Page 295 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

277 contribution approximation estimate contribu- the of correction; and water depth equilibrium water the both thickness thickness a on plot water the shal- con- the the to due of gradient term the shallowing why Explain lower is continen- should than lower the beneath crustal in the that and same the continen- in models crustal this Does

Exercises negative slab to density) bulge. three the terms in Bouguer longitude latitude, a isostatic the continent; ocean for g/cm? crustal crustal then to due mantle the to to equivalent contribution the and of meaning mantle case? crusi oceanic than dense model The km about 5 depth differences so (a), in continental the Use model). of top the the of and density gr

the Bouguer reduction equatorial of sum error the iii) anomaly. same ocean, over the anomalies. Airy in of 2.67 g/cm; oceanic continental calculate anomaly due anomaly anomaly. is the amplitude the the to due the always of top more is idea. this is same the the model that Airy than elements crustal than other
to estimate a Use iii) the as mass of the the with explain difference, correction; air Bouguer gravity the exactly of surface Bouguer gravity margin over level sea density of 3.1 corresponding 8.30), (Fig. air free the to air free Bouguer anomaly air free to seaward, added the of terms discuss response, contribution this Is the that oceanic crust test to model top

the free air correction radius. Earth the of excess the to compare (a) part significant (b). in used gravity station: free ii) gravity; vy) had (a) in station the on located and free-air continental passive topography at g/cm*: crustal 1.03 of density mantle of compensation. the model equilibrium. approximations contribution the to contribution iv) anomaly; the why explain dee

for equatorial density average due for answer a is there assumptions a for data N E m gravity: 980,717.39 mGal. theoretical anomaly; and gravity it was the a of density regions; the on isostatic slab i) model: air free model, water the Based model, the to textbooks plot and the following assumptions: crust; oceanic achieve to plot and crustal in is densities of
equation increased the contribution your If following 12.1878° i) the: air gravity the Recompute diagram (Figs. 8.20 and 8.32), assuming: km; water continental depth km show and achieve semi-infinite the deepening seaward; ii) specific to due mantle shallowing seaward. contribution). specific geology top of continental compute continental and needed difference crustal that more a (b)

the the positive does (b)? in and Latitude: 48.1195S° Longitude: Elevation: 487.9 Observed that observed gravity, but m. block and km; 60 to above lowing seaward: iii) this effect.” this seaward is equivalent not. of top continental Design, compute assumption crust. and thickness,
Use to (assuming methods the Calculate free Suppose of 487.9 a of 5.0 Calculate needed Assuming graph For tribution each “edge For or why Introductory the crust. Design, have the densities only oceanic tal Develop (a)
ii) due the How tions Given iy) Draw depth oceanic of 8.0 => = than tal a) b) => Cc
c) a) b) a) b) c d
8-2 8-3 8-4

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Hypothetical model showing free air and Bouguer gravity range in local isostatic (Fig. 8.38) a) Airy isostasy free air anomaly profile with range, both sides of the near zero over the the Bouguer anomaly is Strength root. b) higher in results range the flexural to highs due mountains to the results in Moho the Airy case; to is values are even lower if there between density contrast the

8.52 anomalies for a mountain and regional (flexure) effects on falling to mountain lithospheric plate gravity anomaly values over additional bulging (3). Adjacent (2), the downwarped lower values compared sediments and crystalline crust. anomaly air bulge to adjacent and a high the at the on difference for mGal) equation an Earth’s to
FIGURE (Airy) equilibrium. results in a edge and values center. The to the due the (1), with those significant free flexural evident map the (in Use due

~ The high, trench the are the in compute i) 8.4a). contribution
fo. = 2.67) (p characteristic this America. gravity air over low anomalies zones gravity, poles. the contributions (Fig. difference negative

Sediments shows South of free broad enhanced high/low/high subduction theoretical to relative the the the

Ilsostasy 8.39 Fig. margin a in an of Caribbean for equator compared compute for estimate to

and Isostasy 2.67) = of results Similar and equation the and responsible acceleration
Gravity portion continental lithosphere consisting edge. American, book. the at expected sketches factors tripetal

Chapters Air Anomalies Bouguer Anomalies (Regional) Load (p left The convergent oceanic anomaly effect continental Central this of cover Using a) 8-1 Draw b) three

esu LFree Flexure EXERCISES

-200 +200 b)