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Earth's Layers 4
6th Grade Science: Unit 5 - Theory of Plate Tectonics
| Question | Answer |
|---|---|
| Describe the Theory of Plate Tectonics. | The theory starts with the idea of Continental Drift. The Earth once had a single land mass called Pangea, that broke apart into pieces that drifted away to become the major continents of today. |
| Name 3 pieces of evidence that support Continental Drift | • Identical types of fossils found in Africa and South America • Continents can “piece” together with the same rock formations • Glacial deposits left by same sheet of ice |
| Describe how the continents are moving because of sea floor spreading | Lava erupts from the center of the valley area in the Mid Ocean Range and pushes the ocean floor away on the other side |
| Running down the middle of the oceans are long mountain chains with valleys in the middle called _______. | Mid Ocean Range |
| The Mid-Atlantic Ridge is separating at approximately ___cm per year. | 4 cm |
| _________ match up on either side of the ridge as the poles reverse themselves. | Magnetic Stripes |
| Rocks look like _____ when lava cools in the ocean. | Pillows |
| Why doesn’t the ocean floor keep getting bigger? | The ocean floor is also being destroyed at Subduction Zones |
| Parts of the ocean floor are going back down into the _______________ at subduction zones. | mantle |
| Where are the subduction zones located? | trenches in deepest part of the ocean.(Ex: Marianas Trench) |
| What does the Theory of Plate Tectonics explain? | the formation, movements, collisions, and destruction of the Earth’s crust. |
| Describe 2 hypotheses that describe how do the plates move? | • One hypothesis is that large convection currents within the mantle move the plates. • Movement is caused by differences in temperature causing a rising and sinking cycle. |
| The lithosphere is divided into ___ major and minor plates. | 7 |
| Plates move at different ____ in different ____. | different speeds and different directions |
| Define: Plate boundaries | the area where two plates meet. |
| Name 3 Types of Plate Boundaries | 1) Divergent Plate Boundary 2) Convergent Plate Boundary 3) Transform Plate Boundary |
| Define Divergent Plate Boundary | Boundary where plates move apart (ex: Great Rift Valley/Africa Mid ocean Ridges) |
| Define Convergent Plate Boundary | Boundary where plates come together (ex: Himalayan mountains, Japan, and Philippines) |
| Define Transform Plate Boundary | Boundary where two plates slide along side each other (ex: San Andreas Fault/San Francisco) |
| Name the two types of divergent or constructive boundaries | Mid Ocean Ridge and Rift Valley |
| Define: Mid Ocean Ridge | New ocean floor, mountains, earthquakes and volcanic action occur when an ocean plate spreads apart |
| What is the largest mountain range in the world? | Mid Atlantic Ridge |
| Define: Rift Valley | Continent starts to split apart forming a rift valley and eventually a seaway and then an ocean. Volcanic activity and earthquakes occur in these areas. (Ex: African Rift Valley) |
| Convergent Boundaries form when two tectonic plates come ______ each other. | towards |
| Name three types of convergent boundaries or destructive boundaries. | 1) continent-continent 2) ocean-ocean 3) continent-ocean |
| Describe a Continent-Continent convergent boundary | mountains form and earthquakes occur when continental plates run into each other and fold upwards. (Ex: Himalayas and Alps) |
| Describe an Ocean Plate-Ocean Plate convergent boundary | Volcanic island arcs, trenches & earthquakes occur when older ocean plate subducts under a younger ocean plate. (Ex: Japan, Aleutian Islands-off Alaska, Philippines, Tonga Islands, Marianas Trench). |
| Describe an Ocean Plate-Continent Plate convergent boundary | Mountains, volcanoes and earthquakes occur as an ocean plate subducts under a continental plate. The Oceanic plate melts; less dense magma rises to form volcanoes. (Ex: Andes, Cascade Range, Sierra Nevada) |
| Strike-slip or transform boundaries occur where? | where two plates slide along each other. |
| What occur in strike-slip or transform boundary areas? | Earthquakes (Ex: San Andreas Fault in California). |
| Do the Hawaiian Islands occur by a plate boundary? | No, these islands form as the Pacific plate moves over a hot spot in the mantle. |
Created by:
Engle Family
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