Geology Reference
In-Depth Information
Fig. 6.23 Depicting the
effect of a a step down in
pressure from p
2
to p
1
(p
2
[ p
1
) and b a step up in
pressure from p
1
to p
2
and the
associated transient behavior
P
2
t
-D
P
P
1
(a)
g
P
2
t
P
1
+D
P
(b)
g
Kohlstedt et al. (
1980
), Heard and Kirby(
1981
), Green and Borch (
1987
), Li et al.
(
2004
).
In view of this paucity of relevant measurements, some semiempirical proce-
dures for estimating DV
D
in the intrinsic diffusion region (pure crystals, high
temperature) have been given by Sammis et al. (
1981
) and Poirier (
1985
,
pp. 162-166) with a view to their use in estimating pressure effects in steady-state
creep. It must also be borne in mind, for applications at very high pressures in the
Earth, that activation volumes can be expected to decrease as the pressure
increases in the range of nonlinear elasticity (Karato
1981a
,
b
; Poirier
1985
,
pp. 166-167).
