scholarly journals Mixing as a driver of temporal variations in river hydrochemistry: 1. Insights from conservative tracers in the Andes-Amazon transition

2017 ◽  
Vol 53 (4) ◽  
pp. 3102-3119 ◽  
Author(s):  
Mark A. Torres ◽  
J. Jotautas Baronas ◽  
Kathryn E. Clark ◽  
Sarah J. Feakins ◽  
A. Joshua West
Keyword(s):  
Temporal Variations ◽  
The Andes ◽  
Conservative Tracers

scholarly journals Observations and dynamical implications of active normal faulting in South Peru

2020 ◽  
Vol 222 (1) ◽  
pp. 27-53 ◽  
Author(s):  
Sam Wimpenny ◽  
Carlos Benavente ◽  
Alex Copley ◽  
Briant Garcia ◽  
Lorena Rosell ◽  
...  
Keyword(s):  
Late Quaternary ◽  
Normal Fault ◽  
Temporal Variations ◽  
Alluvial Fan ◽  
Force Balance ◽  
Fault System ◽  
Normal Faults ◽  
Shear Stresses ◽  
Total Force ◽  
The Andes

SUMMARY Orogenic plateaus can exist in a delicate balance in which the buoyancy forces due to gravity acting on the high topography and thick crust of the plateau interior are balanced by the compressional forces acting across their forelands. Any shortening or extension within a plateau can indicate a perturbation to this force balance. In this study, we present new observations of the kinematics, morphology and slip rates of active normal faults in the South Peruvian Altiplano obtained from field studies, high-resolution DEMs, Quaternary dating and remote sensing. We then investigate the implications of this faulting for the forces acting on the Andes. We find that the mountains are extending ∼NNE–SSW to ∼NE–SW along a normal fault system that cuts obliquely across the Altiplano plateau, which in many places reactivates Miocene-age reverse faults. Radiocarbon dating of offset late Quaternary moraines and alluvial fan surfaces indicates horizontal extension rates across the fault system of between 1 and 4 mm yr–1—equivalent to an extensional strain rate in the range of 0.5–2 × 10−8 1 yr–1 averaged across the plateau. We suggest the rate and pattern of extension implies there has been a change in the forces exerted between the foreland and the Andes mountains. A reduction in the average shear stresses on the sub-Andean foreland detachment of ≲4 MPa (20–25 per cent of the total force) can account for the rate of extension. These results show that, within a mountain belt, the pattern of faulting is sensitive to small spatial and temporal variations in the strength of faults along their margins.

scholarly journals Intra- to Multidecadal Variations of Snowpack and Streamflow Records in the Andes of Chile and Argentina between 30° and 37°S

2010 ◽  
Vol 11 (3) ◽  
pp. 822-831 ◽  
Author(s):  
Mariano H. Masiokas ◽  
Ricardo Villalba ◽  
Brian H. Luckman ◽  
Steven Mauget
Keyword(s):  
Large Scale ◽  
Low Frequency ◽  
Temporal Variations ◽  
Regime Shifts ◽  
Positive Trend ◽  
River Flows ◽  
The Andes ◽  
The Pacific ◽  
Dry Conditions ◽  
Hydroclimatic Variability

Abstract In a recent study the authors developed the first regionally averaged, transnational records of snowpack and streamflow for the Andes between 30° and 37°S using Chilean and Argentinean data. That study was mainly intended to evaluate the relationships between the interannual variations in the regional snowpack record and large-scale atmospheric variables and indices. Here the focus is on the main intra- to multidecadal variations in updated records of winter snowpack and mean annual river flows. River discharges show similar temporal variations on both sides of the Andes with extreme dry conditions concentrated between the mid-1940s and 1976/77 and extreme wet conditions peaking between the late 1970s and the 1980s. A regional streamflow composite (1906–2007) has a nonsignificant negative trend but significant regime shifts in 1945, when mean levels dropped 31%, and in 1977 when they increased 28%. These events coincide almost exactly with well-known shifts in the Pacific decadal oscillation (PDO). The analyses are preliminary but suggest a PDO influence on the low-frequency modes of hydroclimatic variability in the study area. Analyses of the magnitude of 5–20-yr moving windows in the regional streamflow composite indicate that the most significant concentration of high (low) discharges occurred between 1977 and 1987 (1954 and 1971). Snowpack series show a more heterogeneous pattern of variations on a local basis but when aggregated into a regional series (1951–2008) they share remarkable similarities with river flows. However, the snowpack composite has a stronger year-to-year variability, a slight positive trend, and no significant regime shifts.

Bilaterality in the Andes

1977 ◽  
Author(s):  
Bernd Lambert
Keyword(s):  
The Andes

Strength through adversity — farmer-led irrigation in the Andes

Waterlines ◽  
1995 ◽  
Vol 13 (4) ◽  
pp. 12-14
Author(s):  
Gonzalo La Cruz
Keyword(s):  
The Andes
Sign in / Sign up

Export Citation Format

Share Document