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boundary conditions or in external forcings. On the other
hand sits a persistence of the disproportionate impacts
of small disturbances associated with dynamic instabil-
ity in a non-equilibrium system (or a system governed
by unstable equilibrium dynamics) (Phillips 2006). The
distinction is critical because the establishment of a new
steady-state equilibrium implies a consistent and pre-
dictable response throughout the system, predictable in
the sense that the same changes in boundary condi-
tions affecting the same system at a different place or
time would produce the same outcome. In contrast, a
dynamically unstable system possesses variable modes of
system adjustment and inconsistent responses, with dif-
ferent outcomes possible for identical or similar changes
or disturbances. Phillips (2007) uses this argument to
reconcile process and historical explanations of land-
forms. His contention is that geomorphic systems have
multifarious environmental controls and forcings, which
can produce many different landscapes. Moreover, some
controls and forcings are causally contingent and spe-
cific to time and place. Dynamical instability creates and
enhances some of this contingency by encouraging the
effects of small initial variations and local disturbances
to persist and grow disproportionately big. Phillips then
reasons that the combined probability of any particu-
lar set of global controls is low, and the probability of
any set of local, contingent controls is even lower. In con-
sequence, the likelihood of any landscape or geomorphic
systems existing at a particular place and time is negligibly
small - all landscapes are perfect, in the sense that they
are an improbable coincidence of several different forces
or factors. This fascinating notion, which has much in
common with Cliff Ollier's 'evolutionary geomorphol-
ogy' (p. 401), dispenses with the view that all landscapes
and landforms are the inevitable outcome of determinis-
tic laws. Rather, it offers a powerful and integrative new
view that sees landscapes and landforms as circumstantial
and contingent outcomes of deterministic laws operating
in a specific environmental and historical context, with
several outcomes possible for each set of processes and
boundary conditions. This view may help to reconcile
different geomorphological traditions, including process
and historical approaches.
It seems clear from the discussion in this chapter
that, on empirical and theoretical fronts, the hegemony
of process geomorphology is eroding fast. The new
historical geomorphology is giving the subject a fresh
direction. The message is plain: the understanding of
landforms must be based on knowledge of history and
process. Without an understanding of process, history
is undecipherable; without knowledge of history, pro-
cess lacks a context. Together, process and history lead
to better appreciation of the Earth's surface forms, their
behaviour and their evolution.
SUMMARY
Old landscapes, like old soldiers, never die. Geomorphic
processes, as effective as they are at reducing mountains
to mere monadnocks, fail to eliminate all vestiges of past
landforms in all parts of the globe. Old plains (palaeo-
plains) survive that are tens and hundreds of millions of
years old. These old plains may be peneplains formed
by fluvial action, pediplains and panplains formed by
scarp retreat and lateral planation by rivers respectively,
etchplains, or plains formed by marine erosion. Many
other landforms are antiques. Relict landforms survive
today under environmental conditions different from
those that created them. Examples are the tors and insel-
bergs in England and Wales. Some karst formed long
ago also survives to the present from times when the
environmental conditions were conducive to karst for-
mation. Exhumed landforms are old landforms that were
buried beneath a cover of sediments and then later re-
exposed as the cover rocks were eroded. Several exhumed
palaeoplains and such other landforms as reef knolls have
been discovered. Exhumed karst is also found. Stagnant
landscapes are geomorphic backwaters where little ero-
sion has occurred and the land surface has been little
altered for millions of years or far longer. They appear
to be more common than was once supposed. Several
geomorphologists, following in the footsteps of James
Hutton, favour a cyclical interpretation of land-surface
history. William Morris Davis and Lester King were
doughty champions of cyclical landscape changes. More
recently, ideas on the cyclical theme have included alter-
nating biostasis and rhexistasis, and, linking geomorphic
processes with plate tectonics, a cratonic regime model.
All landscapes are affected by environmental change.
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