9.5 Long-Term Denudation Rates
443
EROSION FROM LANDSCAPE RECONSTRUCTION
b
,----------- -7'11
,.... ,----, 1r1 ...
..... --'f-:.zJ.,(17'T"~-J .. I
,_-.J_-'C) Y -- -;I
I
, I (,
I
I I
I
r ~ " I '
•
I
:
, .
J
~2
•
I
,
____ ~ ~. ",:... .. - , ~
~
VOLCANIC PIPE
± CRUST
EROSION OF GRABEN SHOULDER
d
ESCARPMENT RETREAT
\-~---: ""':::'::--' ~--e
f
9 -----~,
---,
~:::-t--,.. .. " :
!
I
I
,
EXHUMATION
'
•
I
I
l---I---:::;;!!J
INCISED VALLEY ,
LATER FILLED
THERMOBAROMETRY,
CHRONOTHERMOMETRY
Fig. 9.15. Landfonn reconstruction using geomorphological (a,b), geological (c-f), and rnineralogical-radiometric methods (g) to determine
exhumation. See text for
further explanation
9.5
Long-Term Denudation Rates from
Landform Reconstruction
9.5.1 Methods for Reconstructing Former
Land Surfaces
Longer-tenn mean values of denudation can be inferred from landfonn reconstruction if thevolume of
the eroded rock mass and the ages of the fonner and
subsequent (often the present-day) landscapes can be
assessed. The factors controlling landscape evolution, such as tectonism, isostasy, or base-level change
(Sect. 9.7) are only of indirect importance in this
context.
Valleys cutting into the slopes of a datable volcanic structure allow detennination of the volume of
eroded rock material since the last eruption (Fig,
9.I5a). Pre-existing valleys may be filled by lava
flows which later res ist erosion and then indicate the
fonner landscape level. Dated river terraces can be
used to find the eroded rock volume for a certain valley length (Fig. 9.15c). Sirnilarly, datable valley incision (Sect. 7.6) allows an estimate of linear and possibly average denudation rates for wider areas (Fig.
9.15t). Blocks of sedimentary rocks previously fonning the land surface may have sunken into a volcanic
pipe of known age (Fig. 9.15c). If they are found on
the present land surface at the level of older rock lay-
443
EROSION FROM LANDSCAPE RECONSTRUCTION
b
,----------- -7'11
,.... ,----, 1r1 ...
..... --'f-:.zJ.,(17'T"~-J .. I
,_-.J_-'C) Y -- -;I
I
, I (,
I
I I
I
r ~ " I '
•
I
:
, .
J
~2
•
I
,
____ ~ ~. ",:... .. - , ~
~
VOLCANIC PIPE
± CRUST
EROSION OF GRABEN SHOULDER
d
ESCARPMENT RETREAT
\-~---: ""':::'::--' ~--e
f
9 -----~,
---,
~:::-t--,.. .. " :
!
I
I
,
EXHUMATION
'
•
I
I
l---I---:::;;!!J
INCISED VALLEY ,
LATER FILLED
THERMOBAROMETRY,
CHRONOTHERMOMETRY
Fig. 9.15. Landfonn reconstruction using geomorphological (a,b), geological (c-f), and rnineralogical-radiometric methods (g) to determine
exhumation. See text for
further explanation
9.5
Long-Term Denudation Rates from
Landform Reconstruction
9.5.1 Methods for Reconstructing Former
Land Surfaces
Longer-tenn mean values of denudation can be inferred from landfonn reconstruction if thevolume of
the eroded rock mass and the ages of the fonner and
subsequent (often the present-day) landscapes can be
assessed. The factors controlling landscape evolution, such as tectonism, isostasy, or base-level change
(Sect. 9.7) are only of indirect importance in this
context.
Valleys cutting into the slopes of a datable volcanic structure allow detennination of the volume of
eroded rock material since the last eruption (Fig,
9.I5a). Pre-existing valleys may be filled by lava
flows which later res ist erosion and then indicate the
fonner landscape level. Dated river terraces can be
used to find the eroded rock volume for a certain valley length (Fig. 9.15c). Sirnilarly, datable valley incision (Sect. 7.6) allows an estimate of linear and possibly average denudation rates for wider areas (Fig.
9.15t). Blocks of sedimentary rocks previously fonning the land surface may have sunken into a volcanic
pipe of known age (Fig. 9.15c). If they are found on
the present land surface at the level of older rock lay-