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

<p>The relative controls of rock uplift (tectonics) and precipitation (climate) on the exhumation of earth’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 (> 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.</p>

Invasive Syzygium jambos trees in Puerto Rico: no refuge from guava rust

2017 ◽  
Vol 33 (3) ◽  
pp. 205-212 ◽  
Author(s):  
Erin Burman ◽  
James D. Ackerman ◽  
Raymond L. Tremblay
Keyword(s):  
Puerto Rico ◽  
Species Distribution Modelling ◽  
Negative Consequences ◽  
Tropical Regions ◽  
Mountainous Regions ◽  
Syzygium Jambos ◽  
Guava Rust ◽  
Invasive Tree ◽  
High Precipitation ◽  
Austropuccinia Psidii

Abstract:Biological invasions can have negative consequences for resident biota, particularly when disease-causing organisms are involved. Austropuccinia psidii, or guava rust, has rapidly spread through the tropics affecting both native and non-native Myrtaceae. In Puerto Rico, the rust has become common on Syzygium jambos, an invasive tree native to South-East Asia. What are the drivers of infection, and do refugia exist across a heterogeneous landscape? We address these questions using species distribution modelling and beta regressions. The realized and potential distribution of Syzygium jambos is extensive. The model produced an AUC of 0.88, with land-use categories and precipitation accounting for 61.1% of the variation. Predictability of S. jambos is highest in disturbed habitats, especially in mountainous regions with high precipitation. All 101 trees surveyed and measured across Puerto Rico showed signs of infection to varying extents. Infection severity was consistently associated with annual mean temperature in all top beta regression models, but was also commonly associated with tree size and precipitation variables. We found no safe sites for S. jambos. Many trees were extremely unhealthy and some were dead, suggesting that S. jambos may soon become extinct on the island or reduced to persistent stump sprouts. Native vegetation may benefit from the local demise of S. jambos. While the rust has not jumped to native Myrtaceae, vigilance is required, as host-shifts have occurred in other tropical regions.

Climate as the great equalizer of continental-scale erosion

2021 ◽  
Author(s):  
Gilby Jepson ◽  
Barbara Carrapa ◽  
Jack Gillespie ◽  
Ran Feng ◽  
Peter DeCelles ◽  
...  
Keyword(s):  
Central Asia ◽  
Regional Scale ◽  
Continental Scale ◽  
Active Tectonic ◽  
Tectonically Active ◽  
High Precipitation ◽  
Tectonic Boundaries ◽  
Great Equalizer ◽  
Tian Shan

<p>Central Asia is one of the most tectonically active and orographically diverse regions in the world and is the location of the highest topography on Earth resulting from major plate tectonic collisional events. Yet the role of tectonics versus climate on erosion remains one of the greatest debates of our time. We present the first regional scale analysis of 2526 published low-temperature thermochronometric dates from Central Asia spanning the Altai-Sayan, Tian Shan, Tibet, Pamir, and Himalaya. We compare these dates to tectonic processes (proximity to tectonic boundaries, crustal thickness, seismicity) and state-of-the-art paleoclimate simulations in order to constrain the relative influences of climate and tectonics on the topographic architecture and erosion of Central Asia. Predominance of pre-Cenozoic ages in much of the interior of central Asia suggests that significant topography was created prior to the India-Eurasia collision and implies limited subsequent erosion. Increasingly young cooling ages are associated with increasing proximity to active tectonic boundaries, suggesting a first-order control of tectonics on erosion. However, areas that have been sheltered from significant precipitation for extensive periods of time retain old cooling ages. This suggests that ultimately climate is the great equalizer of erosion. Climate plays a key role by enhancing erosion in areas with developed topography and high precipitation such as the Tian Shan and Altai-Sayan during the Mesozoic and the Himalaya during the Cenozoic. Older thermochronometric dates are associated with sustained aridity following more humid periods.</p>

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.

scholarly journals Wind Speeds at Heights Crucial for Wind Energy: Measurements and Verification of Forecasts

2012 ◽  
Vol 51 (9) ◽  
pp. 1602-1617 ◽  
Author(s):  
Susanne Drechsel ◽  
Georg J. Mayr ◽  
Jakob W. Messner ◽  
Reto Stauffer
Keyword(s):  
Wind Speed ◽  
Low Cost ◽  
Good Choice ◽  
Mountainous Regions ◽  
Wind Speeds ◽  
Relative Contribution ◽  
Site Characteristics ◽  
One Year ◽  
Nwp Model ◽  
Ecmwf Model

AbstractWind speed measurements from one year from meteorological towers and wind turbines at heights between 20 and 250 m for various European sites are analyzed and are compared with operational short-term forecasts of the global ECMWF model. The measurement sites encompass a variety of terrain: offshore, coastal, flat, hilly, and mountainous regions, with low and high vegetation and also urban influences. The strongly differing site characteristics modulate the relative contribution of synoptic-scale and smaller-scale forcing to local wind conditions and thus the performance of the NWP model. The goal of this study was to determine the best-verifying model wind among various standard wind outputs and interpolation methods as well as to reveal its skill relative to the different site characteristics. Highest skill is reached by wind from a neighboring model level, as well as by linearly interpolated wind from neighboring model levels, whereas the frequently applied 10-m wind logarithmically extrapolated to higher elevations yields the largest errors. The logarithmically extrapolated 100-m model wind reaches the best compromise between availability and low cost for data even when the vertical resolution of the model changes. It is a good choice as input for further statistical postprocessing. The amplitude of measured, height-dependent diurnal variations is underestimated by the model. At low levels, the model wind speed is smaller than observed during the day and is higher during the night. At higher elevations, the opposite is the case.

Influence of a glacial buzzsaw on the height and morphology of the Cascade Range in central Washington State, USA

2006 ◽  
Vol 65 (1) ◽  
pp. 96-107 ◽  
Author(s):  
Sara Gran Mitchell ◽  
David R. Montgomery
Keyword(s):  
Washington State ◽  
Cascade Range ◽  
Stream Power ◽  
Glacial Erosion ◽  
Spatial Gradients ◽  
Hypsometric Analysis ◽  
Erosion Models ◽  
Exhumation Rates ◽  
High Precipitation ◽  
Hillslope Processes

AbstractAnalysis of climatic and topographic evidence from the Cascade Range of Washington State indicates that glacial erosion limits the height and controls the morphology of this range. Glacial erosion linked to long-term spatial gradients in the ELA created a tilted, planar zone of 373 cirques across the central part of the range; peaks and ridges now rise ≤600 m above this zone. Hypsometric analysis of the region shows that the proportion of land area above the cirques drops sharply, and mean slopes >30° indicate that the areas above the cirques may be at or near threshold steepness. The mean plus 1σ relief of individual cirque basins (570 m) corresponds to the ∼600-m envelope above which peaks rarely rise. The summit altitudes are set by a combination of higher rates of glacial and paraglacial erosion above the ELA and enhanced hillslope processes due to the creation of steep topography. On the high-precipitation western flank of the Cascades, the dominance of glacial and hillslope erosion at altitudes at and above the ELA may explain the lack of a correspondence between stream-power erosion models and measured exhumation rates from apatite (U-Th/He) thermochronometry.

scholarly journals Statistical descriptive analysis of three climate variables; Precipitation, temperature and relative humidity. Study cases (Innaouene watershed; Morocco)

2021 ◽  
Vol 314 ◽  
pp. 03004
Author(s):  
Zineb Moumen ◽  
Ismail Elhassnaoui ◽  
Fatima Daid
Keyword(s):  
Relative Humidity ◽  
Descriptive Analysis ◽  
Seasonal Fluctuation ◽  
Middle Part ◽  
Climate Variable ◽  
Precipitation Temperature ◽  
High Precipitation ◽  
Lower Temperature ◽  
Variable Precipitation ◽  
Topographic Variation

Hydrological data are mandatory for the elaboration of studies related to water management. Statistical analysis is a crucial step for the grasping of the distribution of data range. The presented study consists on applying statistical descriptive analysis on three climate variable; precipitation, temperature and relative humidity. Two gages stations were used; Bab Marzouka and Idriss First in Innaouène watershed. The obtained results underlines that the temporal variation exposes an overall rising trend in the temperature and a decreasing trend in the rainfall and relative humidity over the fours studied decades, it also uncovers the intra-seasonal fluctuation, humid and rainy in the winter and sec and dry in the summer, the autumn and the spring are considered as transition season where the temperature is moderated. The spatial variation is marked by a slight decreasing in precipitation and increasing of temperature moving from the middle part of the watershed to the downstream, which could be explained by the topographic variation and its impact on the climate. High altitude are generally marked by high precipitation and lower temperature comparing to lowlands areas.

scholarly journals Global hotspots of recent and ancestral turnover in birds

2020 ◽  
Author(s):  
Ian R. McFadden ◽  
Marco Túlio P. Coelho ◽  
Rafael O. Wüest ◽  
Fernanda A. S. Cassemiro ◽  
Niklaus E. Zimmermann ◽  
...  
Keyword(s):  
Bird Species ◽  
Global Scale ◽  
Climatic Variation ◽  
Future Research ◽  
Niche Conservatism ◽  
Tropical Regions ◽  
Tropical Mountains ◽  
Biodiversity Research ◽  
Relative Contribution ◽  
Ancient Lineage

Abstract A primary goal of biodiversity research is to uncover the processes acting in space and time to create the global distribution of species richness. However, we currently lack an understanding of how recent versus ancient biodiversity dynamics shape patterns of diversity for most groups. Here, we introduce a method to partition lineage turnover into recent and ancestral components, and use it to identify hotspots of turnover at the global scale for 8,296 bird species. Counter to the tropical niche conservatism hypothesis, we find extra-tropical regions such as Greenland and the Sahara are hotspots of ancestral turnover, while areas with high climatic variation such as (sub)tropical mountains and biome transitions are recent turnover hotspots. We can now quantify the relative contribution of contemporary and ancient lineage dynamics to assemblage structure, which enables future research to explore the processes generating earth’s diversity in a more temporally-explicit framework.

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