Abstract
AbstractFractures are discontinuities in rock that can be exploited by erosion. Fractures regulate cohesion, profoundly affecting the rate, style, and location of Earth surface processes. By modulating the spatial distribution of erodibility, fractures can focus erosion and set the shape of features from scales of fluvial bedforms to entire landscapes. Although early investigation focused on fractures as features that influence the orientation and location of landforms, recent work has started to discern the mechanisms by which fractures influence the erodibility of bedrock. As numerical modeling and field measurement techniques improve, it is rapidly becoming feasible to determine how fractures influence geomorphic processes, as opposed to when or where. However, progress is hampered by a lack of research coordination across scales and process domains. We review studies from hillslope, glacial, fluvial, and coastal domains from the scale of reaches and outcrops to entire landscapes. We then synthesize this work to highlight similarities across domains and scales and suggest knowledge gaps, opportunities, and methodological challenges that need to be solved. By integrating knowledge across domains and scales, we present a more holistic conceptualization of fracture influences on geomorphic processes. This conceptualization enables a more unified framework for future investigation into fracture influences on Earth surface dynamics. © 2018 John Wiley & Sons, Ltd.
Highlights
Earth’s surface can be characterized on a broad scale by discontinuities, or fractures, which separate otherwise continuous Earth materials
In the realm of processes that are viewed as being directly impacted by fractures, this effort has led to important conceptualizations and models of processes such as fluvial plucking (Chatanantavet and Parker, 2009; Lamb et al, 2015), glacial quarrying (Hallet, 1996), coastal erosion (Naylor and Stephenson, 2010), and hillslope stability (Clarke and Burbank, 2010; Loye et al, 2012)
Orientation, and anisotropy at the hillslope and valley scale set the maximum size of sediment delivered downslope to rivers and glaciers (Sklar et al, 2017). This sediment acts as tools and cover in fluvial erosion (Sklar and Dietrich, 2004), but a strong link between fracture spacing and the eventual size of sediment delivered to rivers has yet to be determined, mainly due to the myriad of breakdown processes that occur between the production of sediment from bedrock and its eventual transport to the channel
Summary
Earth’s surface can be characterized on a broad scale by discontinuities, or fractures, which separate otherwise continuous Earth materials. In the realm of processes that are viewed as being directly impacted by fractures, this effort has led to important conceptualizations and models of processes such as fluvial plucking (Chatanantavet and Parker, 2009; Lamb et al., 2015), glacial quarrying (Hallet, 1996), coastal erosion (Naylor and Stephenson, 2010), and hillslope stability (Clarke and Burbank, 2010; Loye et al, 2012). In these domains, progress has been made to the point of being able to rudimentarily model fractures acting as controls on the rate, style, and spatial occurrence of geomorphic processes.
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