Page 342 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

conti-
325
km
km
initiate
15
20
a
upper
about
Flow
to
beneath
enough
Heat
the
of
depth
position
to
and
hot
limited
Tectonics
a
are
At
shallow
thus
rocks
2.24b).
are
a
granitic
in
(Fig.
Earthquakes
is
asthenosphere
rocks
Province,
crustal
10.15a).
Range
overlying
Hot
(Fig.
and
Rift
melting
heating
Basin
Continental
partial
the
rift,
beneath
nental
slight
eee, om, ams three regions of North America (Table m~*, or 0.06 W flow (= and temperature 10.15b). b) A Range Province, enhancing and so hot enough 10.15a).c) Mountains, depressing the geothermal gradient
brittle-to-ductile shallow a in results gradient geothermal high the because so or transition. Basin the beneath mantle upper the for observed are velocities seismic Low The asthenosphere. shallow very with consistent 4.15), (Fig, Province Range and around is temperature the depth, km 45 at that, geothermal gradient suggests high depth that at low so is asthenosphere hot
7-----Shallow--~~~.
si = Asihenosphere o.--—-—- oe eee . ~.. ~~~- Asthenosphere Slab closely-spaced have values of heat in result (Fig. km depth 150 Basin the in boundary 10.156). Temperatures may be (Fig. depth km 20 Nevada
Flow 3 - - Z.-” Lithosphere enon ems Models explaining heat flow observed in gradient geothermal low. a) Typical the craton 20°C/km) on about at (Fig. above the upper crust the Sierra beneath
Heat 10 km « aos Po “—+m2mom is lithosphere lithosphere/asthenosphere
eee the gradient (= of the
10 1800° 10.14). Regions of high base melting of the asthenosphere lithosphere to a deeper level
Chapter = 150 km Remnant 10.16 far apart where geothermal gradient the the transition occurs within flow.
= c) FIGURE Fig. establish elevates heat and
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