Plate TectonicsPlate Tectonics

Plate Tectonic VocabularyPlate Tectonic Vocabulary

• Continental drift• Continental Crust• Convection• Convection Current• Convergent

Boundary• Divergent Boundary• Mid-Ocean Ridge• Ocean Trench

• Pangaea• Plate Tectonics• Seafloor Spreading• Subduction Zone• Mid-Atlantic Ridge

CrustCrust

a. What are the two types of crust?

b. Each type of crust is composed of what kind of rock?

c. Which type of crust is denser?

Shorelines are not true boundaries:Shorelines are not true boundaries:1. Continental margin –

where the ocean water

covers the continental

crust

2. Deep ocean basin-

where the ocean water

covers oceanic crust Oceanic crust Continental crust

Oceanic basin

water Continentalmargin

•The ocean water may cover miles of the continental crust

Earth’s Tectonic PlatesEarth’s Tectonic Plates

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• The crust is broken into separate plates.

• How many plates are there?

• T or F Plates are stationary.

Crust

• Convection currents produced in the mantle cause the plates to move.

• As the plates move, everything on them moves along with them.

• Examples:

*The North American plate moves west at a rate of 4 cm per year (1.6 in./yr)

*The Pacific Ocean plate moves northward at the same rate.

Plate Movement

• PLATE TECTONICS

• The continental & oceanic plates on the earth’s surface are constantly moving.

• Many geologists believe that at one time all landmasses were together: supercontinent.

Also called?

Pangaea

Alfred Wegener: •He was a leading scientist in providing evidence that continents were moving.

• CONTINENTAL DRIFT THEORY: *Continents are drifting or moving.

*Break-up of Pangaea occurred around 240 million yrs ago

* Over time continents broke up into smaller pieces and have drifted to their current location

*The continents are currently still moving

uni-graz.at

Alfred Wegener: Continental Drift EvidenceAlfred Wegener: Continental Drift Evidence

Evidence: Evidence: 1. Similarities in coastlines1. Similarities in coastlines2. Similarities in fossil records2. Similarities in fossil records3. Similarities in rock3. Similarities in rock

Continental Drift: Evidence• 180 million years ago, Pangaea began to

break up into separate continents. • Provided evidence of ancient animal and

plant remains from South America, Africa, India, and Australia that were very similar.

• What problem or concern do you think other geologist had with Wegner’s theory?

Could not provide direct evidence that the continents were moving.

Wegener’s Continental Drift Theory

• Where?: Under the Atlantic Ocean

• What? Mountain Range– Mid Atlantic Ridge

the ridge looks like a mountain with a valley running down the center

Who? Harry Hess

Continental Drift Theory: Conclusive Evidence

velikovsky.info

Aerial picture of the Mid-Atlantic Ridge

– Studied rock data from the Mid Atlantic

Ridge

– Found in the center of the ridge is a crack or rift.

– Magma would flow up through this rift

Harry Hess’ Important Observations

Harry Hess Conclusion:

– The ocean floor was moving away from the ridge on both sides.

– As it moved away, it was replaced by rising magma that cooled and solidified into new rock.

– He called this process: Sea Floor Spreading

Sea Floor SpreadingSea Floor Spreading

Thingvellir, the spreading zone in Iceland between the North American (left side) and Eurasian (right side) tectonic plates. January 2003.

Bell Ringer: Plate TectonicsBell Ringer: Plate Tectonics1. What layer of the earth is the plates located?

2.What indirect evidence did Wegener have to hypothesize his continental drift theory?

3.What direct evidence did Hess have to conclude from his research seafloor spreading?

4. From the article “Plate Tectonics: Earth’s Lucky Geology”identify three interesting facts from the article about plate tectonics.

Hess’ Later Observations and Conclusions

– Continued to support sea floor spreading.

– Evidence by further studying the structure, properties, and age of the rock around the Mid-Atlantic ridge.

Scientific Evidence is DynamicScientific Evidence is DynamicScientific evidence presented to the

public is only established after years of sound research in the hands of many scientists. Despite this truth, scientists continue to test these facts as technology advances.

Homework: Read and annotate the article “ UCLA scientist discovers plate tectonics on Mars”. Explain with three supporting facts from this article why the statement above is necessary for science to remain beneficial to humanity.

Plate TectonicsPlate TectonicsHomework due Wednesday:

• Annotate article and answer question related to article.

• Complete sea floor spreading questions.

• Complete questions from plate tectonic worksheet.

• Continue to record seismic activity.

• Quiz: Wednesday

• Test : Friday

Plate BoundariesPlate Boundaries• Plate boundaries are where two plates meet.

• What type of plates can meet?

• There are 3 types of plate boundaries:

1. divergent boundaries

2. convergent boundaries

3. transform boundaries

Divergent BoundariesDivergent BoundariesWhat are divergent boundaries?

Divergent Boundaries• Iceland is above a divergent boundary.• The North American Plate & the Eurasian Plate

Thingvellier,IcelandThingvellier,Iceland

Divergent Boundaries

Mid-Atlantic Ridge: Extends from the Arctic Ocean to beyond the southern tip of Africa & moves 2.5cm per year.

Divergent Boundaries: Divergent Boundaries: African Rift Valley – east African Plate is spreading & has torn Saudi Arabia away from the rest of the African continent forming the Red Sea

Convergent Boundaries Convergent Boundaries What is convergent boundaries?

Convergent BoundariesConvergent BoundariesWhat are the three types of convergent boundaries?

1. Oceanic-oceanic 2. oceanic-continental 3. continental-continental

nature.nps.gov

• Continental convergence form mountain ranges• Example: Himalayan Mountains formed by the

convergence of the Indian and Eurasian Plates.

Convergent Boundaries Continental Convergence:

nature.nps.gov

nature.nps.gov

Himalayan Mountain RangeHimalayan Mountain Range

destination360.com geography.howstuffworks.com

Convergence Boundaries:

Continental and Oceanic Convergence:

• Create trenches and volcanic mountains

• One crust subducts under another.

• Pacific Plate & North American Plate form the Aleutian Islands in the Pacific Ocean off the northeast coast of Siberia

Aleutian Islands

Andes MountainsAndes Mountains

geo1202peru.blogspot.com

Nazca Plate & South American Plate form the Andes Mountains on the western border of the South American continent

Convergent Boundaries:

Oceanic Convergence• Creates trenches, volcanic islands, and

volcanic island arcs • Subduction zone

• Located in the Pacific Ocean near Japan.• Created by ocean-to-ocean subduction.

-Phillipine Plate is subducting under the Pacific Plate

Mariana Trench

Plate TectonicsPlate TectonicsHomework due Wednesday:

• Annotate article and answer question related to article.

• Complete sea floor spreading questions.

• Continue to record seismic activity.

• Complete questions from plate tectonic worksheet.

• Quiz: Wednesday

• Test : Friday

Sea Floor Spreading Model

1. 2.

Use the picture below to help understand the sea floor spreading model you made last week. a.What kind of boundary is represented at #1? (slit?)b.What kind of boundary is represented at #2? (slit?)

Transform BoundariesTransform Boundaries

What is a transform boundary?

•

Transform Boundaries

San Andreas FaultBy Robert E. Wallace, USGS

The Pacific Plate and the North American Plate slide past each other.

Create Earthquakes

Plate TectonicsPlate Tectonics• How does it affect climate?

* Changed the climate over the last 250 million years by constantly creating geological processes (volcanoes;earthquakes) that produced heat and chemicals in the atmosphere that would promote and support life. Climate keeps most water from freezing.

• How does it affect life? • Plate tectonics promotes diversity among animals

by causing isolation due to geographical formations (mountains).

Earth’s Tectonic PlatesEarth’s Tectonic Plates

dpc.ucar.edu