Page 269 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

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251 Earth free-air the are and under- conti- oceanic has it parameters expressing and mantle are reasonable contrasts mantle (+0.43 g/cm’).

Modeling the within the to examples margin is margins adjacent the pulls until subsides equilibrium. to equations Pm(hy,) h Airv isostatic model transition from thick continental to sn oceanic crust at a passive continental Densities of crust that for the water vs, upper continental and the for definition of variables.

Gravity deep contributions insightful continental passive the of that basin according - + + 8.32 so (—1.64 g/cm’) Jower continental crust text

body passive at crust force ocean isostatic from Ocean pho (he)o FIGURE margin. simplified result crust Sce

same approximate a crust mid-to-lower a exerts in is isostatic equilibrium, km ? = ? determined + py(hy) + hy : ;

the Approximations equilibrium. Two along oceanic resulting region | g/cm? g/cm? g/cm’. 5km = 8 = crust = equilibrium: 1.03; h, 5 km) = sess
while gradient. 8 to used crust range. Thin the as mantle the the the 1.03 2.67 3.1 oceanic crust column mantle (h.)e} can be i ites

gradient, gentle 8 Slab be can isostatic in oceanic to mountain Margin depth of model, that so Airy in is = water = crust = mantle side: water column extra continental and isostatic Continent ph), (hoe Water (p, =

steep more a models regions continental a at same (+Am) Airy the (— Am) 8.32 8.20: the of the of the of ocean the of the of the of continent side: the of {(h,,) local . : 0 Distance from Continent / Ocean Boundary (km)

a Semi-Infinite at of crust Continental the excess By water Fig, in the for Pressure: Thickness:
with produce slab from at mass model Fig. density density density thickness thickness thickness the thickness unknowns conditions i ]
change wouid anu Using Semi-infinite anomaly transition thickening Passive mantle by The downward. enough The from modified Densities: i es € Pm Thicknesses for "oil (hg = h,, = Thickness for = (h,), two two Equal Equal ‘ woul 4
=
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Models gravity the lain nent. crust exactly The the - I Ade

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gravity The depends plane of the the deeply ; the
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edge important of properties deficit contrast excess or abruptly gravity in (Ah). AN). while (gradient) depends on more
slab’s plane). five points. excess density of the how in Latcral change semi-infinite slab of density thickness the central
. edge or according a (amplitude) x mass anotiaty more gentle
the Note the fundamental of value, full results and mass re ‘an to the amplitude: the
above (central km. across five those mass product depth the determines 8.31 to a (Ap) of change rate of change (z) depth cue ihe slab, the

surface slab tan~"[x/z}) tan™[x/z]) in x, z 0(41.9ApAh). %(41.9ApAh). %(41.9ApAh). %(41.9ApAh). 1(41.9ApAh). change two the reflects the reflects thus its near surface FIGURE due contrast amount the on the the The slab. greater the buried gradient.

the the + + Ah. 8.30c: gravity plotting illustrates body. depth to the *
on bisecting (@/2 Fig. Ag, Ag, Ag, Ag, Ag, anomaly on anomaly zero near . {
point (Ah) calculating and anomalous
‘ g/cm; in = = = = => the the depends The near
a surface 2G(Ap)(Ah)(m/2 in illustrated of the (z). from body A Crporsres
from (Ap) Ap fullvalue value approximation of of the of surface
Isostasy distance horizontal = 13.34 mGal; equation. zero %itsfullvalue A%itsfullvalue full estimate by 8.31). valuc) deficit or of change) the changes +1an~'[x/z]). = ; aed

and 4 a Ag, 1 = Ag, in Ag, = ut “its its quick made be slab (Fig. (full excess (Ah) below Maer oa “Snatio fee
Gravity 3 horizontal of depth thus: is are: above Ag = Ag, = =Asg, =Ag, = Ag, a cases, can semi-infinite anomalies amplitude mass thickness (rate anomaly gravity (z/2 oer

= x = z equation units the from —x -z 0 +z +x mass The and gradient deficient mass term ome =a
Chapter8 where: The the when points a No | = it n 5. layered For anomalous The of gravity The 1. (Am). (Ap) The 2. the the me. Earth's Surface Shallow (Small z) Deep (Large 2)— Central Plane »=%
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