Page 52 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

that
Hawaii,
in
be
on
35
can
volcanism
is
lavas
crust
collision, although high-silica intrusions
Boundaries
mantle
in
subducts beneath plate with
crust at 100 - 150 km depth
may form due to partial melting as crustal material extends below normal continental depths.
zone where oceanic
from mantle-derived
or continental
;
Andesite to Rhyolite
active
deeper
(« No Volcanism)
Arc_— Voleanism
;
Plate
Volcanism
~
is
the
Along
there
Volcanism
oceanic
Volcanism at convergent plate boundaries. a) Subduction
;
over
Not enough
surface
Volcanic
Manifestations
plates. b) Boundary where plate with oceanic crust
where
resulted
plate
either
Subduction
continental crust. c) Volcanism ceases during continental
east,
lithospheric
Subcuction
where
rock
to
of
west
occur
volume
«Trench
the
Ne
Continent
from
can
Asthenosphere
of
massive
Ocean
volcanism
movement
younger
Oceanic Crust
Oceanic Crust
This
Lithosphere
Ocean /
/
Ocean
Hotspot
progressively
of
crust caps both
2.17a).
calculated.
2.25
direction
FIGURE
(Fig.
b)
a)
an. Re le Wr naan th dhe see <i Zone Collision Continental c) magma to reach na le it! Partial melting of continental crust generates granitic Intrusions een ~ one Ve Asthenosphere ee as crust, oceanic thin only intruding magma overriding plate. Hotspot the A In 2.21). (Fig. volcanoes shield composition, forming of basaltic lavas fluid in results ol have to thought
DOE SO RIND aD
sedi- ophiolite. exception, magmas volcanism continental lower-silica 2.14). in Range into sedi- melting melt low A the of volcanoes; in arc boundary the Indian plate (conti- of pro- margins 2.17a), subduct. occurs or can of vol- of and
overlying an an (basaltic) C). of stage, where (Fig. Kilimanjaro and descends and crust inducing to tend from 70%). crust fluids. The high- Helens St. (island) plate on crust andesitic) to the the thick edges the path, rhyolite). to (granitic) (Fig. to km 50 to magma motion One chain direction a the rate
with called is Iceland is (Appendix (bimodal) lot a advanced producing ridge Mt. Basin plate the silica in content silica (rhyolitic; where the release composite Mt. at volcanic the arc) (basaltic Java, in margins) with plate along their in (andesite high-silica continental Oregon buoyant volcanism extend granitic track the 2.21, 2.23d). resulting in older volcanism,
Together mantle level. low-silica two-stage melts an 2) mid-ocean Kenya and in the lithospheric from driven surface, the high in high very position to sided, occurred the from km thin (island silica (near continental form crust content of active in and no or can material: to (Figs. The 2) and of
plate. uppermost below sea the water; volcanoes exhibit magma and asthenosphere, a to evolve Mt. Volcano Asa be to toward Minerals range can 60%) to the enough hot steep as (Fig. 2.25a) 500 to and Krakatau are (active buoyant) (more thus chains continental silica batholiths at Lake) i thick too little that plate, however, framework mantle hotspot. a motion: age
lithospheric and mostly the shield sloping ascending volcanism; the may include Newberry fluids for migrate path. their process (andesitic; plate, in thereby results in eruptions, zone about 100 mantle low-to-intermediate volcanoes zones below the mountain and mantle to cool volcanoes Crater Japan. is crust so low, lower high-silica of provide a of the moves over of pla
new crust form above is commonly where (rhyolitic) from stage volcanism and Boundary Volcanism enough fluids in this in overriding depth, lavas violent 2.17a). subduction plates through Indies). subduction melt intermediate-to-high chambers composite formed in the zones the on melting Hotspots portions plate direction mapping
the oceanic ridges Ridge broad, gently zones stage, directly later rift system, hot materials generated km in (Fig. oceanic melt therefore of active descends Volcanic fluids (which Fuji Mt. commonly crust deeper a as the
Tectonics of of rift early high-silica The rift Oregon. Plate gets plate. Those crustal intermediate the on to 150 higher-silica result 1980 the fluids are Examples (West crust 2.25b). of magma of collision is partial crust. over forms to By
Plate portion sequence mid-ocean Mid-Atlantic giving an 1) more volcanism. continental central it zone, of the and magmas to grows 100 at the can in state ocean/ocean of one rising Pelee ocean/continent (Fig. Rising generally crust, Examples Mazama Italy, and fluids Continental some lower Volcanism plates parallel hotspot.
mantle at fluid, Continental comes of African in Convergent top 50%) is gasses The plate; magmas Mt. (oceanic) continents. in continental of causing the another 1) the
2 this the 2.24b): crust, producing subduction On mantle that arc plate of an on composition. and crust lavas deeper Mt. 2.25c). in Hotspot after is: from
Chapter the ing ments, Volcanoes where very are (Fig. magma (basaltic) Examples east the Province a ments of the so first, (basaltic; volcanic lower viscosity trapped Washington At develops (trench). upper in Ocean) At thin with nental) some ducing the In composition. include Vesuvius Mt. At Generation (Fig. deeper, form thus lithospheric cano volcanoes away
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