Geology Reference
In-Depth Information
faults accelerate synchronously at the expense
of other faults? How large are the earthquake
ruptures that accommodate the stress that is
built by the incessant deformation of the crust?
In a chapter on paleoseismology, we discuss
some of the techniques for delineating the past
behavior of faults, defining recurrence intervals
and paleoslip rates, and assessing whether
earthquakes occur with temporal regularity or
randomness or in clusters.
Naturally, discovering ways to measure the
amount and rate of erosional losses from an area
and to define changes in the height of the surface
of that same area through time lies at the heart of
many tectonic-geomorphic studies. Armed with
new tools for dating and with digital topographic
databases, we can now address these topics more
accurately than in the past. In a chapter on ero-
sion and uplift, we describe several strategies for
quantification of rates of erosion, surface uplift,
and rock uplift, and we illustrate how these can
be synthesized to examine the balance between
building and tearing down of topography.
In the latter half of this topic, we step away
from a focus on the key building blocks and
instead introduce concepts and examples of
landscape evolution and tectonic interpretations
at different time scales. Moreover, rather than
examine specific geomorphic environments or
topics, such as the ways in which rivers and
fluvial features can provide insights on tectonic
processes, we focus on more integrated studies.
The key issues can be encompassed by two
questions: “What information from the Earth's
surface improves our understanding of the
nature of the interactions between tectonics
and geomorphological processes?” and “How do
we interpret preserved geomorphic features in
order to reveal rates and patterns of tectonic
deformation in the past?” The more recent
record is often best suited to answer the first
question, whereas great value comes from
studies that are able to answer the second
question for intervals in the distant past.
There is a natural, time-dependent progression
in the nature of tectonic-geomorphic landscapes
and the insights that can be gained from them.
Perhaps surprisingly, part of this progression
is  dictated by past climate changes (Fig. 1.1).
Holocene
Full
Interglacial
Scales of
Climate Change
Full
Glacial
10 4
0
One Climate Cycle
Full
Interglacial
Full
Glacial
10 5
0
A Million Years
Full
Interglacial
Full
Glacial
0 10 6
Years Before Present
Fig. 1.1 Schematic illustration of climate change
scaled at orders of magnitude (Holocene, one glacial
cycle, Middle-Late Pleistocene).
The relative stability of the Holocene climate is
atypical of a full glacial-interglacial, 100-kyr cycle.
Similarly, the sawtooth pattern of change during
past glacial-interglacial cycles does not show
oscillations of similar magnitude, as is typical of the
past million years.
At  Holocene time scales, we are confined to a
post-glacial era in which climatic conditions
have varied relatively little. At time scales of
100 000 years or more, complete or multiple
glacial-interglacial cycles have occurred.
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