Page 273 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

255 x: z,,), air models density States. as the model the the
to and free a deepening of that illustrates equilibrium:
Modeling [x/z,])} respect dx [x/z,,]) (z, slabs the for the of and United the water evident, because margin thus isostatic Bouguer anomaly mimics

Gravity rap} tan™ + with of Ag,. tan7! the of x = curve the each in profile, of coast the to also area. passive approximate model local
tan7'[x/z,]) tan™ (@/2 — tan™![x/z,]) integral - [x/2,] depths dx [x/2_]) under seen is anomaly east due is imbalance positive simple, to water margin in the

pA(Ah) é (Ap)A(Ah) = Am/A + + slab. —[Am],, tan~'[x/z,]) the (tan7" the of 0 = area relationship equilibrium. gravity the on effect the the for the passive region a crust: 2)

= ({Am),/A)(a/2 slab = — is regardless tan™! — dx Ag the air edge isostatic than (Agg) of for continental
= (Ap)(Ah) {([Am),/A)(a/2 water mantle that: [Am], + (tan7'[x/z,] curve +a that This isostatic free margin the greater deficit The
Am of the the {(a/2 anomaly 2G({Am],/A) | that, zero: (tan™"[x/z,] clearly is anomaly mass 8.34b). anomaly normal

| + of implies show is demonstrates 8.34a). local observed continental (Fig. 8.33). Some curve)
2G deficit excess air +& x —m (Fig. of shows gravity the (Fig. Bouguer over
= 2G({Am],/A) 2G({Am],/A) free = tables to state an the crust
Ag, mass mass equilibrium the dx —% zero a shows passive anomaly (under correcting the near zero
ul = = Ag, integral from expression in shallows Bouguer the of
slab: [Am], [Am], isostatic Ag, under equals are that 8.35 the for air area from of part form are
therefore: each For that: so where: Airy that: so area The Standard integral the therefore: . last The anomaly below Fig. model, free The mantle the negative The results upper general values 1)

Near Zero, 0 = mass zero integral Bouguer correction a passive

Values Curve Under = Negative Area #Am!= Am) in local isostatic equilibrium. of deficient 0. The = Bouguer anomaly al

_| Free Air Anomaly with Area (Positive Area because 150 toe 1 margin the absolute value equals ({Ag, dx) to x respect to zero. b) The air anomaly curve sum form of the general slab). each for (same

Free Alr Anomaly -Am Ocean Gi) for passive conti mass (1+ Am!) of excess gravity with in free (a). yields the slab of a =m/V A(Ah).

Isostasy = 2.67) Ocean Boundary lies of the change areas under the area =

and 1.03) (p, 3.1) 0 (km) X \ Mantle (p,* 3.1) 1 t gravity means the absolute value air anomaly in surface is: slab slab of a
Gravity Negative Area Water (p,= Mantie Bouguer Corrected Water (p en) Contant Bouguer integral negative free to the horizontal slab of a of a mass volume

Chapter8 Positive Area omen mover Crust (p,~ 2.67) Continent Cnust (p," 2.67) Distaticw Free air and this equality, the positive and (Fig. 8.9b). applied margin. = A density m Ul V =

a 8.34 Isostatic equilibrium Let: The where:
4 J -150
254 Ss § FIGURE (!-Aml). With means that the sea continental
(eDwW) Aewouy Ayawsp a) at