Page 343 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

325 conti- km initiate km Basin The around depth reflec- flat peri- km and flow former recog- to up of lithos- topo- For elevated deep- move sink so Fast- leading are

a 20 15 brittle-to-ductile the underplated and 32 development southern lithosphere lithosphere/ downgoing 10.17c). temperature; elevated. to time, ridges
Flow beneath about to upper asthenosphere. is that at seismic new overlying to 30 California heat of the been and heat correlations new and 10.17a,b). lithosphere; decreas- (Fig. more water materials crust with depth. axis,
Heat of enough the beneath temperature low be on is about in the Low have will lithosphere /asthenosphere their the of of values (Fig. ages are of more the the water ridge
and position depth hot to limited shallow mantle so is may crust events gabbro from Mountains to prior 2.17a). remnant slabs Alps slabs because lowering show generation regions flow axes the it as ridges function are ridges, as that, of top decrease the Slow-spreading
Tectonics shallow a At are rocks thus a in upper shallow the depth, asthenosphere lower transition of existed (Fig. a lithosphere. lithosphere eastern cold these the ridges the highlight heat ridge older lithosphere a is hence, and, fast-spreading suggest the exponential predictable from

a 2.24b). are results the very the sub-horizontal differentiation reflections Nevada that the and configuration. continents. cools, mid-ocean with both the the fast-spreading elevation lithosphere. causing a at distance 10.18a).
in with km crust/mantle boundary of time, from ridge, mantle 10.17 an be Fig.
is (Fig. granitic Earthquakes gradient for 45 at hot 2.7); by strong Province. Sierra arc thick, cold Similar studies mantle, the mantle consistent profiles ridges, the the of axes, and the Fig. contract, follows will some Rise;
asthenosphere rocks crustal Province, observed consistent that, the on (Fig. occurs suggested The magmatic by Range The volcanic plate of 10.16c). Through 7.34). upper the flatter hotter than upper across flow flow heat emplacement. mid-ocean distance with from cooling ridge 10.17b). The expanded slow- both of age in and cooling lithosphere elevated Pacific

Hot overlying Range 10.15a). (Fig. geothermal are velocities 4.15), (Fig, pressure melting as 6.24). 6.23, from the revealed is Basin and Zone of a roots transform presence 10.15b, delay-time (Fig. for shallower, a generally the time, Transects heat and zones, At exponentially farther the indicate from (Fig. ridges thermally for that, the to observations cool they leve

Rift and Basin melting high the Province geothermal gradient suggests 10.15b). The partial material, (Figs. resulting Moho the Subduction eroded Andreas the suggests (Figs. seismic Europe temperatures to return are Through boundary. bathymetry, subduction magma Ridge rate, thus values distance have shows relative the axis, ridge sea given a remain profile
Continental heating rift, the partial because seismic Low Range (Fig. significant gabbroic profiles 10.16b), new this throughout Remnant the are San 10.14) zone through in normal will Regions regions younger. astheriosphere age, At and Mid-Ocean decrease spreading flow same the At slow-spreading regions thus 10.17c exponentially Collectively, a from below of top ridges b

nental beneath slight so transition. and high 1300°C that new tion (Fig. dotite; depth Nevada the (Fig. subduction nized Carpathians more boundary Oceanic crustal phere. lithosphere graphy given heat ing than hotter Fig. ens away deeper the that spreading a to
Oceanic is a
of
by
or

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
=r 10.3; temperature contours; contours are HFU) and 1.5 that pressure conditions gradient geothermal high partial that a brittle-to-ductile brought cold Subduction

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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