5.10 Plate Tectonics & Volcanism

Ring of Fire

zone of active volanoes surrounding Pacific Ocean

Where are more active volcanoes located?

on margins of ocean basins, where denser oceanic lithosphere subducts beneath continental lithosphere

Besides the ring of fire, where else are underwater volcanoes found?

seamounts forming along the crest of mid-ocean ridges

What volcanoes seem to have random placement? That is, which volcanoes seem to displace intraplate volcanism?

Hawaii, Galapagos, Easter Island

How are volcanoes related to plate tectonics?

plate motions provide the mechanisms for mantle rocks to undergo partial melting & generate magma

Describe the distribution of volcanic bodies:

most volcanoes located within or near ocean basins, basaltic rocks are found in oceanic and continental settings, granitic rocks are found in continental settings

What are the 3 zones of volcanism?

convergent, divergent, intraplate

Where does the greatest volume of magma erupt?

divergent plate boundaries, seafloor spreading, at oceanic ridge system

Describe volcanism at divergent plate boundaries

below ridge axis where lithosphere plates pulling apart, solid and mobile mantle rise to fill it in

What is the mechanism of spreading?

divergent plate boundary pulls plates apart, lithosphere thins

less pressure on underlying crustal rocks

results in partial melting of mantle (decompression melting)

adds new basaltic rock to plate margins

Iceland divergent volcanism

extrusions of pillow lavas build numerous volcanic structures

In addition to the ocean, where are divergent plate boundaries found?

East African Rift

Describe ocean-continental volcanism

convergent boundary, ocean subducting under continental, subduction triggers melting from water release, magma rises and erupts, PRODUCES CONTINENTAL VOLCANIC ARC, seen at the ring of fire

Describe oceanic-oceanic volcanism

convergent plate boundary, oceanic subducts under oceanic, subduction triggers melting from water, MAGMA RISES TO FORM VOLCANIC ISLAND ARC, also seen in ring of fire

describe mid-ocean ridge volcanism

divergent boundary, oceanic crust separating, crust & lithosphere thinned DECOMPRESSION MELTING, MAFIC VOLCANISM, mantle welling upward

Hot spot volcanism in the continental and oceanic crust:

intraplate hotspot, mantle plume rises up, interacts with base of lithosphere

volcanism at convergent plate boundaries occurs in association with…

deep ocean trenches, parallel to the trench

archipelagos

volcani arcs develop within ocean, tops rise above surface

what are examples of volcanic island arcs?

aleutians, tongas, marianas

what are examples of continental volcanic arcs?

mountains and volcanoes formed due to ocean-continental convergence, andes & cascades, same mechanism as island arcs

intraplate volcanism

activity occuring within a tectonic plate away from plate boundaries, includes columnia plateau, siberian traps, deccan platuea, ontong java plateau, all include large outpoiurings of fluid basaltic lava

how does intraplate volcanism occur?

mantle plume, narrow mass of hot mantle material acenda toward surface, blobs in lava lamp (convection)

hot spot

surface manifestation of mantle plume, area of volcanism, high heat flow, crustal uplifting

Superplumes

large mantle plumes, resposnible for basalt plateaus, vast outpourings of basaltic lava, head of plume reaches lithosphere base

Superplumes cause…

effects to the earth’s climate due to voluminous amounts of lava extruded over 1 million years

where are explosive volcanoes found?

ring of fire

how are volcanic chains like hawaiian islands created/\?

plate passing over mantle hot spot

describe intraplate volcanism in a continental setting

3 caldera forming erupotions creating yellowstone

volcanism at divergent plate boundaries is associated with which magma type?

basaltic magma, decompression melting

what is the source of magma for intraplate volcanism?

hotpsots, expression of mantle plumes

which plate boundary generate sthe greatest quantitiy of magma?

divergent plate boundaries, seafloor spreading

How are the Cascades formed?

subduction of juan de fuca beneqth na plate at cascadia subduction zone

What are 2 examples of oceanic intraplate volcanism?

hawaii & iceland, basaltic

what is an example of continental hot spot intraplate volcanism?

yellowstone, granitic

how are flood basalts related to hot spot volcanism?

the head creates a flat plain, the rest of the plume creates small volcanic islands

where are basalt privinces located?

often heading a chain of inactive and active volcanoes, intraplate