

Seafloor Spreading…

http://higheredbcs.wiley.com/legacy/college/levin/0471697435/chap_tut/images/nw0125-nn.jpg

How we know what’s down there!

http://marinesciencetoday.com/2009/05/06/new-antarctic-sonar-images-reveal-clues-to-sea-level-rise/

https://directory.eoportal.org/web/eoportal/satellite-missions/t/topex-poseidon

2. Preview of the Ocean Floor…

a. An ocean ridge is…

vast, underwater mountain range – the

longest on Earth!

b. A deep sea trench is…

narrow, elongated depression in the

ocean floor - deepest part of the ocean –

11 km deep!

See next slide…

The Ocean Floor…

Evidence for Seafloor Spreading…

a. Ocean rocks and sediments are

younger at the midocean ridges.

Evidence for Seafloor Spreading…

b. Magnetism –

Basalt provides an accurate

record of ancient

paleomagnetism.

i. Earth has had a series of

magnetic reversals or

changes in its magnetic field.

ii. These are recorded in the

ocean floor.

The magnetic pattern on

either side of a midocean

ridge is a mirror image.

DRAW ME!!

DRAW ME!!

How Seafloor Spreading Occurs…

Step 1: Magma rises and fills the gap.

Step 2: Magma solidifies to form new crust.

Step 3: New crust is continually made and pushes the

older crust to the outer edges of the ocean.

http://www.uwsp.edu/geo/faculty/ritter/glossary/S_U/sea_flr_spread.html

See next slides…

A Bigger View!

http://www.moorlandschool.co.uk/earth/tectonic.htm

The Theory of Plate Tectonics…

1. The theory of plate

tectonics …

Earth’s rigid

crust and upper

mantle is broken

into large plates.

http://geology1a-1.wikispaces.com/Plate+Boundary+images+and+captions

2. Plate Boundaries…(Add to

Lesson 1.)

a. Divergent – plates separate

b. Convergent – plates are moving toward each other

c. Transform – slide horizontally past each other

Click here to investigate the boundaries…

http://geology.com/plate-tectonics.shtml

The Plates…

Australian plate - pink or lighter orange, Nazca & Scotia plates – lighter blue

Lesson 2

Plate Tectonics – Divergent

Boundaries

Think About It…

Why do some parts of Earth have

volcanoes and earthquakes and

others don’t?

Focus Question…

What geologic activity occurs at

a divergent plate boundary?

Plate Boundaries: The Big Pic…

http://geology1a-1.wikispaces.com/Plate+Boundary+images+and+captions

Divergent Boundary…

1. A divergent boundary is one

where the plates are separating

or moving apart.

2. Geological Processes

a. High heat flow – magma pushes up into

the rift valley.

2. Geological Processes

b. Volcanoes – formed by the magma

rising at the rift valley

2. Geological Processes

c. Earthquakes – caused by the magma

breaking rocks on its way to the surface

Divergent Boundaries…

3. Divergent boundaries form rift valleys

where… magma rises, solidifies, &

pushes plates apart. DRAW ME!!

Divergent Boundary…

4. The underwater

mountain range

formed at

divergent

boundaries in

every ocean is…

The midocean

ridge

5. Examples - Iceland…

East Africa Rift Valley…

http://geology.com/articles/east-africa-rift.shtml

The Midocean Ridges

http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/p_midoceanridges.html

Lesson 3…

Convergent Boundaries

Think About It…

Where do many of our most

devastating earthquakes occur?

Focus Question…

What geologic activity occurs at

a convergent plate boundary?

Plate Boundaries: The Big Pic…

http://geology1a-1.wikispaces.com/Plate+Boundary+images+and+captions

Convergent Plate Boundaries…

• There are 3 types of convergent plate boundaries – depending on their locations… – Ocean/continental

– Ocean/ocean

– Continental/continental

We will look at each type separately…

Convergent

Boundaries:

Ocean/Ocean

1. Subduction is…

… the process of one plate going under another.

The process of subduction creates a deep-sea trench.

2. The underground edge of the subducting plate melts because… it is pulled deep into Earth’s crust.

Melted crust rises to form a volcanic island arc.

Effects of Plate Snapping…

3. Two devastating

effects of a

plate snapping

back are…

a. Earthquakes

b. Tsunamis

• See clips…

http://d3sdoylwcs36el.cloudfront.net/map_of_thye_areas_hit.gif

http://tsunami2004videoarchive.com/tsunami_video_key_video.htm

Convergent Boundaries:

Ocean/Ocean

4. The type of fault found at this

boundary is…

… reverse

http://www.artinaid.com/wp-content/uploads/2013/04/ReverseFault.gif

Convergent Boundaries:

Ocean/Ocean

http://www.indiana.edu/~geol116/week7/conver.jpg

Let’s

Draw! DRAW ME!!

Convergent Boundaries:

Ocean/Ocean

5. Examples of

this are…

a. Mariana

Islands

b. Japan

c. Indonesia

Convergent Boundaries:

Ocean/Ocean – Another Example

The Japanese Islands

Convergent Boundaries:

Ocean/Continental

1. The oceanic plate subducts under the

continental plate. (It is denser.)

2. A volcanic mountain range forms on

land above the subduction zone.

3. Examples include Andes Mountains (S.

America) and the Cascade Mountains

in N. America)

Convergent Boundaries:

Ocean/Continental

http://www.100destinos.com/imagenes/los-andes-chile.jpg

http://www.worldtravelattractions.com/cascades-cascade-range/

The Andes of S. America

The Cascades of N. America

Convergent Boundaries:

Ocean/Continental

http://elearning.stkc.go.th/lms/html/earth_science/LOcanada4/403/images/3_1.jpg

Let’s

Draw! DRAW ME!!

Convergent Boundaries:

Continental/Continental

1. A folded mountain range is formed when two

continental plates collide. (They are both too

thick to go under.)

2. Examples include the Himalaya Mountains

and the European Alps.

Let’s

Draw!

DRAW ME!!

The Appalachian Mountains and

the Piedmont…

• They started as a continental fragment and a volcanic island arc about 700–600 mybp.

– The continental fragment moved west & became the Blue Ridge Province. (500-400 mybp)

– The island arc moved west & became the Piedmont Province. (400-300 mybp)

– The folded Valley and Ridge (c/c) formed when the N. American and African plates collided. (300-260 mybp)

Lesson 4

Transform Boundaries

Transform Boundaries… 1. Transform refers to “moving across.”

2. At transform boundaries, crust is only deformed or fractured.

3. Volcanoes and mountains don’t form here because there is NO vertical movement of the plates.

4. The type of faults formed here are called strike-slip faults

5. Transform boundaries are characterized by shallow earthquakes.

DRAW ME!!

Haiti, 1/2010 (7)

6. Examples include:

San Andreas Fault in California

Haiti

Plate Boundary Activity…

• http://geology.com/plate-tectonics.shtml

Causes of Plate Movements…

1. Large-scale

motion in the

mantle drives

the movement

of the plates.

http://www.nakedscience.org/mrg/Plate%20Tectonics%20Lecture%202_files/image018.jpg

Causes of Plate Movements…

2. Definitions…

a.Mantle – layer of

Earth beneath

the crust

b.Asthenosphere

– partially molten

layer of the

mantle

Causes of Plate Movements…

Definitions…

c. Convection –

transfer of thermal

energy by the

movement of heated

matter

d. Convection current

– pattern of motion

produced by warmer

matter moving up and

cooler matter sinking

http://library.thinkquest.org/C003124/images/convect.jpg

Causes of Plate Movements…

3. The tectonic plates move by…

a.… The rising part of the convection

current spreads out as it reaches the upper

mantle which lifts and splits the lithosphere

at divergent plate boundaries.

b.… The downward part of the convection

current creates a sinking force that pulls

tectonic plates downward at convergent

boundaries.

Causes of Plate Movements…

3. The tectonic plates move by…

c. … Ridge push - the force created by the

weight of the uplifted ridge which pushes an

oceanic plate towards a trench. (at a

subduction zone)

d. … Slab pull - process in which the weight

of the subducting plate helps pull the trailing

lithosphere into the subduction zone.

Causes of Plate Movements… DRAW ME!!

Causes of Plate Movements…

http://www.fas.org/irp/imint/docs/rst/Sect2/Sect2_1b.html