Geoscience Reference
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Linkages Between Climate, Surface Processes, and Deeper Earth Processes
Although it has long been recognized that lower crust and mantle processes
can significantly influence landscape evolution, linkages between climate and deeper
Earth processes remain largely unexplored. Climate and tectonics are fundamentally
linked through the influence of sediment loading and erosion unloading on the state
of stress in Earth's interior that in turn govern tectonic motions. For example, the
development of large, high-elevation plateaus holds the potential for strong climate-
tectonic feedbacks through rapid, localized incision on plateau margins that receive
substantial precipitation. Such localized erosion creates the potential to advect hot,
low-viscosity, mid-to-lower crustal rocks to the surface in either channel flow along
laterally continuous belts or localized domal uplifts (e.g., Beaumont et al., 2001,
2004; Hodges et al., 2001; Koons et al., 2002; Zeitler et al., 2001). Rapid erosion in
such settings can lead to a positive feedback by drawing up highly pressurized ductile
rock toward the surface, resulting in isothermal decompression that may induce
partial melting that further reduces viscosity and resistance to flow. Because
deformation rates can respond to surface forcing with little time lag, the pace of
surface erosion can drive long-term patterns of structural deformation. The response
to climate variability of such tightly coupled erosion-tectonic systems has not been
explored and presents an attractive opportunity for future research.
Other examples of deeper Earth response to erosion unloading and sediment
loading of Earth's surface include the impact of sediment distribution on the
distribution and magnitudes of subduction zone megathrust earthquakes, with
important implications for the major human population centers located along
subducting margins (e.g., Wells et al., 2003). Recent studies reveal linkages between
climate and volcanic activity with increased volcanic activity during periods of
deglaciation (e.g., Sigvaldason et al., 1992; Jellinek et al., 2004) that are attributed to
enhanced decompression mantle melting due to glacial unloading (Jull and
Mackenzie, 1996; MacLennan et al., 2002). Release of carbon dioxide associated
with this enhanced subaerial volcanism during deglaciation may in turn play a
significant role in modulating glacial/interglacial cycles (Huybers and Langmuir,
2009).
Global patterns of sea-level rise are directly linked to elastic deformation of
the solid Earth and are another manifestation of the complex interactions between
Earth's interior and surface. There is particular concern that accelerated melting in the
modern warming world could lead to collapse of the West Antarctic Ice Sheet with
meter-scale rises in sea level worldwide. Highly non-uniform sea-level rise is
predicted with enhanced sea-level rise around North America as a result of the
interplay between changes in gravity due to the redistribution of ice/water and rock,
changes in Earth's rotation, and changes in shoreline geometry (see Figure 2.17).
In all of these research areas, significant opportunities exist for framing
testable hypotheses to guide field studies of the interactions between climate and
tectonics in landscape evolution. Of particular need are studies to evaluate temporal
variability. Given the different timescales of climate variability and deep Earth
processes, what are the sensitivities and lag times built into their interactions?
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