Plate Boundaries

convergent plate boundaries: magma is generated thru a process called

"flux" melting

why volcanoes appear 100km from trench... same composition

1. continental collision when oceanic lithosphere destroyed 2.no active subduction (no magma source or volcanoes) 3.continents do not do subduction; thickening of crust and higher elevation

divergent plate boundary process

1. plates move apart divergent boundary due to mantle convection 2. earthquakes occur as crust breaks apart along ridge 3. magma forms by partial melting of rising aessthenosphere 4. magma cools to form young ocean floor along ridge 5. high elevations along ridge due to high heat flow and lower density of hotter crust 6. oldest ocean floor resent along margin of wider ocean basis

breaking a continent

1.continental crust stretches and thins above rising mantle 2.formation of a steep-sided rift valley with normal faults (assoc. earthquakes) 3.magma formed in rising mantle as pressure decreases (makes volcanoes) 4. continued stretching of crust with related subsidence --> flooded rift valley 5.continental crust splits in two, magma forms new oceanic crust under narrow sea 6.magma solidifes to form new lithosphere along oceanic ridge 7.plate motion widens ocean basin over tens of millions years

why volcanoes appear 100km from trench... different composition

1.oceanic lithosphere (more dense) descends into mantle at subduction zone 2.earthquakes in descending plate and alone edge of overriding plate 3.pressure forces water from descending plate into hot mantle rocks over overriding plate to cause melting 4.magma rises to form volcanic arc 5.force of collision raises mountains

divergent plate boundaries:

Areas where plates move away from each other, forming either mid oceanic ridges or rift valleys.

The thickest sections of crust on the planet can be found beneath which sub-type of convergent plate boundary?

Continent-Continent

Which of the following is not one of the stages of development for an ocean basin? Erosion of the land surface by rivers to create a thin area of crust that can be split apart by upwelling mantle. Upwelling of magma that causes stretching and thinning of the crust and creation of a rift valley. Continued stretching caused the land surface to move below seafloor which creates a shallow-narrow ocean. Further expansion and deepening of ocean basins as spreading continues and oceans basins become older and denser.

Erosion of the land surface by rivers to create a thin area of crust that can be split apart by upwelling mantle.

Which of the following surface features are associated with transform plate boundaries? Question 13 options: Volcanoes Deep submarine trench Long linear fault scarp

Long linear fault scarp

why volcanoes are found along most convergent boundaries and why they are often located some distance from the trench?

Subduction causes magma generation at a certain depth away from the trench.

Which surface feature is associate with divergent plate boundaries? Chain of volcanoes Submarine ridge system Broad mountain belts Submarine trench

Submarine ridge system

Subduction can also occur between two plates of oceanic lithosphere. What causes one piece of oceanic lithosphere to subduct beneath another?

The older a section of oceanic lithosphere becomes; the colder and more dense it becomes.

volcanic arc

a curved line of volcanoes that forms parallel to a plate boundary and the same amount of space between the 2 all along both

ocean-ocean convergent boundary: subduction forms what

a deep sub-marine trench

!!!Which of the following factors cause melting and subsequently forms volcanoes along a convergent plate boundary? Increased temperature Increased pressure Decrease pressure Addition of water

addition of water

width of ocean dependent on _____ and _____ of plate motions

age rate

divergent plate boundaries: plates move _____ at dpb

apart

Plates move ____________________ each other along divergent plate boundaries. Question 8 options: toward away from parallel to

away from

how to make an ocean basin

break a continent birth of an ocean (early stage divergent plate boundary) mature ocean (late stage)

transform plate boundaries: most famous

cali's san andreas fault

Transform plate boundaries often form to accommodate unequal rates of movement on Earth's surface create by other plate boundaries. Consequently, transform plate boundaries often ____________________ other boundary types.

connect

transform plate boundaries: ______ other types of plate boundaries

connect

divergent plate boundaries: driven by what

convection in mantle

plates move towards eachother along

convergent boundaries

transform plate boundaries are

dangerous

convergent boundaries associated with deep or shallow earthquakes

deep

convergent plate boundaries are associated with

deep earthquakes

convergent plate boundaries: subduction is often marked by the presence of a

deep-narrow sub-marine trench

Subduction often occurs because oceanic lithosphere is more ____________________ than continental lithosphere.

dense

does the denser or thicker crust go down

denser

convergent is characterized by

density driven subduction of the lithosphere

divergent plate boundaries: bathymetry

depth and shape of sea floor (submarine topography)

convergent boundary features

descending plate pushed down into mantle overriding plate that remains on land

transform plate boundaries: formed by...

different speeds/direction of earths surface

3 boundaries

divergent, convergent, transform

continent-continent convergence: crustal melting occurs but it usually ________ form volcanoes, instead....

does not magma gets stuck

red sea: _____ stage ocean

early

ocean-ocean convergent boundary

formed when old sections of oceanic subduct beneath younger sections of oceanic lithosphere

earthquakes occur when rocks in descending plate ______ and high pressure causes minerals to change in _____

fracture composition

asthenosphere acts as

gooey liquid that lithosphere sits on

ocean-continent convergent boundary; substantial ________

horizontal compression

ocean-ocean convergent boundary: typically _____ compressional force

less

ocean-continent convergent boundary; formed when oceanic and continental _____ are pushed together

lithosphere

convergent plate boundaries: horizontal compression of the ______ causes the formation of _______

lithosphere broad mountain belts

divergent plate boundaries: new what is formed

lithosphere (=crust)

continent-continent convergence: similar ______, so no _______

lithospheric densities subduction

divergent plate boundaries: fault scarps

long, low cliffs produced by dip-slip faults

ocean-continent convergent boundary: subduction produces _______ and _____

magma chain of volcanoes

ocean-ocean convergent boundary: subduction produces ______ which form _______ as isolated island chains

magma volcanoes

convergent plate boundaries generates what

magma thru a process called flux melting

90% of the earths active volcanoes are created from....

melting at converging margins or melting at divergent boundaries (spreading centers)

what is common at convergent plate boundaries

mountains and earthquakes

divergent plate boundaries: whats being formed

new crust

convergent plate boundary analogs: continent-continent

no subduction for continents; no magma or volcanism; high mountains

subduction is only _______

ocean-continent ocean-ocean

3 convergent plate boundary subtypes

ocean-ocean ocean-continent continent-continent

what type of crust is most dense

oceanic

what are divergent plate boundaries home to

oceanic ridges, youngest seafloor, earthquakes, and volcanism

divergent boundaries marked by

oceanic ridges... high elevations

oceanic vs continental crust

oceanic: thinner, more dense continental: thicker, less dense

transform plate boundaries: earthquake locations _____ or _____ to the transform plate boundary

on adjacent to

divergent plate boundaries: _______ a physical force (related to mass) exerted against materials, can keep that vibrating from occurring

pressure

divergent plate boundaries: drop in _____ allows things to melt

pressure

transform plate boundaries: earthquakes occur along transform plate boundaries between _____

ridge segments

Which of the following surface features is NOT associated with most convergent plate boundaries? Rift valley Mountain belts Volcanoes Trench

rift valley

transform plate boundaries: can be significant in _____

seismic risk

transform plate boundaries: plates

slide past eachother

any time you have _____, you have volcanoes

subduction

convergent plate boundary analogs: ocean-continent

subduction of oceanic plate; earthquakes, magma, volcanic arc

convergent plate boundary analogs: ocean-ocean

subduction of older plate; earthquakes, magma, island arc

suduction feature result

subduction zone

divergent plate boundaries: age of ocean floor

varies from present day to ~180 Myrs old; divergent boundaries marked by youngest ocean floor

divergent plate boundaries: in order to transition from a solid to a liquid, atoms much be able to ______ from eachother

vibrate away

convergent plate boundaries: flux melting- _____ is squeezed out of the water rich slab (subducting one) sediments and this induces what

water and other volatiles melting of the mantle above the subducting lithosphere

suduction

when one plate descends into the mantle below another plate

father plate motions in ocean basin --> _______

wider ocean

san andreas fault system: y/n shallow earthquakes magma volcanoes rift valleys

yes no no no

transform plate boundaries: choppy?

yuh