ch.17 plate tectonics test

___________ major plates and several minor plates

8-12

Which feature is associated with a continental-continental plate boundary?

A mountain range

Which landform results from divergence of continetal crust?

A rift valley

What happens when an oceanic plate converges with a continental plate?

A trench and a mountain range with many volcanoes form

in 1912, _____________ ____________ proposed a hypothesis he called ______________ _____________.

Alfred Wegner, continental drift

plate boundaries

Areas of instability in the crust

Oceanic crust is made mostly of

Basalt

Lithosphere =

Basalt (heavy,dense) exception is continents granite (lighter)

Compare and contrast ridge pull and slab pull.

Both are processes associated with plate movements. Ridge push is a process in which the uplifted ridge is thought to push the oceanic plate toward the subduction zone. Slab pull is a process where by the weight of a subducting plate helps to pull the trailing lithosphere into the subduction zone.

Tectonic plates interact at places called plate

Boundaries

continental-continental convergence

Collision of these types of plates form mountains. No melting occurs. (Ex. The Himalayas)

Explain the process of convection.

Convection is the transfer of thermal energy by the movement of heated matter. Heating matter causes it to expand and decrease in density. This warmed matter is forced upward as a result of buoyancy. The cooler part of the matter is pulled downward as a result of gravity. This up-and-down flow creates a pattern of motion called a convection current.

Places where tectonic plates come together are called

Convergent boundaries

Places where tectonic plates move apart are called

Divergent boundaries

The Mid-Atlantic Ridge is an example of

Divergent boundary

What do plate boundaries cause?

Earthquakes, volcanoes, mountain building

Describe the formations of convection currents in the mantle.

Even though it is a solid, the upper mantle can flow like a soft plastic. Convection currents are set in motion by the transfer of energy between Earth's hot interior and cooler exterior. Regions of hot mantle are less dense than areas of cooler mantle and are slowly forced toward the crust. Cooler parts of the mantle sink back toward the core. The convection currents that result are probably set in motion by subducting slabs.

What geologic features are associated with each type of convergent boundary?

I'm not typing all those sentences again :| ..... just know this question.

What is one hypothesis regarding the formation of a divergent boundary on a continent?

Large continental masses may act as insulating blankets. The underlying mantle becomes warmer and causes the upward leg of a convection current to develop. Over time, the continent splits.

Mantle convection

Mechanism for plate movement = thermal convection cells in the asthenosphere ( molten portion of the mantle) push and pull the plates

What can happen when two oceanic plates converge and one is subducted into the mantle?

Melted magma erupts and forms an arc of islands

What happens along a divergent boundary?

New ocean crust forms

Where are divergent boundaries found?

On the sea floor where they form ocean ridges

Where are most divergent boundaries found?

On the seafloor

Which theory states that Earth's crust and rigid upper mantle move in different directions and at different rates over Earth's surface?

Plate tectonics

Plates

Rigid, mobile pieces of earth's lithosphere (solid,crust and upper mantle)

What forms when two oceanic plates converge?

Subduction zones

Explain how the parts of a convection current in the mantle are related to plate movements.

The rising part of a convection current spreads out as it reaches the upper mantle and causes lateral and upward forces. These forces lift and split the lithosphere at a divergent boundary. The downward part of the current occurs where a sinking force pulls plates downward at convergent boundaries.

Explain the theory of plate tectonics

The theory that explains how large pieces of the lithosphere, called plates, move past each other and change shape.

Slab pull

The weight of a subducting plate helps pull the trailing lithosphere into the subduction zone

At which tectonic plate boundary do plates slide horizontally past each other?

Transform boundary

Convergent boundaries are classified as

Type of crust involved

Which is NOT associated with transform boundaries?

Volcanoes

What are associated with divergent boundaries?

Volcanoes and earthquakes

subduction results in the formation of ___________.

a deep-sea trench.

Transform boundaries

a place where two plates slip past each other, moving in opposite directions

what is the first critical discovery ?

age of rocks on ocean floors: - younger near ocean ridges -older near trenches - ** age increases with distance from ridge (ocean crust is geologically

the partially molten ____________ is thought to contain cenvection currents responsible for plate movement.

asthenosphere

____________ plates are usually composed of granite.

continental

mid-ocean ridges occur at ___________ boundaries.

divergent

rising convection currents are associated with _________.

divergent boundaries

What are three types of plate boundaries?

divergent, convergent, transform

Rock samples taken near ocean ridges are older than rock samples taken near deep-sea trenches.

false

continental drift

hypothesis stating the earth's continents had once been joined as a single landmass called pangea

fossil evidence that supported wegner's hypothesis of continental drift included

land dwelling animals

Paleomagnetism

magnetic records in rocks -paatterns of normal vs. reversed polarity - basalt- rich in iron, cools, and hardens to become locked in place, shows earth's magnetic field at that time

in the early 1900's, wegners theory was rejected because

most people thought that the continents and ocean basins were permenant fixed features on earth's surface

when two continental plates collide, what is the most likely result?

mountain building

Alfred wegner proposed the continents started ___________ ____________ about 200 million years ago.

moving apart

certain rock formations on the east coast of north america closely match those on the west coast of europe. this means

north america and europe were once joined.

what is the second critical discovery?

ocean floor sediments -ocean floor sediments are a few hundred meters thick; continents sedimentary rock is a few km-20 km thick

features found at divergent boundaries include__________.

ocean ridges.

when an oceanic plate collides with a continental plate, the __________ plate typically subducts.

oceanic

What are the three types of convergent boundary?

oceanic-oceanic , oceanic-continental, continental- continental

Where do transform faults occur?

on ocean ridges and divergent boundaries

the study of earth's magnetic record is known as____________.

paleomagnetism

divergent boundary

places where two tectonic plates are moving apart

convergent boundaries

places where two tectonic plates are moving toward each other

Explain what happens at the three types of plate tectonics.

plates come together at convergent boundaries. Plates move away from one another in divergent boundaries. Plates move horizontally past one another in transform boundaries.

continents are not pushing through the ocean crust as wegner proposed, they

ride with ocean crust as it moves away from ocean ridges

___________ is a process where the weight of an uplifted ocean ridge pushes an oceanic plate toward a subduction zone.

ridge push

which of the following evidence was used by wegner to support his hypothesis?

rock types and ages

Theory of Plate Tectonics

states that Earth's crust and rigid upper mantle are broken into enormous slabs called plates

oceanic-oceanic convergence

subduction occurs- creates a deep sea trench and arc of volcanic islands (Ex. Marians trench and islands)

oceanic-continental convergence

subduction occurs- creates a trench and series of volcanoes erupting ( Ex. Andes Mountains)

Ridge push

the weight of the uplifted ridge is thought to push an oceanic plate toward the trench formed at the subduction zone

harry hess

theory of seafloor spreading- states that new ocean crust is formed at ocean ridges and destroyed at deep-sea trenches.

What and where do divergent boundaries sometimes form?

they create rift valleys and form on continents

Sonar and magnetic studies (magnetometer) of ocean rocks and sediments led

to the proposal of the theory of seafloor spreading.

Crust is neither destroyed nor formed along which of the following boundaries?

transform

what two problems was with Wegner's theory?

what caused the contenents to move? how could the continents move without shettering?

compared to ocean crust near deep-sea tranches crust near ocen ridges is___________

younger

In a transform boundaries....

-crust is deformed or fractured -characterized by long faults and shallow earth quakes - Ex. The San andres fault

Evidence for Continental Drift

1) coastline shapes match-up 2) rock formations/ landform feautures match 3) similair fossils in widely seperated areas 4) climatic data (coal in Antarctica, etc)

2 topographic features were discroved:

1) deep sea trenches- deepest in the pacific-marians trench 2) ocean ridges- form from the longest continuous mountain range on earth- mid- atlantic ridge