sea floor spreading

19. What happens when two plates carrying continental crust collide? Does one subduct? Why or why not?

No, since both sides generally have the same density neither is dense enough to sink very far into the mantle.

3. How do mid-ocean ridges form?

Underneath the ocean, deep in the earth convection currents bring molten material up to the upper mantle. This material rises through faults (cracks) between oceanic plates that are moving away from one another. This material fills the cracks, hardens, and forms new crust. This process repeats many times and eventually forms an underwater mountain range.

15. When two plates collide, what determines which one comes out on top?

When two plates collide the density of the plates determines which one comes out on top. The plate with the greater density will subduct (go under) the less dense plate.

21. Is crust created or destroyed at a transform boundary?

neither created or destroyed

8. What is the name given to an area where tectonic plates meet?

plate boundary

17. Compare the thickness and density of continental crust to oceanic crust.

continental crust is thicker, but oceanic crust is more dense.

7. What force do geologists believe is responsible for the movement of the continents?

convection currents in the mantle

11. Plates at different types of boundaries move

differently

20. What event often occurs along transform boundaries?

earthquakes

what force is acting on the oceanic crust to pull it down beneath the trench

gravity

what radicle idea did hess propose

he proposed that a process he called sea floor spreading was continually adding new material (crust)to ocean floor

who was harry hess and what did he study

he was an american geologist who studied mid ocean ridges

what happens to oceanic crust at deep ocean trenches

it eventually sinks back into the mantle

the ocean floor has mountains chains that are as impressive as those on land. what are these under water mountains called?

mid ocean ridges

where do mid ocean ridges form

mid ocean ridges form along divergent boundaries (where two plates pulling away from one another )in every part of the worlds ocean

12. Most divergent boundaries occur along

mid-ocean ridges where sea-floor spreading occurs.

how did scientist determine the location and size of these under water mountain chains

sonar

14. What do we call it when two plates converge?

A collision

13. What is a rift valley? Where can a good example be found?

A rift valley is formed when a divergent boundary develops on land (the Earth's plates in that area move apart) and a deep valley forms. One of the most well known examples of a rift valley can be found in East Africa.

There are three kinds of techtonics plates

A. Convergent boundary plates come together or move toward each b. divergent boundary plates move apart or away from each other in opposite directions plates slide past one another going in opposite directions (like rubbing hands together)

9. Plate movement is measured by instruments mounted onto satellites that orbit the Earth. The plates move at a rate of

1 to 24 centimeters per year.

5. J. Tuzo Wilson, a Canadian scientists, developed the theory of plate tectonics based on what three (3) observations?

1) that there are cracks in the continents similar to the cracks found on the ocean floor 2) sea-floor spreading 3) continental drift

Every___________(___________ ) Years new rock .forms at the mid ocean ridge move across the ocean and sinks into a trench recycling itself

200million (200,000,000)

How does the concept of sea floor spreading help support the idea that continental drift thereby supporting wegeners theory

As magma is thrust up and hardens forming new crust the ocean floor on both sides of the mid ocean ridge move outward carrying the continents along with them

What happens to oceanic crust at deep ocean trenches

It eventually sinks back into the mantle

What happens to the rock oceanic crust is formed

Old rock is pushed out under thr ridge

Explain the the process of sea floor spreading

Sea floor spreading occurs when the sea floor spreads apart along divergent boundries and forms the mid ocean ridge. Magma is pushed up though cracks in the crust along the mid ocean ridge .as the magma is thrust up and hardens it forms new crust and the ocean floor on both sides and hardens it forms new crust and the ocean floor on both sides of the mid ocean ridge

What technologies existed during Hess lifetime that did not exist during wegeners that allowed Hess to prove the theory of sea floor spreading

Sonar submarines tools for deeper oceanic drilling

The pacific ocean covers approximately 30%of the earth surface but it's is shrinking

Subduction in the many deep ocean ridge move trenches is occurring faster than new crust is being added (more crust is sinking back into the mantle at the deep ocean trenches than is being created along the mid ocean ridges)

What is this povecess called

Subuction

16. What happens to the density and temperature of oceanic crust as it spreads away from the mid-ocean ridge?

The density increases and the temperature decreases (the crust gets cooler)

5. Why is the country of Iceland unique

The mountains of the mid-ocean ridge rarely are found above the surface of the ocean, but such is the case in Iceland. A part of the Mid-Atlantic Ridge rises above the surface in the North Atlantic Ocean and forms the country of Iceland.

18. When oceanic crust collides with continental crust, what happens? Explain why it happens.

The oceanic crust will subduct (go under) the continental crust because it is more dense.

6. What is the theory of plate tectonics?

The theory of plate tectonics states that the Earth's tectonic plates are constantly moving in slow motion.

2. These different types of boundaries occur on land and in the ocean all around the world. You are not expected to know each area, but should be able to use symbols provided to identify the different types of boundary. These are some you SHOULD know and that we have discussed in class:

a. convergent boundaries between the Eurasian and Pacific Plates and the Eurasian and Indo- Australian plates b. divergent boundaries between the North American and Eurasian Plates and South American and African Plates c. transform boundaries between part of the North American and Pacific Plates (northern California)

3. What type of landforms (trenches, volcanic mountains, volcanic islands, rift valleys) are created when:

a. two ocean plates diverge mid-ocean ridges, mountain ranges, central valley (new crust is formed) b. two continental plates diverge rift valley, volcanoes c. an oceanic and a continental plate converge subduction zone, volcanic islands, trenches (crust is destroyed) d. two oceanic plates converge trench

10. The North American Plate and the Eurasian plates are moving

apart at a rate of about 2.5 centimeters per year.

where does sea floor spreading begin

at the mid ocean ridge

what process called

subduction

4. Earth's lithosphere, its solid outer shell, is broken into separate sections called

tectonic plates.

how do mid ocean ridges form

underneath the ocean deep in the earth convection currents bring molten material up to upper mantle this material rises through fault cracks between oceanic plates that are moving away from one another

PLATE TECTONICS 😎

😎⚽️😀😃