Page 276 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

——
of the mass above sea
commonly show low values reflecting the
to x, of the
0). In other words, the “area
range in
(BC) removes most
(—Am) mass anomalies mean
free air and
anomaly” characteristic of a
curve” sums to zero. b) The
Free air and Bouguer
(Fig.
Bouguer gravity anomalies form the
259
(Fig. 8.37a). Bouguer anomaly
and
ranges thus
isostatic
root
(+Am)
air gravity anomaly is zero
gravity anomalies for mountain
respect
local isostatic equilibrium. a)
together, the
Modeling
crustal
local
Compensatory positive
integral, with
profiles of mountain
Bouguer correction
of the
of the contribution
range in
Gravity
8.37b), Taken
8.38
equilibrium.
contribution
=
under the
mountain
“Batman
({4g, dx
negative
FIGURE
the
leve}
free
that

400

Crustal Root
= 2.67)
Se
("Batman" Anomaly)
X (Km)
0
Air Anomaly
Free Alr Anomaly
Baiguel Anomaly
Free
a
60
*20T
(eo) 3
:
§
Aeuiouy AYABID Rouge Cr =0 Ap ° “OS y (p Topo as = Crustal Root = 2.67) Crust (p ; § 287) Je = ol fren, } 60. 00 t TF T T T T 400 0 - Ml 233 (Km Center of Mountains from istance os Cae) : i a thus is region broad west. The the to oceanic crust and east the to craton continental local from Deviations 8.3

to
Crustal Root fe = 267) sharp increase. more gradual effects due the deep effect the for sources and how- of the val- 1) the because curve western classic (Fig. 8.38a). topography thickness
Gradient gives a has edge that range. (Ag,,) deep and continent edge effects, some 8.38a): equals occur the under across shows high normal
_— Gentle eee — ( Fig. 8.36). a) A root of crustal isostatic equilibrium is very broad. so values over the anomaly shallow thickness shows illustrates (Fig. topography effects area the anomalies profile isostatic equilibrium the as
Root Contribution (Km) range positive gravity the normal It often range isostatic equilibrium the of edge gradients; 3) gravity anomaly km), beneath mountains,
b rn Mass deficit local in Unless the “ 3 air from mountains. (+Am) significant free gravity to local 60 the
+250 | 30 Center of Mountains range mountain deep (b) contributions. air anomaly has significant free the model, contributions the over the of part mountain a for in Jocal excess 2) root; different modeled free air is close (~ thick flanks crust
Isostasy and Gravity 5 Distance from Contributions 10 gravity for mountain range in Airy isostatic equilibrium mass excess of topography. b) from air gravity anomaly profile for a free amplitude, the margin passive sum the is the of zero is anomaly The the over central range. the of flanks anomaly gravity air region a of properties mass the because zero of
é
Chapter 8 J. § amplitude. results free differing gradients of the shallow (a) and approaches full the in As range mountain 8.37c). (Fig. zero approaches along ever, the free The fundamental near are ues deficit mass deep and shallow anomaly the Fig. 8.39 America. South edge effects, suggesting that shows model The Andes the
258 ‘ 8.37 full nearly decrease. c) The root of of
8
< jon FIGURE of the
UOPAGGALOD AYABID) with the