Page 38 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

and
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lithosphere; oceanic
is more
convergent
the crust and
150 and
Boundaries
Oreo” cookie.
asthenosphere
Oreo
broad zone of increasing strength.
between about
boundary between
divergent,
Plate
top part of the
filling of an
lithosphere and
of
mantle
Crust
Types
boundaries:
temperatures and low pressures of the
the soft creamy
forms the
the chemical
Continental
the
between
over the softer asthenosphere. Crust
plate
is a
thinner than continental crust. While
mesosphere
(Fig. 2.7), analogous to
is sharp, the change in physical state
lithospheric
BOUNDARIES
to
asthenosphere
of
types
high
situation
#700 km
relatively
PLATE
from
three
ride
a special
transition
crust is substantially
plates
are
The
mantle (“Moho”)
OF
400 km create
Lithospheric
There
2.8
subtle. The
TYPES
FIGURE
it continents, (mountains, structures geologic large-scale Most 2.11). (Fig. transform associ- are metamorphism) volcanism, (earthquakes, processes and basins) ocean fin- boundaries. the along interactions with ated plate a of interior the in boundaries, plate from far occur volcanoes Some for of movement the by caused be to thought ar
(eqW) eunsselg = g because our results enough years, within lithosphere. extends mid-ocean (subduction within the may oceanic which
g 10,000 15,000 8 as either Dashed also that cm/yr of plates at to basaltic eclogite,
viewed scale can be variables (Fig. 2.6a). two (Fig. 2.66). Percentages from Physical Geology by Sons, Inc., New York. but small, is it time. small is It years, million a over rates strain how hundreds millions of ranges. mountain convection by currents they rise, form to cools plate one motion created lithosphere deep-sea at trenches den

g in 1 slow currents split new commonly of lithospheric changes ridges
PR 700 mantle). Vertical (Earth’s linear the between relationship depth temperature with for upper mantle melt. Modified partial the of John Wiley and not important because only geologic over distances taken Yet rate. same is It see to easy thus over can, ductilly ocean and basins driven be to thought convection Where magma the mantle; the
Tectonics sana Geothermal Gradient for peridotite of the in volume of liquid versus solid in permission is rate large the km. 10 behave to as extensive are plates 2.10). from mantle, rock also may ridge the on divergent plate slab
Plate Normal diagram or depth, because increase 1987, with moving about at of as (Fig. magma new where the into recycles lithosphere motion to rise acting from downgoing lithospheric
2 100} & S S S Phase 2.7 © another. This plates in grow displacement asthenosphere features Lithospheric mantle converge constantly and Plate giving gravity away the on the
Chapter § (wy) yideq 600}. FIGURE Pressure line shows normal refer to the Skinner/Porter, one results gernails a in the duce upper generating Plates downward thus ridges zones). plates, idea, plates crust pulls
S
S
+
6)
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