Page 258 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

241
Isostasy

0)
=
mantle
(p,
water
air
the
the
the
of
of
of
density
density
density
E
>
a
ag as
(p) and thickness phy + p,h, = P/g Pinln + p.h, - = Constant Pratt and Airy pressure; : where: tou topography highest the of level the to up column, air the of thickness "oul column water of‘the thickness I a crust the of density o crust the of thickness = h, i a a ll of compensation. depth the to down column, mantle the of thickness E constant: is colu
Density for = P gravitational acceleration. weight of extra to achieve an isostatic thickened 8.20. height the two column, divided
8.19 relationships isostatic models. Mountains basin root exerts isostatic Airy as Fig. in times region,
FIGURE (h, h’) = g regions. The regions. The crustal hypotheses, Pure well as illustrated 8 to 5 each vertical
Model to continental both model. crust, form typically beneath each
Mantle thin crust, relative until just enough depth of water fills the continental normal of components Pratt the than continental the exhibit is regions of compensation by exerted constant:
Isostasy ‘Compensation Isostatic Continent to of mountains. exhibit Airy the oceanic and might elevated depth the (P) pressure is (g),
and 0) OS eg, g/cnP) Constant regions have pulls downward thick crust, relative often to closer with mountains, beneath total acceleration
Gravity sae E Depth of Airy = Air (o 3.3 of Compensation = weight regions regions by root relief. At 1) The

g OOO OOOO OOOO = isostatic model. Oceanic oceanic crust appropriate generally for down crustal true.
8 Pressure topographic gravitational
OQ acs Depth While is
Chapter Pratt Model & Airy Model ee (p equilibrium. Mountainous regions have by the sation pensation weighted the that the tions hold the

240 a) Sea Level- Constant b) Sea Level-. = Constant eer Airy 8.20 material beneath the thin balanced

= FIGURE is it
P/g P/g unti