scholarly journals Climate controls on erosion in tectonically active landscapes

2020 ◽  
Vol 6 (42) ◽  
pp. eaaz3166 ◽  
Author(s):  
B. A. Adams ◽  
K. X. Whipple ◽  
A. M. Forte ◽  
A. M. Heimsath ◽  
K. V. Hodges
Keyword(s):  
Tectonic Evolution ◽  
Predictive Power ◽  
Annual Rainfall ◽  
Potential Influence ◽  
Ongoing Debate ◽  
Mountain Ranges ◽  
Erosion Rates ◽  
Tectonically Active ◽  
Climate Controls ◽  
The Himalaya

The ongoing debate about the nature of coupling between climate and tectonics in mountain ranges derives, in part, from an imperfect understanding of how topography, climate, erosion, and rock uplift are interrelated. Here, we demonstrate that erosion rate is nonlinearly related to fluvial relief with a proportionality set by mean annual rainfall. These relationships can be quantified for tectonically active landscapes, and calculations based on them enable estimation of erosion where observations are lacking. Tests of the predictive power of this relationship in the Himalaya, where erosion is well constrained, affirm the value of our approach. Our model allows estimation of erosion rates in fluvial landscapes using readily available datasets, and the underlying relationship between erosion and rainfall offers the promise of a deeper understanding of how climate and tectonic evolution affect erosion and topography in space and time and of the potential influence of climate on tectonics.

The Making of the Himalaya, Karakoram, and Tibetan Plateau

2013 ◽  
Author(s):  
Mike Searle
Keyword(s):  
Tibetan Plateau ◽  
Plate Boundary ◽  
Indian Plate ◽  
North West ◽  
Geological Interpretation ◽  
Mountain Ranges ◽  
The Road ◽  
The North ◽  
On The Road ◽  
The Himalaya

My quest to figure out how the great mountain ranges of Asia, the Himalaya, Karakoram, and Tibetan Plateau were formed has thus far lasted over thirty years from my first glimpse of those wonderful snowy mountains of the Kulu Himalaya in India, peering out of that swaying Indian bus on the road to Manali. It has taken me on a journey from the Hindu Kush and Pamir Ranges along the North-West Frontier of Pakistan with Afghanistan through the Karakoram and along the Himalaya across India, Nepal, Sikkim, and Bhutan and, of course, the great high plateau of Tibet. During the latter decade I have extended these studies eastwards throughout South East Asia and followed the Indian plate boundary all the way east to the Andaman Islands, Sumatra, and Java in Indonesia. There were, of course, numerous geologists who had ventured into the great ranges over the previous hundred years or more and whose findings are scattered throughout the archives of the Survey of India. These were largely descriptive and provided invaluable ground-truth for the surge in models that were proposed to explain the Himalaya and Tibet. When I first started working in the Himalaya there were very few field constraints and only a handful of pioneering geologists had actually made any geological maps. The notable few included Rashid Khan Tahirkheli in Kohistan, D. N. Wadia in parts of the Indian Himalaya, Ardito Desio in the Karakoram, Augusto Gansser in India and Bhutan, Pierre Bordet in Makalu, Michel Colchen, Patrick LeFort, and Arnaud Pêcher in central Nepal. Maps are the starting point for any geological interpretation and mapping should always remain the most important building block for geology. I was extremely lucky that about the time I started working in the Himalaya enormous advances in almost all aspects of geology were happening at a rapid pace. It was the perfect time to start a large project trying to work out all the various geological processes that were in play in forming the great mountain ranges of Asia. Satellite technology suddenly opened up a whole new picture of the Earth from the early Landsat images to the new Google Earth images.

Accelerated Erosion and Sedimentation in Southeast Asia

2005 ◽  
Author(s):  
Avijit Gupta
Keyword(s):  
Southeast Asia ◽  
Sediment Yield ◽  
Large Scale ◽  
Drainage Basin ◽  
High Rate ◽  
Annual Rainfall ◽  
Sediment Yields ◽  
Erosion Rates ◽  
Sediment Transfer ◽  
Very High

Periodic attempts to plot global distribution of erosion and sedimentation usually attribute most of Southeast Asia with a very high sediment yield (Milliman and Meade 1983). The erosion rates and sediment yield figures are especially high for maritime Southeast Asia. Milliman and Syvitski (1992), for example, listed 3000 t km−2 yr−1 for the archipelagos and peninsulas of Southeast Asia. They provided a number of natural explanations for the high erosion rate: location near active plate margins, pyroclastic eruptions, steep slopes, and mass movements. This is also a region with considerable annual rainfall, a very substantial percentage of which tends to be concentrated in a few months and falls with high intensity. Part of Southeast Asia (the Philippines, Viet Nam, Timor) is visited by tropical cyclones with heavy, intense rainfall and possible associated wind damage to existing vegetation. The fans at the foot of slopes, the large volume of sediment stored in the channel and floodplain of the rivers, and the size of deltas all indicate a high rate of erosion and episodic sediment transfer. This episodic erosion and sediment transfer used to be controlled for most of the region by the thick cover of vegetation that once masked the slopes. When vegetation is removed soil and regolith de-structured, and natural slopes altered, the erosion rates and sediment yield reach high figures. Parts of Southeast Asia display striking anthropogenic alteration of the landscape, although the resulting accelerated erosion may be only temporary, operating on a scale of several years. Over time the affected zones shift, and slugs of sediment continue to arrive in a river but from different parts of its drainage basin. The combination of anthropogenic alteration and fragile landforms may give rise to very high local yields. Sediment yields of more than 15 000 t km−2 yr−1 have been estimated from such areas (Ruslan and Menam, cited in Lal 1987). This is undoubtedly towards the upper extreme, but current destruction of the vegetation cover due to deforestation, expansion of agriculture, mining, urbanization, and implementation of large-scale resettlement schemes has increased the sediment yield from < 102 to > 103 t km−2 yr−1.

Propagating uplift controls on formation of low-relief, high-elevation surfaces in the SE Tibetan Plateau

2020 ◽  
Author(s):  
Xiaoping Yuan ◽  
Kimberly Huppert ◽  
Jean Braun ◽  
Laure Guerit
Keyword(s):  
Tibetan Plateau ◽  
High Elevation ◽  
Step Change ◽  
Loss Mechanism ◽  
Mountain Ranges ◽  
Horizontal Advection ◽  
Erosion Rates ◽  
Relief Surface ◽  
Deposition Processes ◽  
Three Rivers

&lt;p&gt;The SE Tibetan Plateau has extensive broad, low-relief, high-elevation surfaces perched above deep valleys, as well as in the headwaters of the three rivers (the Salween, the Mekong, and the Yangtze). However, understanding the presence of these low-relief surfaces is a long-standing challenge because their formation process remains highly debated. While alternate mechanisms have been proposed to explain the low-relief surface formation in this setting (e.g., drainage-area loss mechanism due to horizontal advection; Yang et al., 2015, Nature), a long-standing hypothesis for the formation of low-relief surfaces is by a step change in uplift and incision into a pre-existing, low-relief surface (Clark et al., 2006, JGR; Whipple et al., 2017, Geology).&lt;/p&gt;&lt;p&gt;The morphology of low-relief surfaces in the SE Tibetan Plateau is largely consistent with formation by a step change in uplift, but one problem with this model is that low-relief surfaces formed by a step change in uplift are relatively short-lived, since they are incised and steepened by erosion, which sweeps upstream at the response time of mountain ranges (in the order of several million years). Using a landscape evolution model that combines erosion, sediment transport and deposition processes (Yuan et al., 2019, JGR), we demonstrate that propagating uplift form large parallel rivers, with broad low-relief, high-elevation interfluves that persist for tens to hundreds of million years, consistent with various dated ages. These low-relief surfaces can be long-lived because the drainage areas in these interfluves are insufficient to keep up with rapid incision of the large parallel mainstem rivers. Our simulated features match various observations in the SE Tibetan Plateau: (i) low-relief surfaces are approximately co-planar in headwaters, and decrease in elevation smoothly from northwest to southeast across the plateau margin; (ii) &amp;#967;-elevation plots of the mainstem rivers are convex; (iii) low-relief surfaces have low erosion rates; and (iv) erosion rates are high in the mainstem rivers at the propagating margin.&lt;/p&gt;

Topographic evolution of mountain belts controlled by rheology and surface process efficiency

2020 ◽  
Author(s):  
Sebastian G. Wolf ◽  
Ritske S. Huismans ◽  
Jean Braun ◽  
Xiaoping Yuan
Keyword(s):  
Steady State ◽  
Process Efficiency ◽  
Surface Process ◽  
Tight Coupling ◽  
Active Growth ◽  
Term Survival ◽  
Erosion Rates ◽  
Mountain Belt ◽  
Tectonically Active ◽  
Mountain Belts

&lt;p&gt;It has been a long-standing problem how mountain belts gain and loose topography during their tectonically active growth and inactive decay phase. It is widely recognized that mountain belt topography is generated by crustal shortening, and lowered by river bedrock erosion, linking climate to tectonics. However, it remains enigmatic how to reconcile high erosion rates in active orogens as observed in Taiwan or New Zealand, with long term survival of topography for 100s of Myrs as observed for example in the Uralides and Appalachians. Here we use for the first time a tight coupling between a landscape evolution model (FastScape) with an upper mantle scale tectonic (thermo-mechanical) model to investigate the different stages of mountain belt growth and decay. Using two end-member models, we demonstrate that growing orogens with high erosive power remain small (&lt;200 km), reach steady state between tectonic in- and erosional material eff-flux, and are characterized by transverse valleys. Contrarily, mountain belts with medium to low erosive power will not reach growth steady state, grow wide, and are characterized by longitudinal rivers deflected by active thrusting. However, during growth both types of orogens reach the same height, controlled by rheology and independent of surface process efficiency. Erosional efficiency controls orogenic decay, which is counteracted by regional isostatic rebound. Rheological control of mountain height implies that there is a natural upper limit for the steepness index of rivers on Earth. To compare model results to various natural examples, we quantify the degree of longitudinal flow of modeled rivers with river &amp;#8220;longitudinality&amp;#8221; in several active or recently active orogens on Earth. Application of the river &amp;#8220;longitudinality index&amp;#8221; gives information whether (parts of) an orogen is or was at steady state during orogenic growth.&lt;/p&gt;

What controls erosion (exhumation) along the humid eastern margin of the Northern Andes? Insights from U-Th/He thermochronology

2020 ◽  
Author(s):  
Nicolas Perez-Consuegra ◽  
Edward R Sobel ◽  
Andres Mora ◽  
Jose R Sandoval ◽  
Paul G Fitzgerald ◽  
...  
Keyword(s):  
Middle Part ◽  
Tropical Regions ◽  
Northern Andes ◽  
Mountain Ranges ◽  
Mountainous Regions ◽  
Relative Contribution ◽  
Tectonically Active ◽  
Exhumation Rates ◽  
High Precipitation ◽  
Channel Steepness

&lt;p&gt;The relative controls of rock uplift (tectonics) and precipitation (climate) on the exhumation of earth&amp;#8217;s rocks in tectonically active mountain ranges are still debated. In low latitude tropical regions where rates of precipitation and the amount of vegetation cover are higher, more data is required to test the relative contribution of these factors to the evolution of orogenic topography. To contribute to this debate, cooling ages were derived for 25 bedrock and four detrital samples using the apatite (U-Th-Sm)/He (AHe) low temperature thermochronometer. AHe ages are reported along a ~450-km-wide swath on the eastern flank of the Northern Andes in Colombia (South America). The AHe cooling ages, that range from 2.5 Ma to 17 Ma, are compared to precipitation rates and geomorphic parameters in order to discern the relative importance of climate and/or tectonics on exhumation. Along the transect, AHe cooling ages are poorly correlated with the rates of precipitation but show a good correlation with landscape parameters such as average hillslope and average channel steepness. Moreover, young AHe cooling ages coincide with areas where deformation is mainly compressional; older AHe cooling ages are found in the middle part of the study area where strike-slip deformation dominates. The spatial distribution of the new AHe cooling ages suggests that in mountainous regions, in this case with high precipitation rates (&gt; 1500 mm/yr), denudation is mainly controlled by the rate of vertical advection of material via tectonic processes. The spatial variations in precipitation may only have a second-order role in modulating exhumation rates.&lt;/p&gt;

scholarly journals Landslide Erosion Rate in the Eastern Cordillera of Northern Bolivia

2007 ◽  
Vol 11 (19) ◽  
pp. 1-30 ◽  
Author(s):  
Troy A. Blodgett ◽  
Bryan L. Isacks
Keyword(s):  
Erosion Rate ◽  
Aerial Photographs ◽  
Field Surveys ◽  
Bedrock Rivers ◽  
Eastern Cordillera ◽  
Erosion Rates ◽  
Landslide Volume ◽  
Tectonically Active ◽  
Dominant Process ◽  
Very High

Abstract The northeastern edge of the Bolivian Eastern Cordillera is an example of a tectonically active plateau margin where orographically enhanced precipitation facilitates very high rates of erosion. The topography of the steepest part of the margin exhibits the classic signature of high erosion rates consisting of high-relief V-shaped valleys where landsliding is the dominant process of hillslope erosion and bedrock rivers are incising into the landscape. The authors mapped landslide scars on multitemporal aerial photographs to estimate hillslope erosion rates. Field surveys of landslide scars are used to calibrate a landslide volume versus area relationship. The mapped area of landsliding, in combination with an estimate of the time for landslide scars to revegetate, leads to an erosion rate estimate. The estimated revegetation time, 10–35 yr, is based on analysis of multitemporal aerial photographs and tree rings. About 4%–6% of two watersheds in the region considered were affected by landslides over the last 10–35 yr. This result implies an erosion rate of 9 ± 5 mm yr−1 assuming that 90% of a single landslide reaches the river on average. Classified Landsat Thematic Mapper images show that landslides are occurring at approximately the same rate all across an approximately 40-km-wide swath within the high-relief zones of the cordillera.

scholarly journals Hillslopes Record the Growth and Decay of Landscapes

Science ◽  
2013 ◽  
Vol 341 (6148) ◽  
pp. 868-871 ◽  
Author(s):  
Martin D. Hurst ◽  
Simon M. Mudd ◽  
Mikael Attal ◽  
George Hilley
Keyword(s):  
United States ◽  
Numerical Modeling ◽  
Nonlinear Diffusion ◽  
Vertical Displacement ◽  
Back Pressure ◽  
Erosion Rates ◽  
Pressure Ridge ◽  
Tectonically Active ◽  
History Of ◽  
Uplift History

Earth's surface archives the combined history of tectonics and erosion, which tend to roughen landscapes, and sediment transport and deposition, which smooth them. We analyzed hillslope morphology in the tectonically active Dragon’s Back Pressure Ridge in California, United States, to assess whether tectonic uplift history can be reconstructed using measurable attributes of hillslope features within landscapes. Hilltop curvature and hillslope relief mirror measured rates of vertical displacement caused by tectonic forcing, and their relationships are consistent with those expected when idealizing hillslope transport as a nonlinear diffusion process. Hilltop curvature lags behind relief in its response to changing erosion rates, allowing growing landscapes to be distinguished from decaying landscapes. Numerical modeling demonstrates that hillslope morphology may be used to infer changes in tectonic rates.

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